IPM practitioner Joe Barcinas with IPM researcher Joseph Morse

Citrograph 

March/April 2012 

Citrograph 

IPM practitioner 

Joe Barcinas 

with IPM researcher 

Joseph Morse 

CITRUS RESEARCH BOARD, P.O. Box 230, Visalia, CA 93279 

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CRP0112MOVENT0222-R00

Citrograph 

MARCH/APRIL 2012 • Volume 3 • Number 2 

Cover photo by Iqbal Pittalwala, UC Riverside 

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An Official Publication of the Citrus Research Board 

IN THIS ISSUE 

4 Editorial 

6 CCM Showcase, Protecting our Future 

10 Industry Views 

12 Proper monitoring and management 

of California Red Scale in the San 

Joaquin Valley 

22 Management of citrus thrips to reduce 

the evolution of resistance 

32 The evolution of biologically-based 

Integrated Pest Management in 

California citrus: history and perspective 

44 What are the University of California 

sources for citrus integrated pest 

management information 

48 CRB 2011Annual Report 

50 California Citrus Spurred Colonization– 

Aided Through the University of California... 

54 Reagentless detection of citrus pathogens 

using differential mobility spectrometry 

58 Celebrating Citrus 

Citrograph is published bimonthly by the Citrus Research Board, 217 N. Encina, Visalia, CA 93291. Citrograph is sent to all 

California citrus producers courtesy of the Citrus Research Board. If you are currently receiving multiple copies, or would like 

to make a change in your Citrograph subscription, please contact the publication office (above, left). 

Every effort is made to ensure accuracy in articles published by Citrograph; however, the publishers assume no responsibility 

for losses sustained, allegedly resulting from following recommendations in this magazine. Consult your local authorities. 

The Citrus Research Board has not tested any of the products advertised in this publication, nor has it verified any of the 

statements made in any of the advertisements. The Board does not warrant, expressly or implicitly, the fitness of any product 

advertised or the suitability of any advice or statements contained herein. 

March/April 2012 Citrograph 3

EDITORIAL 

BY TED A. BATKIN, President, Citrus Research Board 

Don’t let the background noise drown out the music 

This again shows how 

important it is to work 

with accurate information 

and how important a 

good communications 

system is in providing 

growers accurate, 

up-to-date information. 

In a previous life, I studied classical music and received a BA degree 

in conducting. One of the jobs of the conductor is to separate out 

the noise from the true music and bring all the musicians together 

to produce a harmonic sound. 

It is the same today in life as we attempt to keep focused on the 

true mission of the research and development programs for the California 

citrus growers. All too often, this effort is clouded by background 

noise from sectors with their own agendas and priorities. 

Such is the case with the recent reporting of an ACP in a trap in the 

San Joaquin Valley. The background noise in this event was deafening, 

and the true picture of what actually happened became drowned out 

in a myriad of false reports from many sectors in the media. 

In truth, there was a portion of an ACP found sticking to a trap 

from the glassy-winged sharpshooter program. The piece was DNA 

tested and found to be an Asian citrus psyllid. This event triggered action 

by CDFA to provide delimitation trapping grids and tree-by-tree 

ground surveys to determine if a breeding population existed in the 

area. When the additional efforts came up negative, the Department 

correctly identified the find as a “Regulatory Event” and closed the 

book on the issue. Delimitation will continue in the area, but no further 

quarantine action will take place. 

This event should serve as a reminder of just how vulnerable we 

are to specific actions. First, it proved the value of the constant trapping 

program being conducted by the industry in the commercial 

areas of the state to serve as an early warning system of ACP populations. 

The fact that there had not been any previous ACP detections 

played into the decision process to determine a potential 

quarantine. 

Second, it shows how easy it could be for an ACP to move into 

the San Joaquin Valley and how we need to be sure to have adequate 

contingency plans for ACP populations in the area. Do 

you have your plan in place 

Finally, it again shows how important it is to work with accurate 

information and how important a good communications 

system is in providing growers accurate, up-to-date information 

when a true infestation occurs. The industry will continue to develop 

better systems for informing all growers of the threat and any 

actual ACP populations that are detected, including what to do and 

how to do it. 

Your industry leaders are constantly working on this through all of 

the organizations that serve the growers. Just remember to sort out all 

the background noise and listen for the real music. l 

4 Citrograph March/April 2012

The Mission of the Citrus Research Board: 

Develop knowledge and build systems for grower vitality. 

Focus on quality assurance, clonal protection, production research, 

variety development, and grower/public education. 

CITRUS RESEARCH BOARD MEMBER LIST BY DISTRICT 2011-2012 

District 1 – Northern California 

Member 

Alternate 

Allan Lombardi, Exeter Justin Brown, Orange Cove 

Donald Roark, Lindsay Dan Dreyer, Exeter 

Jim Gorden, Exeter 

Dan Galbraith, Porterville 

Joe Stewart, Bakersfield Franco Bernardi, Visalia 

Etienne Rabe, Bakersfield Richard Bennett, Visalia 

John Richardson, Porterville Jeff Steen, Strathmore 

Kevin Olsen, Pinedale Tommy Elliott, Visalia 

District 2 – Southern California – Coastal 

Member 

Alternate 

Earl Rutz, Pauma Valley Alan Washburn, Riverside 

William Pidduck, Santa Paula James Finch, Santa Paula 

Joe Barcinas, Riverside Warren Lyall, Pauma Valley 

District 3 – California Desert 

Member 

Mark McBroom, Calipatria 

Public Member 

Member 

Seymour Van Gundy, Riverside 

Alternate 

Craig Armstrong, Thermal 

Alternate 

Steve Garnsey, Fallbrook 

Citrus Research Board 

217 N Encina, Visalia, CA 93291 

PO Box 230, Visalia, CA 93279 

(559) 738-0246 

FAX (559) 738-0607 

E-Mail Info@citrusresearch.org 

CALENDAR 

May 2 

May 2 

June 28 

August 21-23 

September 18 

October 10-11 

November 1 

CRB/CPDPP Joint Operations Committee Meeting 

CRB Conference Room – Visalia 

CPDPP Outreach Subcommittee Meeting 

CRB Conference Room – Visalia 

CRB Board Meeting 

Four Points by Sheraton – Ventura 

CRB Research – Review of Proposals 

DoubleTree Hotel – Bakersfield 

CRB Annual Meeting 

Lindcove REC 

California Citrus Conference 

Porterville Fairgrounds – Porterville 

CCM Annual Meeting 

For more information on the above, contact the CRB office at 

(559) 738-0246. 

DO YOU KNOW... 

What happened in California 40 years ago that 

still impacts pest management operations today 

(Turn to the inside back cover for the answer.) 


‘We are laying out our unified plan 

to control the disease’ 

We need to be ready 

and will be. 

—Robert Leavitt 

Photo by Lynn Sanderson 

Editor’s Note: The following message from CDFA’s Dr. Robert Leavitt is a 

digest of the remarks he made at the 2012 Citrus Showcase, where he was a luncheon 

speaker and workshop panelist. 

A storm is coming to California citrus—huanglongbing (HLB), or citrus 

greening. History tells us it’s just a matter of time before the disease is detected 

here. It has always followed its vector, the Asian citrus psyllid, which has been 

in California since 2008.At the moment, we know HLB is inching closer after 

detections in Baja California, Mexico, and Texas. 

So we believe that, sooner or later, HLB will be here. Under the leadership 

of California Department of Food and Agriculture Secretary Karen Ross, we 

are laying out our unified plan to control the disease when the time comes. The 

need to protect citrus groves and residential trees is paramount. We are acutely 

aware of the risk to fresh and export markets and are doing all that is possible 

to secure those markets. 

Working with the USDA, local Ag Commissioners, the Citrus Research 

Board, and the federal office of Customs and Border Protection, and utilizing 

the best scientific and technical advice available, CDFA is presenting a plan 

with several key points: 

1). Screen citrus mother trees so clean, disease-free stock may be planted. 

2). Use robust surveying and detection in harmony with quarantine regulations 

to restrict the movement of host material. 

3). Control, suppress and, where possible, eradicate psyllids. 

4). Area-wide treatment programs in both residential and commercial citrus. 

5). Removal of residential and commercial trees infected with HLB. 

This is the greatest challenge California’s citrus industry will face. We need 

to be ready and will be. We appreciate your support as we all move forward 

together in a program that is a model for public-private cooperation. 

Robert Leavitt, Ph.D., is Director of the California Department of Food 

and Agriculture’s Plant Health Division. l 

CCM’s 2012 Citrus Showcase 

‘Protecting our citrus, protecting our future’ 

On March 8, hundreds of growers along with packers 

and other members of the industry converged 

on the Visalia Convention Center for California Citrus 

Mutual’s Citrus Showcase. 

“Protecting our citrus, protecting our future” was the 

theme for this Showcase, and at no time during the day 

was that theme more appropriate than at the luncheon 

when Dr. Robert Leavitt of CDFA addressed the crowd 

on the subject of Asian citrus psyllid and huanglongbing. 

(See ‘laying out our unified plan’ above.) 

The audience also heard from attorney and ag advocate 

George Soares, managing partner of Kahn, Soares 

& Conway, who gave an update on State politics, offered 

insights into the “personality” of Sacramento, and shared 

thoughts on becoming more effective in dealings with 

government given today’s political climate. 

6 Citrograph March/April 2012 

The program included three workshops, each with a 

panel presentation and then follow-up Q&A, on meeting 

food safety requirements and expectations, evaluating 

the impact of this season’s frost events (especially the toll 

on mandarins), and the latest information on ACP/HLB. 

The trade show portion of the event had 70 exhibitors 

including the Citrus Research Board and the CP- 

DPP. Sponsors of the 2012 Citrus Showcase were Bayer 

Crop Science, Dow AgroSciences, Farm Credit Associations, 

Fruit Growers Supply Company, Sinclair Systems 

International, Southern California Edison, Syngenta 

Crop Protection, Valent USA, and Yara North America. 

The workshops were sponsored by Amvac Chemical 

Corporation and Capital Agricultural Property Services, 

Inc., and the continental breakfast was hosted by Mary 

Roach Insurance. l


ABOUT THE COVER 

For the cover of this issue featuring Integrated Pest Management, 

we chose orange grower and CRB Board member 

Joe Barcinas, who operates an insectary and is a pest 

control advisor, and research entomologist Dr. Joseph Morse, 

professor in the Department of Entomology at UC Riverside, 

whose work is focused on pests of citrus and avocado. 

Shown here is the Morse lab team, left to right (with their 

years in the lab in parentheses): 40%-time administrative 

specialist Heavenly Clegg (18), Morse, lab assistant Pam Watkins 

(30, retiring June 2012), SRA Alan Urena (33), and SRA 

Lindsay Robinson (28). Clegg and Watkins are holding a tray 

of waxed lemons used for armored scale colonies. 

Barcinas, who is based in Riverside, has worked for over 

25 years as a PCA and IPM practitioner for Entomological 

Services, Inc. Today, Joe and fellow PCA Robert Walther are 

business partners in ESI and also as navel growers in the San 

Joaquin Valley. Barcinas is also the owner of Foothill Agricultural 

Research, Inc. in Corona, producing Aphytis melinus, 

Anagyrus pseudococci, Cryptolaemus, decollate snails, and 

brown lacewing. 

Photo by Iqbal Pittalwala, UC Riverside. 

Getting to the core of the matter 

CRB research program implements ‘Core Programs’ 

Anyone who has ever attended the March meetings 

at which scientists present the progress made on 

their CRB-funded research projects knows how mentally 

draining these few days are. Furthermore, the time limit 

placed on the length of the presentations does not do 

justice to our long-term programs such as the Integrated 

Pest Management (IPM), breeding, and variety evaluation 

programs. Despite the best efforts of Drs. Beth Grafton- 

Cardwell, Tracy Kahn, Joe Morse, and Mike Roose to interact 

with the Board for guidance and direction, there is 

not sufficient time for the board to focus on their questions 

and issues. 

To improve this situation, the Board and research 

committee members decided to separate these extended 

projects from the one- to three-year projects of limited 

scope and identify them as Core Programs. 

This idea was implemented during the past year. So 

far, this change has been quite successful. Researchers 

Beth Grafton-Cardwell and Joe Morse meet with the 

Pest Management Committee, and Mike Roose and Tracy 

Kahn meet with the New Varieties and Development 

Committee several times each year. These meetings occur 

both formally in a conference room and informally in research 

plots. 

MaryLou Polek 

In addition, Core Program scientists report to the industry 

in feature articles in the Citrograph magazine. This 

issue of Citrograph features the IPM program. The September/October 

issue will feature articles by Mike Roose, 

Tracy Kahn and Glenn Wright on breeding and evaluation 

of new varieties. 

Some of the advantages of this approach are that: 

• It allows for greater grower input into these programs 

• Growers get their questions answered more rapidly 

• Research is conducted using the varieties meaningful 

to the grower 

• Research is conducted on insect pests that are currently 

bothersome 

• It enables the industry and researchers to identify 

what problems are most important to growers 

We hope this creates an environment that encourages 

greater interaction and communication between the scientific 

community and the industry and promotes a greater 

dispersal of information to the entire industry. This is another 

way the Citrus Research Board ensures the maximum 

return on the investment of grower assessment dollars 

in research. 

Dr. MaryLou Polek is Vice President, Science & Technology, 

Citrus Research Board. 



INDUSTRY VIEWS 

Citrograph asks: “What are you doing to manage/reduce/ 

minimize insect pest resistance to insecticides” 

manage insect pest resistance by using the principles of resistance management 

that reduce the selective pressure to develop resistance in the target pest 

I 

population. Management tactics include avoiding unneeded treatments by using 

monitoring and economic thresholds to decide when a treatment is justified, 

rotating between pesticides with different modes of action, tank mixing materials 

to combine modes of action, using non-chemical tactics like cultural control, 

and maximizing biological control. My pest advisory work is in coastal citrus 

in the counties of Ventura, Santa Barbara and San Luis Obispo. In these areas, 

we are fortunate that the majority of our insect and mite pests are under fair 

to excellent biological control. Generally, we get by with one or two insect/mite 

sprays in a season. Citrus bud mite is the primary pest in the lemons, requiring 

at least annual treatment for economic control. Also, in some production areas, 

there is a complex of argentine ant provoked scales and mealybugs requiring 

a broad-spectrum material every two to four years. In my region, we do have 

an interesting case of treatment for one pest (citrus bud mite) leading to the 

development of resistance in another pest (citrus thrips). UC Riverside has 

documented resistance of citrus thrips in lemons to abamectin (Agri-Mek, etc.). 

Repeated annual or biannual treatment with oil plus abamectin for bud mite 

has given rise to citrus thrips resistant to abamectin. Fortunately, we have other 

selective thrips materials we can rotate to treat any problem thrips populations. 

And, the reliance on oil plus abamectin for bud mite control is waning as new 

materials with different modes of action become available for use in citrus to 

control bud mite. — Dave Machlitt, PCA and Certified Crop Advisor, Consulting 

Entomology Services 

I 

am the PCA and PCO for my family’s company, which has been in the pest 

control business since 1921. Cyanide fumigation and parathion were the main 

chemicals used in the early days of Integrated Pest Management. In the 1930’s, 

red spider mite was introduced in California and could not tolerate temperatures 

over 100 degrees, and the use of Morestan, Vendex, Omite and Plictran was 

needed as the only way to go forward in Riverside and San Bernardino counties 

in the field of Integrated Pest Management. The red spider mite eventually 

became resistant to these chemicals. The use of Sevin and Supracide was very 

harsh on the beneficials; however, Lorsban has been a very rewarding tool as its 

use has opened the door for many new chemicals. The introduction of Aphytis 

melinus in the 1930s was a slow but promising start as the temperatures in the 

Inland valleys are very good for Integrated Pest Management. The biggest test 

for our future will be trying to stay focused on Integrated Pest Management in 

the battle with the Asian citrus psyllid. Pyrethroids are a great control against 

the Asian citrus psyllid but can also disrupt the biological control provided by 

the beneficials. The use of neonicotinoids as a control system will probably be 

our best source as long as resistance doesn’t ruin them. Insects will always be a 

part of my history and future. — Alan A. Washburn, PCA and PCO, Washburn 

& Sons, Inc. 


have been dealing with this concern for quite a few years. When I first started 

I in this business (1960s), new insecticides were coming out quite regularly; 

most were in the organophosphate category. We soon learned that each year 

we would probably need a bigger/better “gun” for next year because of resistance. 

Over the years, I have always tried to minimize resistance by using the 

typical ways: alternating types of products and use only when necessary. This 

is not always successful; sometimes we can’t control a certain pest as well as 

we would like, and we find it necessary to repeat use or fall back to a more 

potent product. One of the concerns we face as pest control advisors is not 

only resistance but what a product might do to the ecological balance of a 

particular field. By using the proper choice of products that are now available, 

hopefully we can do both. Keeping in mind our primary role is to help keep 

the field as free of pests as possible and strive to maintain a balance and to 

minimize resistance at the same time. It’s not always easy. I have to say that it’s 

the challenge and rewards that make this something I enjoy doing. — Geary 

Austin, PCA, Leffingwell Ag Sales 

An invitation to the White House 

An opportunity for increased exports 

By Joel Nelsen 

Late last year, Sunkist’s Mike Wootton and I received 

the invitation to the White House as the President of 

South Korea was coming to town for the signing of the 

historic Korean Free Trade Agreement. Since it wasn’t 

for beers in the Rose Garden, we chose not to attend. 

On March 15 the Agreement was implemented, and 

while the vast majority of the work to achieve this agreement 

was conducted by Mike, it is the whole industry 

that could reap the benefit. It wasn’t too many years ago 

that Korea was a developing market with the vast majority 

of tonnage shipped graded as Choice. As the citizens 

of Korea and the retailers became more familiar with our 

California navel orange, their taste buds demanded more 

and better fruit. The industry responded, and today this 

market commands premium product and at a tonnage 

factor larger than any other export market. 

It’s the first trade agreement in years that will benefit 

the specialty crop industry and more specifically California 

citrus. For the past two decades, we have been on the 

losing end or just not included in trade agreements. And, 

for the past 20 years, the nation’s citrus imports have exploded 

while exports have increased very slightly and 

only because our marketers have been diligent in finding 

new business. 

This agreement, while not perfect, can be a boon 

for our sales. The obscene 54% tariff on oranges will be 

phased out on fruit arriving between March 1 and August 

31 with an immediate 20% reduction on landed fruit this 

year. For the next six years, the tariff will be phased out 

on all fruit landing in that time frame. 

For fruit landing the balance of the year, a tariff will 

remain at the higher level although each year 2,500 metric 

tons, increasing annually by 3%, will arrive duty-free. 

The current 30% tariff on lemons 

will be phased out over two years. 

The 30% duty on grapefruit will 

be phased out over five years. Not 

surprisingly, the mandarin variety 

is still stuck with a barrier as the 

144% duty will take 15 years to be 

eliminated. 

Bottom line is that the importer 

and retailer should pass this 

savings on to the Korean consumer, 

Mike Wootton 

thereby making the in-store California citrus that much 

cheaper. Ideally, this will trigger more purchases at store 

level and thus more growth for our exports in the future. 

Presently, California oranges are the largest agricultural 

export commodity from our state. With this agreement, 

our position can be strengthened. 

As for the beers, invite Mike over. The Bush Administration 

negotiators frustrated him by doing better on 

other commodities since there wasn’t a competitive concern. 

He’s earned a sip or two. l 


Proper monitoring and management 

of California Red Scale in 

the San Joaquin Valley 

Beth Grafton-Cardwell and Jim Stewart 

Editor’s Note: Work on California red 

scale is now a part of the CRB’s Core 

Program of Integrated Pest Management 

research with Drs. Grafton-Cardwell 

and Morse as lead investigators. 

California red scale has infested 

citrus nearly as long as citrus 

has been grown in California, 

but it did not become a significant pest 

of citrus in the San Joaquin Valley until 

the 1970s. 

All stages of California red scales 

attack twigs, leaves, and fruit by drinking 

plant fluids with their long, threadlike 

mouthparts. Heavily infested fruit 

may be downgraded in the packinghouse 

(Photo 1) and, if population levels 

are high, serious damage including 

leaf yellowing (Photo 2) and twig dieback 

reduces the health and vigor of 

trees. 

California red scale can be managed 

with releases of the parasitoid 

wasp Aphytis melinus (Photo 3), with 

oils, with the broad spectrum organophosphate 

insecticides chlorpyriphos 

(Lorsban) and methidathion (Supracide) 

and carbamates (Sevin), with 

soft insecticides such as oils, the insect 

growth regulators (IGRs) pyriproxyfen 

(Esteem) and buprofezin (Applaud) or 

with the foliar systemic lipid biosynthesis 

inhibitor spirotetramat (Movento). 

Sometimes, California red scale 

populations remain at low densities 

without any chemical intervention 

whatsoever and are managed by 

the naturally occurring parasitoids 

(Aphytis and Comperiella) and predators 

(Rhyzyobius beetles and lacewings). 

Sometimes they increase to 

high densities because of weather or 

chemical-related disruption of the natural 

enemies. Whatever the situation, 

management efforts should be aligned 

with careful monitoring of the scales 

to determine pest and natural enemy 

numbers. 

California red scale begins its life 

as a six-legged crawler that moves 

away from its mother towards the end 

of branches. It may crawl, or catch a 

ride on an insect, or blow in the wind. 

Once it settles down, if it is a female it 

does not move again. If it is a male, it 

does not move until it develops into a 

winged adult male. 

This scale biology (Photo 4) provides 

us with three potential populations 

to monitor: winged males, crawlers, 

and settled stages. This article will 

provide you with information as to 

how best to monitor those stages for 

the most effective California red scale 

management. 

Pheromone traps 

Male scales use the pheromones 

emitted by the 3rd instar female scales 

to find them for mating (Photo 5). Once 

mated, the female stops emitting pheromone. 

Males may crawl or fly to the 

females. A synthetic form of the female 

pheromone can be loaded onto rubber 

septa (Photo 6) and placed on a paper 

clip at the top of a sticky trap to attract 

the males, who then become stuck on 

the trap. Luckily for us, the males have 

a very characteristic brown bar on their 

backs that make them easy to separate 

from other small insects with the aid of 

a hand lens or microscope (Photo 7). 

Sometimes the densities of male 

scales on the traps become so numerous 

that it is very time consuming to 

count them. Dan Moreno, USDA en- 

Photo 1. Fruit may be lightly infested or 

heavily infested. Fruit with more than 10 

scales may be downgraded in the packinghouse 

because these patches of scale are 

noticeable. 


Photo 2. Leaves heavily infested 

with California red 

scales turn yellow around the 

scale bodies. 

Photo 3. The adult Aphytis wasp parasitoid 

of the California red scale. Photo by Beth 

Grafton-Cardwell.

tomologist, applied statistics to show 

that when densities are >200 scales per 

trap, you can count just the scales inside 

the square boxes on both sides of 

the card and, because those boxes represent 

20% of the surface area of the 

card, multiply by 5 to get an estimate of 

the total number of scales on the card 

(Photo 8A). 

When there are fewer than 200 

scales per card (Photo 9A-C), then it 

is more accurate to count scales on the 

entire card, not just inside the squares. 

When there are more than 2,000 

scales (Photo 8B-C), then you can just 

hold the card up to examples of various 

densities and use the photos to estimate 

what the density is. This greatly 

reduces the time spent counting scales. 

This method is much less accurate, especially 

since the two sides of the cards 

may vary a lot in their densities, but for 

cards above 2,000 scales it saves a lot 

of time. 

The Citrus Entomology Web site 

www.ucanr.org/sites/KACCitrusEntomology/ 

provides examples of various 

scale densities for comparison. 

California red scale completes three 

to four generations per year in the San 

Joaquin Valley. In this region, the harsh 

winters eliminate many of the younger 

stages of scales, so that the population 

consists primarily of late stage males 

and females at the end of winter. 

The first male flight occurs in 

March during which mating occurs. 

Approximately 550 degree-days later, 

the 1st generation of crawlers emerge 

from the female scale bodies. The exact 

timing of these events depends on temperature. 

California red scale begins to 

develop at temperatures above 53 o F. 

Degree-days for California red 

scale are defined as the accumulation 

of the average daily temperature (maximum 

temperature – minimum temperature 

divided by 2) above the threshold 

of 53 o F after the biofix of male flight. 

Biofix — A point in the lifecycle of 

an insect when a significant event 

occurs, that can be used as a starting 

point. For California red scale, 

the biofix of male flight is used as the 

starting point to accumulate degreedays 

in order to predict when crawlers 

will emerge. 

At 1,100 degree-days after the first 

male flight (or 550 degree-days after 

crawler emergence) another male flight 

Photo 4. The lifecycle of the California red scale (drawings by G. Conville). 

Photo 5. The male scale finds 3rd instar female scales and mates with them. 

Courtesy UC Statewide IPM Program. 

Photo 6. The pheromone trap for the 

California red scale consists of a white 

card, sticky on both sides, with a pheromone-impregnated 

lure above it. 

Photo 7. A close-up of the male of 

the California red scale showing the 

brown bar on its back that identifies 

it as a male scale. 


occurs, and so on (Figure 1). When 

temperatures are cool in the spring, it 

takes about eight weeks to accumulate 

550 degree-days (male flight to crawler 

emergence). When temperatures are 

hot in the summer, it only takes two to 

three weeks to accumulate 550 degreedays 

and events happen quickly. 

Pheromone traps are first placed 

in the orchards in late February-early 

March before the first male flight that 

occurs at about March 15. Use a minimum 

of two traps on a 5-acre block, 

four traps on a 10-acre block, six traps 

on a 20-acre block, and nine traps on a 

40-acre block. 

You want to have at least two traps 

per block, no matter how small the 

block, in case one gets lost or damaged. 

Hang the traps about eye level on a 

sturdy branch inside the NE corner of 

the tree canopy so that they are not 

disturbed. The pheromone lures are 

changed monthly from March through 

October. 

Weekly pheromone trap monitoring 

It is very important to choose a 

subset of your orchards and replace the 

pheromone trap cards weekly to obtain 

detailed information about when the 

male flights are occurring. Place these 

traps in a variety of orchards representing 

a range of temperatures (high 

ground and low ground, large orchards 

and small). At the Lindcove Research 

and Extension Center, we see about 7 

days difference in male flights between 

the high ground and low ground, even 

though these orchards are only a mile 

apart. 

For this type of pheromone trapping, 

use sites you don’t expect to 

treat with insecticides or that had high 

populations of scale the previous year 

to catch enough male scales in the first 

flight to be confident about the biofix. 

In these orchards, an additional 

monitoring tool is double sticky tape 

wrapped around a green-grey twig towards 

the end of the branch next to 

female scales (Photo 10). When the 

crawlers emerge and move towards the 

end of the branch, they become stuck 

on the tape. Checking these tapes each 

week provides added confirmation to 

the degree-day calculations that crawler 

emergence is taking place. 

Photo 8. Heavy densities of male scales on pheromone cards. From left to right: 

8,680 scales, 30,335 scales, and 70,845 scales per card. For these densities, 

count the scales inside the square boxes on both sides of the card and multiply 

times 5 to estimate their numbers or use reference cards. 

Photo 9. Light densities of male scales on pheromone cards. From left to right: 

230 scales, 730 scales, 2,445 scales. For cards with very low densities (less than 

200 scales), count all of the scales on both sides of the card to obtain an accurate 

estimate. For cards with moderate densities (200 to 2,000 scales), count 

the scales inside the square boxes on both sides of the card and multiply times 

5 to estimate their numbers. 

Pheromone trap monitoring by flight 

In the remaining orchards, use 

pheromone traps to determine areas of 

heavy scale infestation by leaving the 

traps out during the entire flight. 

• Hang the traps with a fresh 

lure just before the predicted 1st, 2nd, 

and 4th flights: the first flight is usually 

March 15, the second flight is 1,100 

degree-days after the biofix of the first 

male flight, and the fourth flight is 3,300 

degree-days after the biofix of the first 

male flight. 

• Remove traps at the end of each 

flight (your weekly pheromone cards 

indicate when flights are declining) and 

count (or estimate) scale numbers. 

• Record results. These traps will 

tell you which blocks and which areas 

of each block have treatable infestations. 

• Follow up with fruit evaluations 

and then decide on a treatment plan. 

In the San Joaquin Valley, citrus 

growers use pheromone traps to monitor 

male scales during the first (May), 

second (June-July), and fourth (Sep- 

Oct) flights. Degree-days are used to 

estimate when these flights are occurring. 

The best treatment results are obtained 

during the 1st or 2nd generation 

of scale crawler activity because the 

scale populations are highly synchronized, 

and pesticides generally work 

best on the younger instars of scales. 

However, when monitoring with pheromone 

traps, the 1st generation male 

flight is usually too low to detect more 

than a few scales (Figure 1) and so it is 


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not a good predictor of whether or not 

to treat; this flight is generally used just 

as a biofix. 

The 2nd generation flight can be a 

good indicator of heavy populations. 

The third flight is generally not used 

because the summer heat inhibits the 

flight. Most pest control advisors focus 

their monitoring efforts on the 4th 

flight, and if it is heavy (> 1,000/trap) 

and fruit is infested with scale at harvest, 

they plan to treat during the next 

season. 

The goal is to maintain California 

red scale populations at levels that do 

not result in more than 10 scale per 

fruit at harvest because these are the 

fruit that may be downgraded in the 

packinghouse. 

A chart was created in the 1980s 

that related the male scale trap card 

numbers in the 1st, 2nd and 4th flights 

to the expected percentage of scale infested 

fruit at harvest (Figure 2). We 

need to express caution when using the 

chart in Figure 2 because it was created 

by researchers during the organophosphate 

and carbamate insecticide era. 

Pheromone cards are not reliable 

predictors of scale populations 

in Aphytis-release orchards because 

Aphytis prefers to parasitize female 

scales, and the male scale numbers can 

be very high while the female population 

is very low. Pheromone cards also 

tend to overestimate populations that 

are treated by Movento, because Movento 

is controlling the scales on the 

fruit but not the wood. Thus, very high 

male scale counts can occur in spite of 

very clean fruit. 

In the other direction, pheromone 

cards may not be reliable predictors 

of red scale populations when insect 

growth regulators are used because the 

males are more sensitive to these insecticides 

than the females, and so the 

cards underestimate the scale population. 

In spite of these limitations, pheromone 

cards are very useful as one of 

several tools for monitoring California 

red scale. 

Examining fruit 

In all orchards, whether Aphytis 

wasps are released or trees are sprayed 

with insecticides, conduct visual inspections 

of citrus fruit on the trees once a 

month during August, September, and 

October. 

No. of Male scales/trap 

70000 

60000 

50000 

40000 

30000 

20000 

10000 

0 

1-Mar 

1-Apr 

3300 DD to 4 th male flight 

2750 DD to 3 rd crawlers 

2200 DD to 3 rd male flight 

1650 DD to 2 nd crawlers 

1100 DD to 2 rd male flight 

550 DD to 1 st crawlers 

1-May 

1-Jun 

1-Jul 

Walk around 20 trees in each quadrant 

of the block, and record the number 

of fruit examined, the number of 

fruit with scale, and the number of fruit 

with noticeable patches of scales (10 or 

more scales). Calculate the percentages 

of fruit with scale and more than 10 

scales. These fruit counts will give you 

an indication of whether treatments 

have been effective. 

Bin counts: At harvest, look at the 

fruit on the surface of at least 10 bins 

from areas throughout the block and 

count the number of uninfested and 

scale-infested fruit. Calculate the percentage 

of fruit with scale. At the same 

time, you can estimate the percentage 

of citrus thrips, katydid, cutworm, and 

peelminer-damaged fruit. 

Insecticide treatments 

Treatments with most insecticides 

are more effective if applied during the 

1st or 2nd generation of crawlers (early 

May, and late June to early July, respectively). 

This is because the stages of 

scale are synchronized by winter mortality 

of younger instars in these first 

two generations. Most pesticides are 

more effective against the younger in- 

Fig. 1. This figure shows a typical pattern of male scale flight activity (red line) and 

crawler emergence (green line) and the number of degree-days between the first 

flight and each generation. There are usually four flights and emergences in the 

San Joaquin Valley. Treatments target the first two crawler emergences because 

the population is more uniform and the scales have not yet reached the fruit. 

Photo 10. Double sticky tape wrapped around the green-grey wood branch of a 

tree near a female scale will collect the crawlers when they move toward the end 

of the branch. 

1-Aug 

1-Sep 

1-Oct 

1-Nov 

350 

300 

250 

200 

150 

100 

50 

0 

Crawlers per tape 


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Predicted Predicted fruit fruit infestation levels based on on California red red scale scale trap trap 

catches catches in in traps baited with pheromone in in the the San San Joaquin Joaquin Valley Valley 1 1 

Males/Trap 

First Flight 

(Apr/May) 

Males/Trap 

Second Flight 

(Jun/Jul) 

Males/Trap 

Fourth Flight 

(Sep/Oct) 

% Fruit with 

one or more 

scales 

% Fruit with 

11 or more 

scales 

0 1,783 2 0.7 

0 1,385 6,263 4 1.3 

21 3,006 10,893 6 2.0 

43 4,679 15,665 8 2.6 

65 6,403 20,594 10 3.3 

87 8,184 25,697 12 3.9 

111 10,028 30,993 14 4.6 

1 

From the Integrated Pest Management for Citrus, UC DANR Publication 3303. 

Fig. 2. The expected infestation of fruit at the end of the season based on pheromone 

trap counts in untreated orchards during the 1st, 2nd and 4th male flights. 

stars. During the first two generations, 

the crawlers emerge at about the same 

time, but as the season progresses to 

the 3rd and 4th generations, the crawler 

emergence overlaps with other stages. 

Be sure not to rely on only one 

chemical group, as this will eventually 

lead to resistance. 

Organophosphates and carbamates: 

Time organophosphate or carbamate 

insecticide sprays (Lorsban, 

Supracide or Sevin) to treat the crawler 

stage, after the peak in the 1st or 2nd 

male flight. Optimal treatment timing 

varies from year to year because of 

temperature but usually occurs in early 

May (first generation) or late June-early 

July (second generation). 

An even more reliable method of 

timing organophosphate or carbamate 

treatments is to monitor for crawlers 

by wrapping sticky tape around 1-yearold 

branches (about 0.5 inch diameter) 

that have both gray and green wood 

and are infested with live female scales. 

Replace the tapes weekly and so determine 

precisely when crawler emergence 

is occurring. 

The organophosphate and carbamate 

insecticides are the least selective 

insecticide choices, causing mortality 

of Aphytis for weeks to many months. 

There are numerous populations of 

California red scale that are resistant 

to organophosphate and carbamate 

insecticides because of decades of use, 

and in these cases treatment will only 

partially reduce the scale population. 

Insect growth regulators: Apply 

Esteem or Applaud sprays after crawlers 

have completely emerged and become 

white caps because these insect 

growth regulators kill the scale when it 

tries to molt to the next stage. 

Optimal timing for insect growth 

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egulators is the second generation of 

scale (June-July) in order to protect 

vedalia beetle during the time it is controlling 

cottony cushion scale (February-May). 

The insect growth regulators 

are safe for parasitic wasps, predatory 

mites, spiders, and lacewings but are 

quite toxic to vedalia beetles which are 

needed for cottony cushion scale control. 

Often they are used to reduce the 

pest population before Aphytis releases 

are initiated. 

Lipid synthesis inhibitors: Make a 

foliar application of Movento one to 

two weeks after the 1st, 2nd or 3rd male 

flights. The systemic action of Movento 

takes several weeks to move throughout 

the tree, so it needs to be applied 

A 

The heavier oils (435 to 455 distillation 

point) exert greater scale control than 

light oils (415 oil); however, they also 

have a greater potential for phytotoxicity. 

When using oils for scale control, 

make sure the orchard is well-irrigated 

and avoid treating during the heat of 

the day. In addition, treatments after 

October 1 carry some risk of increasing 

frost damage. Highly refined oils 

with the lowest sulfonated residues 

(unsulfonated residues >98%) have 

fewer problems with phytotoxicity. See 

UCIPM precautions for using petroleum 

oil sprays: http://www.ipm.ucdavis.edu/PMG/r107301011.html. 

Oil has the advantage of being less 

damaging to natural enemy populations 

than other insecticides because 

it only kills natural enemies that it 

contacts (brief persistence). It is best 

to avoid oil use in Aphytis release programs 

because oil treatments will eliminate 

the younger scale instars and thus 

synchronize development of the scale 

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Photos 11A and B. In August, fruit can 

be infested with scale in Aphytis release 

blocks and the scales appear healthy 

(A). However, in as little as one month 

later, the scales can begin to flake 

off of the fruit (B) because they have 

been parasitized, leaving behind white 

footprints that are easily washed off. 

earlier than the other insecticides. On 

the other hand, it is effective against all 

feeding scale stages (everything except 

late stage females and males), so precision 

of treatment timing is not as important 

as application technique. 

Make sure your orchard is well-irrigated, 

use 250-500 gpa water volume, 

and use an adjuvant such as oil. Movento 

is very safe for parasitic wasps and 

vedalia beetles, but it is toxic to predatory 

mites. 

Oils: Oils can be effective against 

California red scale if coverage is thorough 

and rates of 1.2-1.4% oil are used. 

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population. This makes parasitism by 

Aphytis more difficult because they 

prefer to deposit their eggs in 3rd instar 

scale; after an oil treatment, this stage 

may be absent for a period of time. 

Oil is an organically accepted treatment 

for California red scale. 

Parasite releases 

Releases of mass-reared Aphytis 

parasites can be useful in orchards with 

insufficient natural biological control. 

Keep in mind that pesticide residues 

on leaves may have a detrimental effect 

on released Aphytis parasites. Test 

for possible toxicity by putting 1-yearold 

twigs with leaves in gallon jars with 

Aphytis parasites for 24 hours and 

checking their mortality. If more than 

35% have died, residues are too high 

for Aphytis releases. Also, prepare a 

control jar filled with known untreated 

leaves for comparison of Aphytis vigor. 

In the San Joaquin Valley, recommended 

release rates are 100,000 parasites 

per acre per year for orchards undergoing 

the transition to an integrated 

pest management program. Begin releases 

about March 1, making releases 

of 5,000 parasites per acre every two 

weeks with the objective of releasing 

50% of the parasites during the critical 

spring period, 25% more in summer, 

and 25% more in fall. Continue releases 

through mid-November. 

A suggested release method is to 

hold the release cup upright and tap it 

to release a few Aphytis at every sixth 

tree in every sixth row, and start at 

different trees each time releases are 

made. This helps to spread the weakflying 

Aphytis through the block. Concentrate 

late season releases in areas 

in the block known to have higher red 

scale densities. Once an orchard has 

moved through the transition period (2 

to 4 years), the total number of parasites 

released per acre may be reduced 

to 50,000 to 70,000. 

Control ants – particularly the Argentine 

ant in Southern California and 

the native gray ant in the San Joaquin 

Valley – because they disrupt red scale 

parasites. Excessive dust that coats the 

leaves and fruit, including dust from 

manure mulches as well as whitewash 

and kaolin clays, interferes with parasitism 

and should be minimized or delayed 

until the end of the season when 

Aphytis has completed its work. Watering 

roads and washing trees can help 

solve these problems. 

Detailed evaluations of parasitism in 

Aphytis-release blocks 

In orchards where biological control 

agents such as Aphytis and Comperiella 

wasps are used to control scale, 

visually monitor all stages of scales on 

twigs, fruit, and leaves in August, September, 

and October. 

• Collect 10 scale-infested fruit 

(preferably from different areas of the 

block). Do not take more than one to 

two fruit per tree, avoiding trees in the 

outside rows. 

• Record the number of 2nd and 

3rd instar red scales and the number of 

these that are parasitized. To determine 

if a scale is parasitized, flip the cover 

over and search for Aphytis eggs, larvae, 

and pupae or Comperiella larvae 

and pupae (see publication “Life Stages 

of California Red Scale and its Parasitoids” 

http://anrcatalog.ucdavis.edu/ 

InsectMiteMolluscPests/21529.aspx for 

detailed photos). 

• Calculate the percentage parasitism 

by dividing the number parasitized 

by the total number of 2nd and 3rd in- 

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star scales examined. If biological control 

is functioning properly, you should 

see percent parasitism increase from 

just a few percent in August to more 

than 70% in October. You should also 

see dead parasitized scales flaking off of 

the fruit and leaving behind white “footprints” 

as the season progresses (Photos 

11A and B). 

Guidelines for determining when 

parasitism is at sufficient levels to fully 

control scale vary by growing region, 

cultivar, and whether or not fruit are 

sent to a packinghouse that employs a 

high pressure washer to remove scale. 

In the San Joaquin Valley, effective 

biological control of California red scale 

is achieved if by mid-to-late October 

more than 70% of the 3rd instar female 

scale are parasitized either by Aphytis or 

Comperiella. A good proportion (50%) 

of large 2nd instar females and 2nd instar 

males should also be parasitized. 

Summary 

California red scale can be effectively 

managed with Aphytis wasp releases 

or insecticide treatments or a combination 

of the two if you are careful about 

insecticide choice, rate, frequency of application, 

and treatment timing. Careful 

monitoring of California red scale populations 

using pheromone traps, crawler 

tapes and fruit inspection can greatly 

improve your decision making and provide 

more sustainable control of scales. 

Dr. Beth Grafton-Cardwell is a 

University of California Extension 

Specialist and Research Entomologist. 

She is a Citrus IPM Specialist in the 

Department of Entomology at UC Riverside 

and also serves as Director of the 

Lindcove Research and Extension Center. 

Jim Stewart is a partner in Ag IPM 

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Management of citrus thrips to 

reduce the evolution of resistance 

Joseph Morse and Beth Grafton-Cardwell 

Editor’s Note: Work on citrus thrips 

is now a part of the CRB’s Core Program 

of Integrated Pest Management 

research with Drs. Grafton-Cardwell 

and Morse as lead investigators. 

Background 

The citrus thrips, Scirtothrips citri 

(Moulton), is one of the few pests of 

California citrus which is native to California. 

In this case, the exotic organism 

is the citrus tree, and the native is citrus 

thrips. 

Dudley Moulton, a USDA scientist, 

named this insect in 1909 (calling it the 

orange thrips) after damage to citrus 

in southern Kern County made it clear 

that the characteristic surface scarring 

of citrus fruit that had been seen for 

many years was not wind rubbing or cold 

injury as had previously been thought. 

Even to the present day, it can be a 

challenge to differentiate citrus thrips 

damage from wind-caused fruit scarring. 

We like to use the presence of a partial 

or complete ring scar around the button 

as one good criterion – this is normally 

present with citrus thrips damage. In addition, 

checking fruit for damage shortly 

after petal fall will reveal the early stages 

of citrus thrips-induced fruit scarring. 

The article listed in “Further Reading”, 

Grafton-Cardwell et al. 2003, contains 

pictures that aid in differentiating 

citrus thrips fruit scarring from other 

types of fruit injury. 

The life cycle of citrus thrips 

Citrus thrips starts its life as an egg 

laid inside young leaves, twigs, flowers, 

or fruit. The most damaging stages are 

the first and second instar larvae (Figure 

1), because they prefer to hide under the 

button when the fruit is small, concentrating 

their feeding in that area, which 

causes the characteristic ring scar as the 

fruit expands. 

Mature second instar larvae crawl 

towards the inside, dark portions of the 


tree, looking for a place to hide, where 

they pass through two relatively inactive 

and non-feeding stages, the propupa 

and pupal stages. Typically, about onethird 

of the thrips pupate in cracks and 

crevices in the tree. and two-thirds drop 

to the soil to pupate in the upper layers 

of the leaf duff and soil beneath a tree. 

Fig. 1. It is the first and second instar 

(larger, above) citrus thrips that cause 

most fruit scarring. Photo by Jack Kelly 

Clark, courtesy UC Statewide IPM Program. 

Fig. 2. The predaceous mite Euseius 

tularensis will feed to some degree 

on citrus thrips (here feeding on a late 

second instar thrips). Photo by Jack 

Kelly Clark, courtesy UC Statewide IPM 

Program. 

The adults then emerge, mate, and 

produce the next generation of thrips. 

Adult females concentrate their feeding 

in one area to a lesser extent than 

larvae, and males don’t feed all that 

much or live very long -- thus they are 

not considered as damaging as the larvae 

in most situations. 

There are eight or more generations 

of citrus thrips attacking the leaves and 

fruit of citrus over the spring, summer, 

and fall. The first generation in the 

spring feeds on the leaf flush prior to 

bloom, and the second generation of 

larvae typically appears about the time 

of petal fall. It is the second and third 

generation of citrus thrips that normally 

are of economic concern. 

Small fruit are fairly susceptible to 

citrus thrips scarring, and as the fruit 

grows it becomes less susceptible. Once 

fruit are larger than about 1.5 inches in 

diameter, citrus thrips do not typically 

cause economic scarring because the 

fruit is tough enough to make extensive 

feeding difficult (thrips feed best on 

tender leaf and fruit tissue). 

Coastal lemons are an exception to 

the above scenario because multiple 

fruit sets are produced over the year. 

Rather than being a spring pest, citrus 

thrips on coastal lemons typically isn’t 

a concern until the mid-to-late summer 

fruit set. 

Natural enemies of citrus thrips 

We have searched for many years for 

ways in which to manage citrus thrips 

non-chemically and, in particular, with 

natural enemies. A number of natural 

enemies will feed on citrus thrips, but, 

unfortunately, in years when thrips levels 

are high they can cause substantial 

fruit injury in a relatively short period 

of time. Natural enemies often cannot 

keep up with the rapid growth of spring 

thrips populations. 

The only stages readily available 

for natural enemy attack are the first 

and second instar larvae. The two pupal

Thrips 

Leafminer 

Katydids 

Peelminer 

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stages are typically hidden in cracks 

or crevices in the tree or the soil, the 

winged adults are difficult for most 

predators to capture, and the egg stage is 

fairly protected inside plant tissue. Thus, 

any predator species trying to “make 

a living” off citrus thrips has sporadic 

availability of the larvae and cannot 

respond well numerically to increased 

thrips levels within a particular year. 

Triapitsyn & Morse (1999) searched 

for wasp parasitoids attacking citrus 

thrips and, although they found low 

levels of two parasitoid species on laurel 

sumac (a common native host, see 

below), these insects were not found 

associated with citrus. The citrus thrips 

has adapted over time to citrus, but 

perhaps the parasitoids have not, or they 

are not present at high enough levels to 

be detected easily. 

Jones & Morse (1995) used isoelectric 

gel electrophoresis to study 

to what degree the predaceous mite 

Euseius tularensis (Figure 2) feeds on 

citrus thrips, as this predator has been 

proposed as one of the more common 

natural enemies of citrus thrips on California 

citrus. Only 7 of 556 (1.3%) adult 

female E. tularensis tested positive for 

citrus thrips in their gut. Given this, we 

wonder if E. tularensis perhaps reduces 

citrus thrips levels only when the pest 

first starts to build from low levels but 

not when both species are present at 

moderate to high levels. 

Euseius spp. are generalist predators 

that feed on pollen, mites, insects 

and leaf sap, so they are not specifically 

tracking citrus thrips populations. Grafton-Cardwell 

demonstrated that pruning 

and fertilizing trees generated higher 

densities of Euseius than augmentative 

releases by providing the environment 

Euseius prefers. It is generally accepted 

that densities of >0.5 Euseius per leaf are 

associated with good citrus thrips control, 

but it is possible that the presence of 

this level of Euseius is indicative of good 

biological control in general because a 

suite of natural enemies provide citrus 

thrips suppression rather than Euseius 

specifically. 

Monitoring for citrus thrips 

Strategies used by pest control advisors 

and growers for managing citrus 

thrips vary. PCAs typically monitor 

citrus thrips levels on young, developing 

fruit immediately after petal fall to decide 

if treatments are needed. Post-petal 


Fig. 3. We rate navel orange scarring 

caused by citrus thrips on a 0-4 

scale where 0 = no scarring by citrus 

thrips (not shown), 1 and 2 are slight 

scarring (not sufficient to cause 

fruit to be downgraded from first to 

second grade) and 3 and 4 are severe 

(economic scarring). The threshold for 

fruit downgrading varies from year to 

year but is typically set at a level of 3 

scar or worse. 

fall treatments are not needed every 

year. This is because thrips levels vary 

from year to year, and also the timing of 

when the second and third generation of 

immature thrips appears in relation to 

fruit size varies. In the San Joaquin Valley, 

wet weather during bloom typically 

results in lower thrips levels after petal 

fall, in part due to greater mortality of 

the pupae in the soil. 

Careful monitoring can reveal orchards 

that have low levels of immature 

thrips on young fruit, and treatments 

can be delayed or eliminated altogether. 

Reducing the number of treatments will 

reduce the selection pressure for resistance 

to insecticides. Problems controlling 

citrus thrips in a particular grove are 

more likely if one or more treatments 

are used each year in contrast to a treatment 

perhaps being used only 5 years 

out of 10 years based on sampling for 

thrips severity each year. 

Insecticides can aggravate thrips 

populations 

Over the period 1972 – 2003, we ran 

citrus pesticide screening trials in Field 

12 (Atwood navel oranges) at the Lindcove 

Research and Extension Center 

(LREC). Untreated control plots were 

always included in order to assess how 

much fruit scarring would result if no 

treatment were applied. 

We used a 0-4 rating scale to assess 

the severity of citrus thrips-caused fruit 

scarring (see Figure 3), and scarring 

levels 3 and 4 were categorized as “economic 

scarring”. We set the threshold 

for economic scarring as the level that 

would typically lead to fruit being downgraded 

from first to second grade. 

Over the 20 years 1972-1991 (data 

prior to 1981 from O. L. Brawner and 

Dr. Bill Ewart), citrus thrips economic 

scarring on untreated trees ranged from 

1.2% (1986) to a maximum of 69.0% 

(1988) on outside lower fruit with a 

mean of 30.2% economic scarring. In 

contrast, over the 12 years 1992-2003, 

economic scarring ranged from 0.1% 

(2000) to a maximum of 10.7% (1997) 

with a mean of 4.4%. 

Clearly, something changed dramatically 

between these two time periods. 

The maximum level of severe scarring 

over the latter time period was about 

1/3 of the average level over the earlier 

period. We believe the reason for this 

is that citrus thrips is, to a considerable 

degree, a pesticide-induced pest.


During the first time period, 1972- 

1991, broad-spectrum organophosphate, 

carbamate, and pyrethroid insecticides 

were used in the SJV and in the test 

areas of this field at Lindcove for citrus 

thrips control. Many pest control advisors 

mentioned to us that spraying thrips 

“only makes them mad”. They found 

that if the first spray did not control 

them well, they “came back” at very high 

levels and were more difficult to control. 

We believe that what was happening 

was that citrus thrips populations 

had developed resistance in some areas 

and to varying degrees to organophosphates, 

carbamates, and/or pyrethroids. 

The level of resistance varied greatly 

depending on how often and which 

chemicals had been used in the past and 

how long thrips had NOT been exposed 

to that chemistry so that resistance 

could revert. 

When citrus thrips are sprayed with 

a broad-spectrum insecticide (as is the 

case for most products in these three 

classes of chemistry, see Table 1) these 

sprays reduce most natural enemies that 

might help hold the thrips in check. If 

the thrips are somewhat resistant, they 

are not completely killed. 

Hormoligosis is the term used to 

describe the stimulation of insects or 

mites when they are exposed to sublethal 

rates of pesticides or other toxins. 

As pesticide residues drop to sub-lethal 

rates, citrus thrips can be stimulated 

(depending on pesticide and dose) to 

lay more eggs, contributing to a “resurgence” 

of the thrips population several 

weeks later. 

Hormoligosis — the stimulation of insects 

or mites when they are exposed 

to sub-lethal rates of pesticides or 

other toxins. 

What happened to contribute to 

lower thrips levels over 1992-2003 The 

relatively “soft” insecticides Agri-Mek 

and Success (Entrust is the organic version) 

were registered for use on California 

citrus in 1994 and 1998, respectively, 

and growers largely switched to using 

those products, especially Success, for 

citrus thrips control (see Figure 4). In 

addition, growers switched to Esteem 

or Applaud for red scale control, in both 

cases replacing broad-spectrum organophosphate, 

carbamate, and pyrethroid 

treatments with softer insecticides 

that allowed more natural enemies to 

survive. 

Thus, although citrus thrips can still 

cause economic damage when weather 

conditions are conducive, in general, 

citrus thrips is less of a problem than it 

used to be. Whereas citrus thrips insecticide 

screening trials at LREC were 

quite productive prior to 2003, once the 

“organophosphate era” ended, it was 

difficult to consistently see differences 

between fruit scarring on trees treated 

with the standard, effective product 

versus levels on untreated control trees. 

We shifted in 2004 to screening 

experimental pesticides on what we 

believe is one of the major natural hosts 

of citrus thrips in California (before 

citrus was introduced), laurel sumac, 

in greenhouse trials (see Morse 1995). 

Treatments on non-bearing citrus 

Some growers and PCAs believe 

that treating citrus thrips on non-bear- 

Table 1. Pesticides that might be used in rotation for citrus thrips control. 

Trade name Common name Pesticide class Mode of Action a Critical as part Resistance situation with Comments and application 

of future ACP citrus thrips methods to improve efficacy 

control 

Dimethoate (and Dimethoate Organophosphate 1B Yes Resistance in some areas Moderately systemic material 

generics) 

depending on the degree of 

past organophosphate use 

Carzol Formetanate Carbamate 1A No Resistance in some areas 

hydrochloride 

depending on the degree of 

past carbamate use 

Veratran D Sabadilla alkaloids Botanical unclassified No Resistance not yet seen Adding 1-2 gallons of 

with citrus thrips (seen with molasses/acre assists with 

avocado thrips) 

efficacy and persistence; 

Critical to reduce spray tank 

pH to 4.5 prior to adding 

material; Works poorly in 

cold weather (active only as 

a stomach poison) 

Baythroid XL Beta-cyfluthrin Pyrethroid 3A Yes Resistance in some areas 

Danitol Fenpropathrin depending on the degree of 

Mustang Zeta-cypermethrin past pyrethroid use 

Agri-Mek (and Abamectin Chloride channel 6 Somewhat Possible cross-resistance Translaminar, add oil (1/4% 

generics) activator (adults) with class 5 or more) to aid leaf 

penetration and persistence 

Success Spinosad Spinosyn 5 Delegate – Possible cross-resistance Translaminar, add oil (1/4% 

Entrust Spinosad (organic) Yes with class 6 or more) to aid leaf 

Delegate Spinetoram penetration and persistence 

Movento Spirotetramat Inhibitor of acetyl 23 Yes Resistance management Highly systemic; add oil to 

CoA carboxylase critical to protect this improve leaf penetration 

material’s efficacy for ACP, (surface residues are NOT 

red scale, and citrus thrips active) 

control 

a 

The IRAC MoA (mode of action) for each class of chemistry (see www.irac-online.org). 


ing, young citrus has value in terms of 

enhancing tree growth and/or bringing 

the tree into production sooner. We 

suggest it is perhaps worthwhile treating 

for citrus thrips only in year 1, when the 

trees are first planted in the ground to 

ensure they get a good start. 

For older trees, we admit that the 

leaf scarring of young leaves by citrus 

thrips is unsightly (Figure 5), but does 

citrus thrips really slow the growth of 

young trees, if they are well irrigated, 

well watered, and otherwise healthy 

We believe the answer to that is no, 

based on two research trials reported 

in Grafton-Cardwell et al. (1997) in the 

San Joaquin Valley. 

The first study was done on navel 

oranges at LREC using 50 single-tree 

replicates over a three-year period. 

Treatment 1 never received any pesticides, 

and treatments 2-6 received 2 

summer treatments in year 1. In years 

2 and 3, the treatments were: (2) no 

citrus thrips treatments; (3) 2-3 spring 

treatments/year; (4) 1 fall treatment/ 

year; (5) 2-3 spring and 1 fall treatment 

each year; and (6) 2-3 spring, 4 summer, 

and 1 fall treatment each year. Thus, 

trees received as many as 17 treatments 

over a three-year period. As an indication 

of tree growth, we measured trunk 

circumference at 4 cm above the bud 

union 1, 2, 3, and 4 years after the trees 

were planted. 

To summarize the results, none of the 

6 treatments had a differential impact on 

tree growth; that is, we could detect no 

difference in tree size during years 1-3 

whether they were untreated, treated 

with 17 treatments, or with an intermediate 

number of treatments. The only 

significant effect we measured was a loss 

in citrus thrips susceptibility to Carzol. 

The second study was done with 

commercial Valencia oranges planted 

in April in Fresno County over a threeyear 

period. A 20-acre block was divided 

into 18 plots of 180-200 trees each, and 

9 plots were randomly assigned to be 

treated with (1) no citrus thrips treatment 

over years 1-3 or (2) grower choice 

of treatments including a range of insecticides 

used for citrus thrips control 

(7 treatments in year 1, 7 in year 2, 5 

in year 3). The entire field was treated 

after petal fall in the spring of year 4 to 

protect fruit from citrus thrips scarring. 

Again, we measured trunk diameter 

in years 1-4 and saw no difference between 

0 treatments and, in this case, 19 

treatments over years 1-3. In this study, 

we also measured fruit production in 

year 3. Although we saw a slight numerical 

trend with somewhat more fruit in 

the treated plots, this difference was not 

statistically significant. By year 4, this 

slight numerical trend had disappeared 

(an average of 244.5 fruit per tree on 

treated trees, 249.0 on untreated trees). 

Our conclusion for both the navel 

and Valencia studies is that despite leaf 

scarring caused by citrus thrips being 

unsightly, treating young citrus very 

much, if at all, is likely wasting money 

and can significantly contribute to the 

Acres Treated 

Insecticides Used for Citrus Thrips & Katydid Control 

in the San Joaquin Valley 

450,000 

400,000 

350,000 

300,000 

250,000 

200,000 

150,000 

100,000 

50,000 

0 

1991 

1993 

1995 

1997 

Cygon Carzol Baythroid Baythroid XL Danitol 

Agri-Mek Veratran Success Delegate 

evolution of pesticide resistance. 

We strongly suggest that growers 

not treat citrus thrips on non-bearing 

citrus except perhaps the first year when 

trees are very small. The cost, in terms 

of losing the efficacy of pesticides to 

resistance, is too high and this is going 

to be even more important once treatments 

are needed for Asian citrus psyllid 

(ACP) control. 

The history of citrus thrips pesticide 

resistance 

Table 2 shows that over the years, 

citrus thrips has evolved pesticide resis- 

Fig. 4. Damage of young flush on citrus can be unsightly but does not warrant 

treatment except perhaps on very young trees just after planting. Photo by Jack 

Kelly Clark, courtesy UC Statewide IPM Program. 

Fig. 5. Insecticide acreage treated with various insecticides for citrus thrips 

and katydid control demonstrating the changes in grower uses during 1991- 

2010 for the San Joaquin Valley. Totals for Cygon and Agri-Mek include generic 

formulations of the same chemical. 

1999 

2001 

2003 

2005 

2007 

2009 


tance to a number of different pesticides 

from DDT to pyrethroids in as short a 

time as 1 year (to Dieldrin after resistance 

to the related DDT had appeared) 

and in as many as 18 years (dimethoate). 

We now have evidence for resistance to 

Delegate in a population of citrus thrips 

in the San Joaquin Valley. 

Citrus thrips’ ability to rapidly develop 

resistance concerns us each time 

growers consistently rely on one or a 

small number of insecticides for the control 

of a particular pest (citrus thrips, red 

scale, ACP, etc.). Unfortunately, we often 

do not have as many effective pesticides 

from different classes of chemistry available 

for rotation as is desirable. 

What is meant by the word “resistance” 

There are a number of 

definitions, but we like two of the more 

common ones: (1) if the “resistant” 

population of insect or mite develops 

a >10-fold increase in the LC 50 

or LC 90 

(the pesticide concentrations needed to 

kill 50 or 90% of the population, respectively) 

or (2) if one sees clear evidence 

of a lack of field control (either complete 

failure or reduced persistence) when the 

material is used properly. 

The first definition recognizes that 

there is variability in the response of 

various insects and mites to pesticides, 

and a population has not developed 

resistance until at least a 10-fold level 

has been reached. The latter definition 

is more of an operational term – when 

the material stops working or works 

less well, resistance has occurred. In 

most cases, laboratory measurements 

and field experience correlate well. 

Researchers typically try to take 

baseline resistance data in the labora- 

tory before a pesticide is used widely 

so they can later watch for changes 

in responses to the insecticide and 

confirm those changes based on field 

observations. 

Sometimes resistance to one insecticide 

also confers resistance to 

another insecticide. This is known as 

“cross resistance”. One way that insects 

resist pesticides is by breaking down 

(metabolizing) the pesticide more 

quickly; this is called metabolic resistance. 

Citrus thrips that have evolved 

resistance to organophosphates have 

increased levels of enzymes that break 

down the organophosphate relatively 

quickly compared to susceptible strains, 

and this also gives them resistance to 

other organophosphate and carbamate 

insecticides (MoA category 1, Table 1). 

A second type of resistance is due to 

an altered target site for the pesticide. 

The rapid development of citrus thrips 

resistance to pyrethroids may be due 

to previous exposure to DDT because 

these two types of pesticides have similar 

target sites (MoA 3). 

Following the registration of Success 

(spinosad) for use on California citrus in 

1998, Success and Entrust were widely 

used for citrus thrips control, accounting 

for an average of 43% of the spring 

thrips/katydid treatments in the San 

Joaquin Valley between 1999 and 2007 

(Figure 4). 

Delegate (spinetoram) was registered 

in 2007, is in the same class of 

chemistry as Success (cross resistance 

is expected), and is somewhat more 

effective and persistent against citrus 

thrips than Success. The use of Delegate 

until recently was hampered by the lack 

of MRLs (maximum residue limits) by 

some of the foreign trading partners to 

which California citrus is shipped. Each 

year over the last six years or so, we have 

offered to test for citrus thrips susceptibility 

to either Success or Delegate 

based on baseline data we took before 

these products were widely used. 

Each year, we have been pleasantly 

surprised to see a lack of documentable 

resistance. However, following a report 

of poor citrus thrips control from a 

Delegate application during the spring 

of 2011, we measured a significant increase 

in the spinetoram LC 50 

for citrus 

thrips collected at this location (9.4 

to 19.8-fold higher LC 50 

than baseline 

values determined in 2008). Actually, 

we should feel very fortunate that it has 

been 14 years before the first signs of 

field resistance were observed with the 

Success/Delegate chemistry in the San 

Joaquin Valley. 

The need to manage citrus thrips 

resistance 

We plan to continue to monitor the 

Delegate resistance situation to determine 

whether this is a fairly isolated 

incident and whether such resistance is 

developing in other areas of the SJV. In 

addition, we are accelerating the testing 

of new products and chemistries which 

might be used to help manage citrus 

thrips resistance (several are moving 

closer to registration). 

As mentioned by Morse & Grafton- 

Cardwell (2009), once Asian citrus 

psyllid enters the SJV, it will be even 

more important to manage pesticide 

resistance by rotating between products 

with different modes of action, as many 

Table 2. Partial history of citrus thrips pesticide resistance evolution in California. 

Pesticide common Class of chemistry Mode of Action a Year first used Year first field 

name commercially failure reported Reference 

DDT Sodium channel modulator 3 1946 1949 Morse & Brawner 1986 

Sabadilla + sugar Botanical bait unclassified 1948 -- Morse & Brawner 1986 

Dieldrin GABA-gated chloride channel antagonist 2A 1953 1954 Morse & Brawner 1986 

Malathion Organophosphate 1A 1954 1961 Morse & Brawner 1986 

Dimethoate Organophosphate 1A 1962 b 1980 Morse & Brawner 1986 

Carzol Carbamate 1B early 1980s 1986 Immaraju et al. 1989 

Baythroid Pyrethroid 3 1991 1996 Morse & Grafton-Cardwell 2009 

Abamectin Macrocyclic lactone 6 1994 -- -- 

Success + oil Spinosyn 5 1998 -- -- 

Delegate + oil Spinosyn 5 2007 2011 Morse et al. unpublished 

Movento + oil Acetyl CoA carboxylase inhibitor 23 2008 -- 

a 

The IRAC MoA (mode of action) for each class of chemistry is listed (see www.irac-online.org). Cross-resistance is expected between chemicals with the same mode of action. 

b 

Non-bearing (limited) use only, until 1969. 


of the materials that are effective against 

citrus thrips also will assist in control of 

ACP (see Table 1). There are currently 

six modes of action (1, 3, 5, 6, 23, and 

unclassified) for insecticides registered 

for citrus thrips control (Table 1). 

The best advice regarding resistance 

management for citrus thrips, or most 

pests for that matter, is to: (1) minimize 

pesticide use to the extent that is possible 

by sampling carefully to make sure 

the treatment is needed; (2) maximize 

the use of non-chemical control methods; 

(3) rotate among effective available 

chemistries to the maximum extent 

possible (clearly understand what mode 

of action each pesticide has and where 

the potential for cross resistance exists); 

and, (4) when a treatment is needed, 

apply it at the optimal time and with 

the best possible application method 

so as to avoid the need for re-treatment 

(Table 1). 

We view the first observation of 

citrus thrips resistance to Delegate in 

2011 as an early warning. To maintain 

the effectiveness of Delegate and Success 

against citrus thrips, avoid making 

more than one application of a Group 

5 insecticide (Delegate, Success, or 

Entrust) to a block each year. If additional 

applications are needed, other 

effective insecticides with different 

modes of action should be used. Also, 

try to make applications to adjacent 

blocks or groves at the same time or 

within a few days of each other to have 

an “area-wide” impact and thus slow 

re-infestation. 

It is important that we hold this 

situation in check as best we can until 

new chemistries become available for 

citrus thrips control. It is hoped we will 

have at least one new chemistry to use 

against citrus thrips prior to the 2013 

spring field season. 

Acknowledgements 

We would like to thank the Citrus 

Research Board for funding to support 

in part the research described herein. We 

also thank Alan Urena, Lindsay Robinson, 

Pamela Watkins, and Heavenly 

Clegg for technical support and past 

graduate students/postdoctoral scientists 

Tim Grout, Bill Wiesenborn, Alex 

Rhodes, John Immaraju, Nasser Zareh, 

Jim Ferrari, Steven Jones, Heinrich Schweizer, 

Inamullah Khan, Kris Tollerup, 

and Dr. Serguei Triapitsyn for contributing 

to past citrus thrips research efforts 

which lead to some of the information in 

this article. Photographs 1, 2, and 4 were 

provided by Jack Kelly Clark, courtesy 

of the UC Statewide IPM Program and 

are copyrighted by the Regents of the 

University of California. 

Dr. Joseph G. Morse is a Professor 

of Entomology and Dr. Beth Grafton- 

Cardwell is an Extension Specialist and 

Research Entomologist. Both are members 

of the Department of Entomology, 

University of California Riverside. 

Further reading 

Grafton-Cardwell, E.E., J.G. Morse, 

and A. Gjerde. 1997. Effect of Insecticide 

Treatments to Reduce Infestation by 

Citrus Thrips (Thysanoptera: Thripidae) 

on Growth of Nonbearing Citrus. 

Journal of Economic Entomology 91(1): 

235-242. 

Grafton-Cardwell, E.E., N.V. 

O’Connell, C.E. Kallsen, and J.G. Morse. 

2003. Photographic Guide to Citrus 

Fruit Scarring. University of California 

Division of Agriculture and Natural 

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trademarks of Nichino America, Inc. Farm Safely. Always read and follow label 

directions. 888-740-7700 www.nichino.net 

Resources Publication 8090, Oakland, 

CA. 8 pp. 

Haviland, D.R., S.M. Rill, and J.G. 

Morse. 2009. Southern Highbush Blueberries 

Are a New Host for Scirtothrips 

citri (Thysanoptera: Thripidae) in 

California. Florida Entomologist 92(1): 

147-149. 

Jones, S.A. and J.G. Morse. 1995. Use 

of Isoelectric Focusing Electrophoresis 

to Evaluate Citrus Thrips (Thysanoptera: 

Thripidae) Predation by Euseius tularensis 

(Acari: Phytoseiidae). Environmental 

Entomology 24(5): 1040-1051. 

Immaraju, J.A., J.G. Morse, and D.J. 

Kersten. 1989. Citrus Thrips (Thysanoptera: 

Thripidae) Pesticide Resistance in 

the Coachella and San Joaquin Valleys 

of California. Journal of Economic Entomology 

82(2): 374-380. 

Immaraju, J.A., J.G. Morse, and R.F. 

Hobza. 1989. Field Evaluation of Insecticide 

Rotation and Mixtures as Strategies 

for Citrus Thrips (Thysanoptera: 

Thripidae) Resistance Management in 

California. Journal of Economic Entomology 

83(2): 306-314. 

Lovatt, C.J., S.M. Streeter, T.C. 

Minter, N.V. O’Connell, D.L. Flaherty, 

M.W. Freeman, and P.B. Goodell. 1984. 

Phenology of Flowering in Citrus sinensis 

(L.) Osbectk, cv. Washington navel 

orange. Proceedings of the International 

Society of Citriculture 1: 186-190. 

McMurtry, J.A. and B.A. Croft. 1997. 

Life-styles of Phytoseiid Mites and Their 

Roles in Biological Control. Annual Review 

of Entomology 42: 291-321. 

Morse, J.G. 1995. Prospects for IPM 

of Citrus Thrips in California. Pp. 371- 

379, In: Thrips Biology and Management. 

Proceedings, 1993 International 

Conference on Thysanoptera, Towards 

Understanding Thrips Management. 

Editors: B.L. Parker, M. Skinner, T. 

Lewis. Sept. 28-30, 1993, Burlington, VT. 

Plenum, New York, NY. 636 pp. 

Morse, J.G. and O.L. Brawner. 1986. 

Toxicity of Pesticides to Scirtothrips citri 

(Thysanoptera: Thripidae) and Implications 

to Resistance Management. Journal 

of Economic Entomology 79(3): 565-570. 

Morse, J.G. and H. Schweizer. 1996. 

Citrus Thrips Resistance — A Problem 

Requiring Grower and PCA Restraint. 

Citrograph 81: 11-15. 

Morse, J.G. and E.E. Grafton- 

Cardwell. 2006. Bear Citrus Thrips 

Resistance in Mind When Deciding 

Whether and How to Treat in 2006. Topics 

in Subtropics 4: 11-13. 

Morse, J.G. and N. Zareh. 1991. 

Pesticide-Induced Hormoligosis of Citrus 

Thrips (Thysanoptera: Thripidae) 

Fecundity. Journal of Economic Entomology 

84(4): 1169-1174. 

Morse, J.G. and E.E. Grafton- 

Cardwell. 2009. Managing Insecticide 

Resistance will be Key to the Future 

of Effective Citrus Pest Management. 

Topics in Subtropics 7(1): 6-8. 

Morse, J.G., E.E. Grafton-Cardwell, 

and A.A. Urena. 2001. Management Options 

for Citrus Thrips in the San Joaquin 

Valley. Citrograph 86: 4-5, 12. 

Rhodes, A.A., J.G. Morse, and C.A. 

Robertson. 1989. A Simple Multigeneration 

Phenology Model: Application to 

Scirtothrips citri (Thysanoptera: Thripidae) 

Prediction on California Oranges. 

Agriculture, Ecosystems and Environment 

25(4): 299-313. 

Triapitsyn, S.V. and J.G. Morse. 1999. 

Survey of Parasitoids of Citrus Thrips, 

Scirtothrips citri (Moulton, 1909), in 

Southern California. Russian Entomology 

Journal 8(1): 47-50.l 



The evolution of biologically-based 

Integrated Pest Management in California citrus: 

history and perspective 

Joseph Morse and Beth Grafton-Cardwell 

Citrus production in California occurs in four major 

climatic growing regions. These include coastalintermediate 

Southern California, interior Southern 

California, the Southern California desert valleys, and the San 

Joaquin Valley (Figure 1). 

Historically, the Southern California growing regions 

dominated in acreage, but over the past 50 years or so urban 

pressures, including rising land values and water costs, have led 

to a shift in acreage. Currently, more than 75% of the state’s 

citrus acreage is located in the San Joaquin Valley. 

Each of the climatic regions has somewhat different 

weather, key pest problems, levels of endemic biological 

control, and levels of adoption of biologically-based citrus 

IPM practices. 

The fumigation era 

The history of citrus arthropod pest management in California 

may be divided into three major eras, each of them 

broadly overlapping in time and showing regional differences. 

The first of these, prior to the introduction of DDT insecticide 

in 1946, might be called the “fumigation era.” During 

this period, beginning with the introduction of hydro-cyanic 

acid (HCN) in 1886 in California, all non-fumigant pesticides 

available (Paris Green, lead and calcium arsenate, oil, sulfur, 

lime sulfur, nicotine, rotenone, pyrethrum, etc.) had limited 

efficacy by modern standards. At peak use of HCN on citrus in 

California (1930-1940), as much as 6 million pounds of liquid 

HCN was used in a single season. 

This era was also characterized by numerous examples of 

rather high quality observational research focused on various 

aspects of taxonomy, basic biology, and the ecology of citrus 

pests. In addition, classical biological control (returning to 

the area of origin to search for and import natural enemies 

that co-evolved with the target pest) solved a number of pest 

outbreaks caused by the introduction of exotic citrus pests 

into California from various regions of the world. 

The science and philosophy of classical biological control 

originated with the outstanding control of cottony cushion 

Photo 1. Vedalia beetle adult, 

eggs, and larva feeding on 

cottony cushion scale. 

Photo by Jack Kelly 

Clark, courtesy UC 

Statewide IPM 

Program. 

San Joaquin Valley Navels, 

Valencias & Mandarins 

Coastal 

Lemons 

Fig. 1. Major growing regions for 

citrus in California. 

Southern Interior 

Navels & Valencias 

Desert 

Grapefruit 

Photo 2. California red scale infested orange. 

Photo by Beth Grafton-Cardwell. 


Photo 3. First and second instar citrus thrips 

are the stages that damage fruit. Photo by 

Jack Kelly Clark, courtesy UC Statewide IPM 

Program. 

Photo 4. Aphytis melinus wasps parasitizing 

California red scale. Photo by Jack Kelly 

Clark, courtesy UC Statewide IPM Program. 

scale achieved by introducing the vedalia beetle (Photo 1) 

and Cryptochaetum fly into Southern California citrus groves 

in 1888. This led, in part, to the establishment of strong research 

units emphasizing biological control of pests of citrus 

and other crops at both Berkeley and Riverside within the 

University of California system. 

The pesticide era 

The second era in the history of citrus pest management in 

California, ranging from perhaps 1946 to the mid 1970s, might 

be called the “pesticide era” following the introduction of 

DDT and other organochlorines, and later, organophosphate 

and carbamate insecticides. 

DDT was experimentally tested on citrus against California 

red scale (Aonidiella aurantii) (Photo 2) in 1943, was 

released for commercial use in the U.S. in 1945, and was first 

used commercially on California citrus in 1946. 

Throughout the U.S., the unprecedented level of control 

achieved with DDT on a wide range of pest species initiated, 

in retrospect, a shift of entomological research from a focus 

on basic pest biology to an emphasis on various aspects of 

chemical control. As an index of this shift, the percentage 

of research papers published in the Journal of Economic 

Entomology on the general biology of insect pests and their 

biological control dropped from 33% in 1937 to 17% in 1947, 

while the percentage devoted to the testing of insecticides 

rose from 59% to 76%. 

More so than with other commodities, however, research 

on basic pest biology, and especially biological control, continued 

on citrus in California during the pesticide era, due in 

large part to the presence and citrus focus of an independent 

Department of Biological Control at the University of California, 

Riverside and Berkeley campuses (at the time, this 

was a single department). 

Although we use the date of the introduction of DDT on 

citrus in California in 1946 as the start of the pesticide era, 

DDT use on citrus in the state had a limited lifespan. One 

of its main uses was for control of citrus thrips (Scirtothrips 

citri) (Photo 3), but resistance to DDT appeared in this species 

in 1949 (and is still present), resulting in reduced use in 

the following years. 

The philosophical bias in favor of chemical control of citrus 

pests maintained its momentum in California, however, with 

the commercial introduction of parathion in 1949, dieldrin 

in 1953, and malathion in 1954. Since that time, a number of 

other organophosphate and later, carbamate insecticides, were 

introduced and relied upon by growers. 

Biologically-based IPM 

The third era, which we might call the “biologically-based 

integrated pest management era” has a less discrete beginning 

on citrus in California and continues to evolve to the 

present day. 

Here we define the biologically-based IPM approach 

as the combined use of selective chemical, biological, and 

cultural controls. The biologically-based approach includes 

regular monitoring of pest and natural enemy species, augmentative 

release of biological control agents such as Aphytis 

melinus (Photo 4) for control of California red scale, and use 

of economic thresholds which limit pesticide applications to 

an “as-needed basis”. The choice of selective pesticides and 

the timing and method of their application is made in a way 

that minimally interferes with endemic and augmentatively 

released natural enemies. 

Biologically-based IPM emphasizes the use of biological 

control and minimizes the use of pesticides that would 

be harmful to natural enemies. This is done by the careful 

selection of which pesticides are used and/or when and 

how they are applied. It requires the input of a supportive 

grower and a knowledgeable pest control advisor who 

carefully tracks pest and natural enemy populations. Such 

a system must be responsive to the appearance of new pest 

species and the year-to-year variability in pest and natural 

enemy populations. 

Origins of biologically-based citrus IPM in California 

A major tenet of biologically-based citrus IPM is a recognition 

of the importance of maintaining endemic (natural) 

biological control through minimal use of broad-spectrum 

pesticides, minimization of dust caused by vehicular traffic, and 

suppression of ant species which interfere with natural enemies. 


In California, the appreciation for biological control was 

stimulated, in part, by classical biological control successes on 

citrus in Southern California. Following the example of cottony 

cushion scale, as new citrus pest species were introduced 

into the state, foreign exploration programs were initiated with 

the aim of introducing effective natural enemies of these pests. 

Many of these programs were initially unsuccessful but 

eventually led to control of the target or other non-target 

pests through the accumulation of a complex of natural enemy 

species or the introduction of a key natural enemy species. 

In Southern California, 13 exotic pests have been controlled 

biologically. Successes include the complete control 

of citricola scale (Coccus pseudomagnoliarum) in Southern 

California, where it is almost never seen presumably due to 

natural enemies introduced to control black scale (Saissettia 

oleae). 

Other classical biological control successes include control 

of purple scale (Lepidosaphes beckii), Comstock mealybug 

(Pseudococcus comstocki), citrophilus mealybug (P. calceolariae), 

longtailed mealybug (P. longispinus), citrus mealybug 

(Leptomastidae abnormalis), Japanese bayberry whitefly 

(Parabemesia myricae), citrus whitefly (Dialeurodes citri), and 

cloudy-winged whitefly (D. citrifolii). 

Many other arthropod pests of citrus in California are 

partially controlled in one or more of the growing regions in 

California by introduced or endemic natural enemies. 

In addition to classical biological control, the practice of 

augmentatively releasing biological control agents has a long 

and successful history on California citrus. The Fillmore Citrus 

Protective District (FCPD) was established in 1922 in coastal 

Southern California, mainly as a grower cooperative to assist 

with control of California red scale. In 1926, citrophilus mealybug, 

first introduced into the state in 1913, became a serious 

problem for FCPD growers and led to the construction of 

an insectary for rearing and annual release of the mealybug 

destroyer (Cryptolaemus montrouzieri). 

In 1937, the FCPD insectary began rearing and releasing 

Metaphycus helvolus (Photo 5) for black scale control and, in 

1960, Aphytis melinus rearing began for control of California 

red scale in grower-member groves. Unfortunately, a declining 

Valencia orange market and conversion of groves to other 

uses resulted in closure of the FCPD and its insectary in 2003. 

Augmentative biological control is the practice of rearing 

and releasing large numbers of a natural enemy species 

to “augment” the impact of other natural enemies that are 

present. In the San Joaquin Valley, predators and parasitoids 

attack California red scale but without augmentation, their 

impact is usually insufficient to maintain red scale below 

economic levels. 

During the pesticide era, growers and pest control advisors 

in coastal and interior citrus growing regions of Southern 

California, often working in cooperation with researchers 

from the Citrus Experiment Station (CES) at Riverside, experimented 

with and implemented reduced pesticide input 

pest management programs. Many of these programs were 

coupled with the release of newly imported natural enemies 

or with insectary-reared natural enemies. 

Southern California growers started relying heavily on 

biological control after the mid-1960’s once the introduced 


Photo 5. Metaphycus helvolus parasitizing a soft scale. 

Photo by A. Kapranas. 

parasitoid A. melinus started suppressing California red scale 

below levels of economic concern. Many growers in coastal 

areas started using twice annual (spring and fall) oil sprays to 

maintain key pest species such as California red scale, citrus 

bud mite (Eriophyes sheldoni), and others below economic 

levels, and were thus able to avoid the use of other pesticides. 

By the mid-1970’s, several progressive pest control advisors 

in coastal and interior Southern California had developed 

a biologically-based citrus IPM program which emphasized 

pest monitoring, selective pesticide use, and augmentative 

releases of insectary-reared A. melinus for California red 

scale control. 

Development of a biologically-based IPM program for 

SJV citrus 

During the latter period of the pesticide era, citrus production 

in the San Joaquin Valley (SJV) relied heavily on 

broad-spectrum pesticide use. Despite repeated attempts by 

pest control advisors and CES scientists to introduce various 

facets of biologically-based citrus IPM into the SJV, growers 

showed limited interest in reducing broad-spectrum pesticide 

use, and in the context of these treatments and the extremes 

of summer and winter temperatures, natural enemy effectiveness 

was limited. 

In the mid-1980’s, a group of UC Experiment Station 

scientists, Cooperative Extension advisors, and pest control 

advisors from both Southern California and the SJV (with 

funding provided by the Citrus Research Board, UC Statewide 

IPM Program, California Energy Commission, and the USDA 

Office of International Cooperation and Development) developed 

and tested a biologically-based citrus IPM program at 

the Crown Butte Ranch in Tulare County using methodologies 

and concepts originally developed in Southern California. 

After several years of research and evaluation, this IPM 

program was disseminated as a model that might be used on 

citrus throughout the SJV. The program consisted of specific, 

intensive monitoring methods, intervention thresholds, and 

selective insecticide recommendations for each of the major 

arthropod pests found on SJV citrus at that time. 

Key among these were use of sabadilla (Veratran D; at the 

time, other selective options were not available), a botanically 

derived insecticide mixed with sugar or molasses as an attractant 

for citrus thrips control, various formulations of Bacillus 

thuringiensis (Bt) for ”orangeworm” control, narrow range

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oil for citrus red mite, low rates of chlorpyrifos (Lorsban) 

for katydid, citricola scale, and initial red scale knockdown, 

and management of California red scale through augmentative 

releases of 50,000-100,000 insectary-reared A. melinus 

parasitoids per acre per year. 

The Aphytis were released every two weeks beginning 

mid-February and ending mid-November each year, for a total 

of 20 releases of 2,500-5,000 wasps per acre per release. Low 

rates of chlorpyrifos were used to reduce California red scale 

levels prior to initiating the A. melinus releases. 

This program was shown to result in reduced pesticide use 

and similar, if not higher, fruit quality and economic returns 

compared with the conventional broad-spectrum pesticidebased 

program. 

Several earlier research advances from the UC Riverside 

Entomology Department and UC IPM Program were key 

for the development of the SJV biologically-based citrus 

IPM program. Guidelines proposing economic thresholds 

and sampling methods for the lepidopterous pests on citrus, 

which are collectively referred to as “orangeworms”, were 

developed. T.S. Bellows and J.G. Morse determined the toxicity 

and persistence of commonly used pesticides to important 

citrus natural enemies, thus facilitating the choice of selective 

materials that could be used in the program. J.D. Hare 

documented that citrus red mite (Panonychus citri) economic 

thresholds used in Southern California were too low for application 

in the SJV and that SJV populations seldom resulted 

in reduced yield. D.S. Moreno and R.F. Luck documented 

the efficacy of augmentative releases of A. melinus against 

California red scale in Southern California, setting the stage 

for augmentative release strategies in the SJV. Working with 

FMC Corp., G.P. Walker, Morse, and M.L. Arpaia adapted 

technology from South Africa and Israel and showed that a 

high-pressure postharvest washer was effective in removing 

California red scale from fruit, thus allowing the economic 

threshold of this key pest to be elevated. 

Although research efforts were critical, the biologicallybased 

IPM program would not have been adopted in the San 

Joaquin Valley without extension education (Photo 6) and 

the dedication of many progressive citrus growers and pest 

control advisors. 

Photo 6. Tulare County UCCE Farm Advisor Neil O’Connell 

conducting a field day training on citrus IPM. Photo by Beth 

Grafton-Cardwell. 


Photo 7. UCR Entomologist Dr. Robert Luck (second from left) teaching growers and PCAs about biologically-based IPM. 

Photo by Beth Grafton-Cardwell. 

A number of grower meetings were held at the Crown 

Butte ranch in the late 1980s to present and discuss progress 

in development of the IPM program (Photo 7). Throughout 

the 1990s, yearly workshops were held to teach pest control 

advisors how to recognize the life stages of California red 

scale, their parasitoids, and how to determine if biological 

control was successful. Field days and video tapes on citrus 

thrips and orangeworm monitoring were produced. 

In addition, yearly roundtable discussions were jointly 

sponsored by UC Extension Specialist E.E. Grafton-Cardwell 

and the Association of Applied IPM Ecologists. In these discussions, 

pest control advisors shared information about pest 

pressures, monitoring methods, control tactics, and the level of 

success of biological control they had achieved. Smith-Lever 

and Citrus Research Board funds supported demonstration 

projects in Kern and Tulare counties that sampled pest and 

natural enemy densities in orchards utilizing biologicallybased 

versus pesticide-reliant strategies. 

Data on pest densities, natural enemy levels, degree-days, 

and the consequences of various pest management strategies 

in these orchards were discussed by extension personnel in 

grower meetings, provided as a newsletter, and posted on 

a citrus entomology Web site at the Kearney Agricultural 

Center. Organizations such as Paramount Citrus took a lead 

role in studying and transferring high-pressure postharvest 

washer technology from South Africa to San Joaquin Valley 

packinghouses. All of this activity helped to increase grower 

adoption of biologically-based IPM methods. 

Adoption of the biologically-based citrus IPM program in 

the SJV was initially slow but was accelerated by the development 

of pesticide resistance in two key pest species. Citrus 

thrips has a history of developing resistance to broad-spectrum 

pesticides used extensively for its control and, following the 

appearance of dimethoate resistance in 1980, formetanate 

resistance in 1986, and cyfluthrin resistance in 1996, growers 

became increasingly motivated to use a biologically-based 

approach in managing this pest. 

Of greater impact, however, was the appearance of 

California red scale resistance to organophosphate and 

carbamate insecticides in the SJV in 1990. Because no new 

effective chemical options were available to growers with 

pesticide-resistant California red scale, and because multiple 

applications of organophosphates and carbamates were so 

costly (ca. $160/acre per treatment), grower adoption of the 

biologically-based citrus IPM program accelerated in the early 

1990s and reached a peak in 1997 with participation of an 

estimated 10-25% of SJV growers (this estimate varies based 

on who one talks to and what one considers the threshold for 

“participation”, i.e. does one include only those that relied 

very heavily on Aphytis releases to help manage red scale 

with only very occasional pesticide use). 

Impediments to adoption of biologically-based IPM; 

shifts in insecticide use change the status of some pests 

In 1998, because of increasing problems with California 

red scale resistance, the insect growth regulators pyriproxyfen 

(Esteem or Knack) and buprofezin (Applaud) were made 

available to SJV citrus growers through a Section 18 Emergency 

registration with full registration in 2000 and 2002, 

respectively. 

Pyriproxyfen was extremely effective against California 

red scale, but unfortunately was initially quite disruptive to 


coccinellid predators such as the vedalia beetle (critical to 

cottony cushion scale control) and Rhyzobius (Lindorus) 

lophanthae, an important predator of California red scale. 

In South Africa, pyriproxyfen use led to mealybug flare-ups 

in untreated groves located near groves where it was used 

(the pesticide was sufficiently active to suppress mealybugs 

in treated groves but coccinellid predators which normally 

maintained mealybugs below economic levels were suppressed 

regionally). 

Similarly, in California, dramatic cottony cushion scale 

flare-ups were observed starting early in 1999 in biologicallybased 

citrus IPM blocks near groves using pyriproxyfen 

because of its toxicity to vedalia beetles. Unfortunately for 

California growers, malathion, methidathion (Supracide), and 

carbaryl (Sevin) were the only effective insecticides available 

for cottony cushion scale control, and these materials are 

highly toxic to natural enemies, such as A. melinus, needed 

for control of other pests. 

Based on experience from Israel and South Africa, California 

researchers were aware of the potential for secondary 

pest upsets if pyriproxyfen was used on California citrus. In 

May 1996, at the Seventh International Citrus Congress in Sun 

City, South Africa, a number of citrus growers and researchers 

listened to an impassioned talk by V. Hattingh and B.A. Tate 

describing upsets of mealybugs and cottony cushion scale 

which resulted from pyriproxyfen treatments in South Africa. 

Subsequently, six meetings of growers, pest control advisors, 

and researchers were held in 1997 at various sites in the 

SJV to discuss the likely benefits and detriments of requesting 

the Section 18 use of pyriproxyfen. Despite concerns raised 

about possible secondary pest upsets, the consensus at those 

meetings was that this insecticide was needed to deal with 

increasing populations of California red scale and the escalating 

use of organophosphate insecticides. 

As predicted, severe cottony cushion scale outbreaks were 

experienced in 1999-2000. Subsequent research by Grafton- 

Cardwell on vedalia beetle activity demonstrated that it is 

most effective in the spring and activity declines with summer 

heat. She then trained growers to delay use of pyriproxyfen 

until after vedalia had completed its springtime control of 

cottony cushion scale. Cottony cushion scale is now a sporadic 

secondary pest because of careful use (timing) of what 

Photo 8. Third instar katydid nymph on a new fruit, ready to 

begin feeding. Photo by Beth Grafton-Cardwell. 

otherwise can be a highly disruptive insecticide. 

The availability of pyriproxyfen, a very effective red scale 

control material, dramatically lessened interest in adopting 

the biologically-based IPM program for SJV citrus because, 

initially, this insecticide could be applied for red scale control 

every second or third year if red scale levels were not high. 

This is quite common when a new and effective pesticide is 

introduced – initially, it can be remarkably effective (e.g., DDT 

against many pests, parathion-red scale, dimethoate-citrus 

thrips). In addition, there is a perception that use of biological 

control is riskier and more difficult to employ compared with 

a traditional chemical control program. 

For the present, many growers will continue to rely on 

pyriproxyfen for California red scale control, but we are beginning 

to see the early stages of resistance in some areas. In 2008, 

spirotetramat (Movento) was registered for California red 

scale control, and rotating its use with pyriproxyfen will help 

with managing resistance to either product. Both pyriproxyfen 

and spirotetramat are soft on parasitoids such as Aphytis, so 

they have allowed more natural biological control of California 

red scale to occur, minimizing the frequency of use of 

either product and providing longer term control of this pest. 

Soft insecticides release secondary pests from control 

At about the same time that pyriproxyfen and buprofezin 

were registered for California red scale control, spinosad was 

registered for citrus thrips control. All three of these insecticides 

showed greater safety for most natural enemies (other 

than coccinellids-pyriproxyfen and buprofezin) and greatly 

improved worker safety because of their specificity for certain 

pest groups because they replaced organphosphate and 

carbamate insecticide use. 

There was a problem, however, with greater selectivity 

allowing several secondary pests to become primary pests. 

Citricola scale and forktailed bush katydid (Scudderia furcata) 

(Photo 8) were quite susceptible to organophosphates. 

They were easily suppressed by treatments for citrus thrips 

and California red scale during the “pesticide era”. The insect 

growth regulators used for red scale are not very effective 

against citricola scale. The spinosad treatment (and later 

spinetoram [Delegate]) for citrus thrips has a relatively short 

residual period of activity and thus is not effective in years 

with a prolonged hatch of katydids or when used against the 

larger katydid instars. With the reduction in organophosphate 

and carbamate use, these insects have become chronic pests. 

In the San Joaquin Valley, biological control agents for these 

pests do not keep them below economic levels. 

In response to increased katydid densities (Photo 9), growers 

are tank-mixing low rates of pyrethroids or organophosphates 

with the spring spinosad or spinetoram treatment for 

citrus thrips control. Low rates of broad-spectrum insecticides, 

applied in low water volume (100-200 gpa) to the outside of 

the tree during spring, are fairly well tolerated by most natural 

enemies. Thus, these treatments can control katydids and 

minimize the impact on biologically-based IPM. 

The insect growth regulator diflubenzuron (Micromite) 

and stomach poison cryolite (Kryocide) are slow-acting, but 

they are selective and can be used before petal fall to control 

katydids prior to their causing damage on fruit. Cyantraniliprole 

(Altacor) was also recently registered and is fairly 

selective. Thus, katydids can be managed through low rates 


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Photo 10. UCR Extension Specialist Beth Grafton-Cardwell 

utilizes a mobile laboratory to teach about scale pest 

management. Photo courtesy of Beth Grafton-Cardwell. 

of a broad-spectrum material or via selective insecticides. 

Citricola scale has become a serious problem in the San 

Joaquin Valley because of inadequate biological control (except 

in groves with brown soft scale) and the low threshold 

for the economic damage it causes (lowered yield and sooty 

mold production). This scale has only one generation per year 

and long periods of time when citricola scale size is too small 

for use by several species of parasitic wasps that devastate 

the scale in Southern California. In addition, most areas of 

the San Joaquin Valley appear to lack alternative hosts of the 

parasitoids such as black scale and brown soft scale. 

Initially, growers managed increases in citricola scale 

(Photo 9) in the SJV biologically-based program with low rates 

of chlorpyrifos (Lorsban). Many natural enemies of citrus 

pests have developed tolerance to low rates of organophosphates, 

especially chlorpyrifos, due to repeated exposure, and 

thus, these treatments are now considered fairly compatible 

with IPM if they occur relatively infrequently (no more than 

once a year). 

However, as citricola scale became a common pest of citrus 

in the 2000s, continued use of chlorpyrifos led to resistance in 

about 40% of citricola scale populations, with even high rates 

of chlorpyrifos failing to suppress the scale below economic 

levels for more than a single year. 

Growers began to use foliar neonicotinoids (imidacloprid 

[Provado] and acetamiprid [Assail]) for citricola scale 

control; however, this chemical group is highly toxic to most 

natural enemies, reducing the success of the biologicallybased 

program. Growers also used imidacloprid systemically 

to control citricola scale and reduce the impact on natural 

enemies. That formulation, however, is also toxic to natural 

enemies and only weakly suppresses citricola scale. The IGR 

buprofezin (Applaud) can be effective against ctiricola scale 

and is soft on parasitic wasps, thus it is a selective insecticide. 

However, both foliar neonicotinoids and buprofezin require 

direct contact to kill the scale, and thus coverage is critical. 

These insecticides do not reduce scale densities to levels as 

low as the organophosphates did before resistance became 

a problem, and they need to be used every one to two years. 

The current trend is that growers alternate selective 

insecticides (pyriproxyfen, buprofezin, and spirotetramat) 

for California red scale control with an organophosphate or 

neonicotinoid insecticide treatment for citricola scale so as 

to minimize costs and reduce the impact of broad-spectrum 

treatments on natural enemies. 

Ideally, a selective pesticide is one that reduces the target 

pest population below economic levels with limited impacts 

on important natural enemy species. In some cases, nonselective 

pesticides can be used in a selective manner based 

on when or how they are used. 

Photo 9. Heavy populations of citricola scale reduce yield of 

trees and produce honeydew that fosters sooty mold. Photo 

by Beth Grafton-Cardwell. 


Changes in pesticide practices have caused a shift in pest 

pressures in the San Joaquin Valley. The softer insecticides 

used for California red scale and citrus thrips have resulted 

in a decline of these pests. Citricola scale is now the most 

common and most difficult pest to control, requiring the use 

of broad-spectrum insecticides that disrupt the biologicallybased 

IPM program. New selective insecticides for citricola 

scale are needed to allow natural enemies affecting other 

pests to flourish. 

Meanwhile SJV growers continue to be educated in monitoring 

methods, using treatment thresholds, and are averaging 

three to four pesticide treatments per year. Again, University 

of California extension programs and Citrus Research Board 

education in the form of grower seminars, field days, a mobile

laboratory (Photo 10), Citrograph articles, online courses 

(http://classes.ucanr.org), and Web sites (www.ucanr.org/sites/ 

KACCitrusEntomology/, http://www.ipm.ucdavis.edu/PMG/ 

selectnewpest.citrus.html and www.citrusresearch.org) help 

growers and PCAs to stay informed and maintain biologicallybased 

IPM if they are interested in that approach. 

In spite of all of the recent pest and program changes, a 

number of growers and pest control advisors continue to use 

the biologically-based IPM program in the SJV, often adapting 

it based on their experience and the local situation. Based on 

sales information provided to us confidentially by producers 

and suppliers of Aphytis melinus, we estimate that ca. 1,410.8 

million and 1,338.5 million Aphytis were sold to SJV users 

in 2010 and 2011, respectively. Practitioners likely used a 

minimum of 20,000 Aphytis per acre per year (in this case to 

augment mostly chemical red scale control) and as many as 

130,000 Aphytis per acre per year (on organic citrus). If we 

estimate that the mean per acre Aphytis use is somewhere 

between 40,000 and 80,000 wasps per acre per year, then the 

above sales figures translate to between 17,246 - 34,492 acres 

in the San Joaquin being treated on average per year with 

Aphytis over the 2010 and 2011 seasons. 

Exotic pest introductions disrupt biologically-based IPM 

A second problem for growers using biologically-based 

citrus IPM in the SJV (and anywhere else for that matter) is 

the introduction of new (exotic) pest species (Table 1). The 

rate of new introductions appears to be increasing, partially 

because of greater movement of people and plant material 

between states and countries but also because of reduced 

vigilance at border entry points brought about by an emphasis 

on facilitating trade. 

When exotic pests enter a new region, they often arrive 

without the full complement of natural enemies present in 

their native range. Thus, chemical control is often needed to 

maintain damage below economic thresholds until the full 

natural enemy complex is introduced and provides adequate 

control. 

An example of a recent exotic invader is the glassy-winged 

sharpshooter (GWSS). GWSS live on citrus, as well as many 

other hosts, and vector various strains of the bacterium Xylella 

fastidiosa that cause Pierce’s Disease in grapes, almond leaf 

scorch, alfalfa dwarf, oleander leaf scorch, and several other 

diseases such as citrus variegated chlorosis and phony peach 

disease that are not yet present in California. 

Because this pest is so destructive to the grape industry, 

citrus growers are asked to control GWSS in their plantings 

to reduce the potential movement of Xylella into nearby 

grapes. The insecticide group of choice for this pest is the 

neonicotinoids, which can potentially disrupt natural enemies. 

The current GWSS treatment program attempts to reduce the 

impact of the neonicotinoids by applying them systemically 

or if as a foliar spray, waiting until late in the season. 

Other arthropod pests have also entered the state recently, 

and many of them require insecticide treatments, at 

least initially. The red imported fire ant (RIFA) (Solenopsis 

invicta) was found in February 1997 in Kern County, and 

eradication with soil treatments of pyrethroids has been 

attempted. Since then it has also shown up in large areas of 

Southern California. At present it is unclear whether RIFA 

populations will be eradicated in the SJV, but it is possible 

that this pest may eventually become established and spread 

into citrus groves there. 

The citrus leafminer (Phyllocnistis citrella) was discovered 

in Imperial County in southernmost California in 

January 2000, spread to Riverside Co. in 2002, and is now 

found throughout much of California. The citrus peelminer 

(Marmara gulosa) is well established in parts of California 

but has changed its habits, likely due to the recent introduction 

of a new biotype from Mexico in the late 1990s, and can 

cause extensive fruit damage to susceptible citrus varieties 

such as pummelos, grapefruit, and various navel oranges 

(especially Fukumoto, Atwood, and TI). Fortunately, the 

potential for biological control by parasitoids of citrus 

leafminer and citrus peelminer on bearing citrus is good, 

and thus these pests have not caused a major increase in 

insecticide use. For citrus leafminer, young plants require 

multiple insecticide treatments to maximize growth. Pheromone 

disruption methods are being developed to manage 

citrus leafminer in nurseries. 

Diaprepes root weevil (Diaprepes abbreviatus) was discovered 

in Southern California in 2005, and the larval stages are 

known to be a threat to the root systems of citrus and other 

crops, largely because they worsen the impact of soil diseases 

such as Phytophthora. Eradication of Diaprepes was initially 

attempted, but in part due to the State’s fiscal situation, this 

was discontinued in 2008. If it spreads to commercial citrus 

production areas, it will require several treatments a year, 

including several broad-spectrum insecticides such as pyrethroids 

and neonicotinoids, potentially disrupting IPM and 

Table 1. Exotic pests recently invading California citrus. 

Common name Scientific name Damage Detection in California 

Glassy-winged sharpshooter Homalodisca coagulata Vector of Pierce’s Disease in neighboring grapes Mid 1990s 

Reduced fruit production in citrus exposed to extremely high densities 

Red imported fire ant Solenopsis invicta Damage to young plantings of citrus 1997 

Human health hazard 

Citrus peelminer (Mexican strain) Marmara gulosa Reduction in pack-out due to mining of the rind of 1998 

susceptible varieties 

Citrus leafminer Phyllocnistis citrella Attacks new foliage, can reduce growth of plants in nurseries 2000 

and new plantings 

Diaprepes root weevil Diaprepes abbreviatus Larvae attack the root system of citrus trees making trees 2005 

more vulnerable to pathogens 

Asian citrus psyllid Diaphorina citri Transmits the bacterial pathogen that causes huanglongbing 2008 


greatly increasing costs to growers. 

The impacts of the above exotic pests are likely to appear 

mild in comparison to the Asian citrus psyllid (ACP), in 

particular if the bacterial disease it vectors, huanglongbing 

(HLB), is found in California. 

HLB is moving northward towards California from 

Mexico and was recently discovered in commercial citrus in 

Texas. This disease has had serious impacts on citrus production 

in China, Brazil, Florida, and elsewhere and has been the 

subject of many recent Citrograph articles. Thus, we will not 

address ACP and HLB in detail here other than to say that 

experience in Florida has clearly shown that to-date, the most 

effective strategy of managing HLB is via effective, regional 

insecticide treatment programs for ACP, which ideally include 

all commercial growers in the region. 

We still have much to learn about adapting the experience 

with ACP and HLB management from other states and 

countries for optimal use in California. In the long term, we 

are optimistic that research will develop a practical solution to 

ACP and HLB management that does not require continual 

broad-spectrum pesticide applications and maximizes the 

use of biological control of ACP to the extent that is feasible. 

Because of the severity of HLB, in the interim, we may go 

through a rocky period as we learn how to best deal with ACP 

and determine what sort of chemical program will cause the 

least impact on natural enemies and the upset of secondary 

pests that often results. If we can weather the ACP-HLB storm, 

we believe biologically-based IPM holds tremendous promise 

regarding the future of citrus pest management. 

It is important to note that the level to which a particular 

grower and/or pest control advisor adopts biologically-based 

citrus IPM varies tremendously across the SJV and, in reality, 

there is a spectrum of adoption varying from those who 

emphasize biologically-based IPM by severely limiting the use 

of pesticides which impact natural enemies to those who rely 

heavily on chemical control and are not as concerned with the 

occasional use of broad-spectrum pesticides. 

Most growers and pest control advisors are in the middle 

of this spectrum and would adopt biologically-based IPM 

to a greater degree if some of the more difficult challenges 

to this approach were solved (e.g., selective management of 

citricola scale, citrus peelminer on some varieties, and ACP 

once it enters the SJV). 

Conclusions 

Successful Biologically-Based IPM and Impediments to 

its Adoption and Success: 

1. The success of the program depends on intensive 

sampling of pest and natural enemy populations in order 

to maximize the effectiveness of soft pesticides and natural 

enemy populations. 

2. Developing the required level of knowledge and training 

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needed to successfully conduct biologically-based IPM for a 

crop system as complex as citrus takes years of experience 

and input from knowledgeable pest control advisors and 

supportive growers. 

3. There is a learning curve associated with the adoption 

of biological-based IPM in the SJV, and the “system” does not 

stabilize for a year or two after the conversion from an IPM 

program based more on pesticide use. To make the program 

work effectively, a commitment to biologically-based IPM 

is needed by knowledgeable growers and their pest control 

advisors. 

4. The biologically-based citrus IPM program is both 

sustainable and dynamic, due to changes in pesticide registrations, 

pest complexes, and the introduction of exotic species. 

Research, extension, and management programs have to be 

equally dynamic to respond to those changes. 

For the immediate future, further adoption of the biologically-based 

citrus IPM program in the SJV depends on the 

motivation of growers and PCAs who are interested in this 

approach. Unfortunately, this approach is likely to become 

more difficult, rather than easier, once the industry has to 

deal with the presence of ACP (and hopefully much later, 

HLB) in the SJV. 

For some people, an IPM program emphasizing chemical 

pest control appears to be a simpler pest management solution, 

and this approach may be absolutely essential to effectively 

dealing with ACP and HLB. However, experience with 

citrus has shown that this approach is not sustainable over the 

long term (pesticide resistance being one recurring problem) 

and is more costly than biologically-based IPM. 

Acknowledgments 

Development of the biologically-based citrus IPM program 

for SJV citrus would not have been possible without 

the input and assistance of a large number of individuals and 

agencies. Robert F. Luck; Harry Griffiths and Joe Barcinas of 

Entomological Services, Inc.; Frank Marshall of Central Valley 

Management, Inc.; Neil O’Connell, UC Cooperative Extension, 

Tulare County; Craig Kallsen, UC Cooperative Extension 

Kern County; Lisa Forster, Phil Haney, and Alan Urena of UC 

Riverside; the UC Riverside Entomology staff at the Lindcove 

Research and Extension Center (Ashley Derr, Janine Lee, 

Janet McClain, Melissa O’Neal, Yvonne Rasmussen, and Chris 

Reagan) and the Kearney Ag Center (Ping Gu, Greg Montez, 

Yuling Ouyang, Becky Striggow, and Stacy Vehrs); and Jim 

Stewart and Jim Gorden of Pest Management Associates, 

Inc. were all instrumental in helping to develop this program, 

as was funding provided by the California Citrus Research 

Board, the UC Statewide IPM Program, Smith-Lever funds, 

the California Energy Commission, and the USDA Office of 

International Cooperation and Development. 

This article is an update of a 2006 article that was published 

in the UC Plant Protection Quarterly. 

Dr. Joseph G. Morse is a Professor of Entomology with 

the Department of Entomology, University of California 

Riverside. Dr. Beth Grafton-Cardwell is a University of California 

Extension Specialist and Research Entomologist. She 

is a Citrus IPM Specialist in the Department of Entomology 

at UC Riverside and also serves as Director of the Lindcove 

Research and Extension Center. l 

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What are the University of California sources for 

citrus integrated pest management information 

Beth Grafton-Cardwell 

The University of California Integrated 

Pest Management Program 

(UC IPM) provides hundreds of 

pages of excellent information in print 

form and on the Web that explains how to 

recognize and manage pests and diseases 

of citrus. 

Below I discuss the three major components 

of these guidelines and their uses. 

While the citrus manual and guidelines 

have been around for decades, and most 

growers and PCAs are familiar with 

them, the Year-Round IPM Program for 

Citrus approach is less well-known, but 

extremely useful, especially for those 

who are new to citrus. I encourage you to 

explore these pages. 

Citrus IPM Manual - NEW THIRD 

EDITION Available March 2012! 

The previous edition of the Citrus 

IPM Manual was published in 1991. The 

new edition incorporates changes in our 

knowledge of various endemic vertebrate, 

weed, nematode, insect and mite pests 

and diseases and introduces a number of 

recently invading species. 

During the past 15 years, glassywinged 

sharpshooter, citrus leafminer, a 

new strain of citrus peelminer, diaprepes 

root weevil and Asian citrus psyllid have 

established in California. In addition, the 

manual provides photos of a number of 

diseases that have not yet reached California, 

including citrus bacterial canker, 

huanglongbing, citrus variegated chlorosis 

and citrus leprosis. 

The new edition emphasizes photorecognition 

of citrus pests and diseases and 

is an essential manual for the library of anyone 

with an interest in citrus management. 

UCIPM Citrus Pest Management 

Guidelines http://www.ipm.ucdavis. 

edu/PMG/selectnewpest.citrus.html. 

The UCIPM citrus pest management 

guidelines provide information on all of 

the significant pests and diseases of citrus 

(Figure 1). For each pest or disease, the 

guidelines describe its lifecycle, the damage 

it causes to citrus, natural enemies that 

attack it, monitoring methods, organically 

acceptable methods of control, selectivity 


Fig. 1. A snapshot showing a portion of the available information in the UC 

IPM Citrus Pest Management Guidelines. http://ucipm.ucdavis.edu/PMG/ 

selectnewpest.citrus.html 

Fig. 2. A snapshot of the first page of the year-round IPM program for Central 

Valley citrus. http://ucipm.ucdavis.edu/PMG/C107/m107yi01.html

of pesticides, resistance issues and pesticide 

treatment choices. 

It is an excellent reference source for pest 

control advisors and growers to make decisions 

about when to treat and what to treat 

with. The guidelines also have important 

links to pages such as “mandatory intervals 

between application, reentry (REI), and 

harvest (PHI) and hazards to bees”. This 

section is very helpful as a quick check for 

which pesticides are registered for citrus as 

well as their use restrictions. 

Fig. 3. The annual checklist for the citrus year-round IPM program. http:// 

ucipm.ucdavis.edu/PMG/C107/citrus-checklist.pdf 

UCIPM Year-Round IPM Program for 

Central Valley Citrus 

http://www.ipm.ucdavis.edu/PMG/C107/ 

m107yi01.html 

In 2008, University of California farm 

advisors, extension specialists and researchers 

worked with UC IPM to develop a “Year- 

Round IPM Program for Central Valley 

Citrus” (Figure 2). The year-round program 

provides perspective on when activities 

should occur during the year (pre-bloom, 

bloom, petal fall, fruit development and fall). 

For example, during the pre-bloom 

period, PCAs are advised to monitor for 

California red scale, mites, cottony cushion 

scale, earwigs, katydids and brown garden 

snails. They are also advised to watch for 

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Fig. 4. The forms and photo identification pages for the citrus year-round IPM 

program. http://ucipm.ucdavis.edu/PMG/C107/m107yiformsphotos.html 

diseases such as bacterial blast, brown rot, 

dry rot, and Phytophthora as well as survey 

winter weeds and search for signs of vertebrate 

pests. 

For each of these pests or diseases, the 

details of how to monitor are provided using 

links to text, photos, and monitoring forms. 

The photos and monitoring forms (Figure 

4) are easily downloaded and printed. The 

monitoring forms are especially helpful for 

PCAs new to citrus, providing consistent 

methods of sampling that allow orchard pest 

and disease populations to be compared. 

The Citrus Year-Round IPM Program 

also includes an 8-page annual checklist 

that can be printed out and used throughout 

the year. The checklist is an excellent way 

to demonstrate to regulatory agencies and 

employers that you are using integrated 

pest management tactics to manage pests 

and diseases. 

A University of California Extension 

Specialist, Dr. Beth Grafton-Cardwell is a 

Citrus IPM Specialist in the Department of 

Entomology at UC Riverside and serves as 

the Director of the Lindcove Research and 

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CRB 2011 Annual Report 

Ted Batkin, President 

The 2011 fiscal year brought about several 

changes and also some degree of stability. 

First, the program changed the fiscal year 

from 1 November to 1 October. This resulted in an 

11-month year, so many of the figures in the budget 

report are a bit different from a normal 12-month 

year. Second, the Operations program is in its third 

year, so there is a level of stability in that program and 

the work is going smoothly. The Operations program, 

which is funded through a contract with the Citrus 

Pest and Disease Prevention Program (CPDPP), 

remains focused on maintaining a strong Asian citrus 

psyllid detection program in commercial groves and 

laboratory testing for HLB. 

For the research program, advances were made in 

the development of an ACP trap with some level of 

attractant. This work is now at the field-testing stage, 

and several of the compounds are showing promise 

to improve the traps. In the area of diagnostics, the 

year brought notable progress in the VOC detection 

system and the Lateral Flow Microarray device. Both 

of these platforms are moving towards commercialization 

and should be available to the industry within 

the next two years. ACP control still is a focus of the 

research agenda, and several new projects were initiated 

to help with field efficacy issues. 

The Jerry Dimitman Laboratory in Riverside is 

now fully certified by USDA-APHIS and processing 

both leaf samples and ACP samples for the presence 

of the bacteria associated with huanglongbing. 

In addition, the Board completed an expansion of 

the facilities to improve the capacity for sample 

processing and to provide room to conduct methods 

development from CRB-funded research projects. 

The Board welcomes your comments and observations 

to the Citrus Research Program. The 

following table lists the audited financial statement 

for the 2011 fiscal year. A complete copy of the audit 

is available for viewing at the CRB office at 217 N. 

Encina, Visalia, CA. You are welcome to visit us at 

any time to discuss any elements of the program and 

see what we are doing. This is your program, and we 

look forward to hearing from you. l 

CITRUS RESEARCH BOARD 

November 1, 2010 through September 30, 2011 

INCOME 

2010-2011 FY Assessment Income............... 5,928,276 

Prior Season Income........................................ 144,197 

Investment Interest Income................................ 26,527 

Investment Dividend Income............................... 21,087 

Rent..................................................................... 2,117 

Citrograph Advertising........................................ 27,874 

Conference Registration Fees............................. 11,183 

Outside Income................................................ 125,000 

Grower Seminar Registration................................ 8,770 

Reimbursed Expenses...................................... 137,500 

CPDPC Reimbursement Income..................... 2,744,585 

TOTAL FUNDS AVAILABLE........... 9,177,116 

EXPENSES 

RESEARCH PROGRAM 

Plant Management 

DMS VOC Sensor for Citrus............................... 270,000 

Bio Sensor Development for 

Citrus Disease Diagnosis.................................. 114,887 

Determination of Timing..................................... 28,000 

Total Plant Management............................... 412,887 

New Varieties 

Citrus Rootstock Evaluation.............................. 111,191 

Variety Evaluation for Trueness........................... 71,823 

New Citrus Breeding......................................... 163,406 

Evaluation of Desert Lemons.............................. 13,006 

Unforbidden Fruit: Preventing Citrus Smuggling..... 4,884 

Total Plant Improvement............................... 364,310 

Plant Pathology 

Septoria Spot of Citrus.........................................45,375 

Small RNA for HLB Plant Response....................104,769 

Investigation of Seedling Yellows Cross...............69,540 

Identification of Spiroplasma citri........................58,600 

Investigating Important Disease...........................82,249 

Integrated Low Cost Nucleic Acid.......................151,448 

Development, Validation & Deployment..............245,000 

Rapid Identification of Unknown Viroid.................75,217 

Avoiding Economic Losses in CA Citrus...............48,092 

Total Plant Improvement............................... 880,290 


Entomology 

Pest Management Infrastructure....................... 187,871 

Management of Thrips........................................ 69,692 

Assessment of Systemic Neonicotinoid............. 128,502 

Molecular Systematics of Diaphorina.................... 8,092 

Optimization of Imidacloprid Application Rates.... 36,700 

Host Specificity Testing of Tamarixia................... 74,929 

Preparation for Citrus Leprosis........................... 25,205 

Evaluation of Oils.................................................. 6,250 

ACP Attractants................................................ 288,853 

Development of Pathogen Dispenser to 

Control ACP...................................................... 114,400 

Optimizing Chemical Control of ACP in CA........ 102,603 

Maintenance of Foundation ACP........................... 8,226 

Total Entomology........................................ 1,101,323 

Post Harvest 

Treatment Evaluation.......................................... 47,250 

New Technologies to Minimize P.H. Decay........... 50,000 

Ethyl Formate Studies for Bean Thrips................ 63,945 

Breaking Citrus Trade Barriers............................ 26,243 

Assessing Factors Influencing Post Harvest Quality.. 55,758 

Total Post Harvest.......................................... 243,196 

TOTAL RESEARCH PROGRAM...................... 3,002,006 

COMUNICATIONS PROGRAM 

Core Grower Education Program..........................33,543 

Citrograph.........................................................103,848 

Website.................................................................9,109 

CPDPP Outreach Program..................................674,164 

Salaries & Benefits - Communications...............181,456 

Supplies................................................................1,051 

Travel....................................................................1,559 

TOTAL COMMUNICATIONS PROGRAM......... 1,004,730 

CITRUS CLONAL PROTECTION PROGRAM 

Core Citrus Clonal Protection Program...............386,403 

LREC Positive Pressure Greenhouse..................144,772 

TOTAL CITRUS CLONAL 

PROTECTION PROGRAM................................. 531,175 

OPERATIONS PROGRAM 

Data Management 

Salaries & Benefits – Data Management........... 140,685 

Travel & Mileage.................................................. 1,343 

Training................................................................ 1,495 

Information Services........................................ 121,505 

Supplies.................................................................. 834 

Phone................................................................... 2,166 

Total Data Management................................ 268,028 

Laboratory – Riverside & Visalia 

Salaries & Benefits – Lab................................. 151,773 

Travel & Mileage.................................................. 4,422 

Equipment Repairs............................................. 10,215 

Supplies........................................................... 100,197 

Utilities............................................................... 14,121 

Phone................................................................. 14,158 

Postage................................................................... 179 

Rent.................................................................. 36,911 

Total Laboratory – Riverside & Visalia.......... 331,976 

Field 

Salaries & Benefits – Field................................ 192,127 

Contracts (Outside Personnel)............................... 8,108 

CASS Staffing................................................... 479,335 

Trap Readers...................................................... 92,406 

Travel & Mileage ............................................... 15,153 

Fuel.................................................................... 93,870 

Vehicle Repairs & Maintenance........................... 35,571 

Equipment Repair & Maintenance......................... 4,652 

Supplies............................................................. 99,058 

Phone................................................................. 16,493 

Postage................................................................ 2,824 

Total Field.................................................... 1,039,597 

Administrative Support....................................................91,667 

TOTAL OPERATIONS PROGRAM.................. 1,731,260 

PAYROLL EXPENSE – 

Communications, Operations & Admin................... 93,144 

CALIFORNIA CITRUS QUALITY COUNCIL (CCQC) 

CCQC Administration........................................ 251,310 

Registration Projects.......................................... 20,660 

International Issues.......................................... 152,450 

Other Projects.................................................... 11,466 

TOTAL CALIFORNIA CITRUS QUALITY 

COUNCIL (CCQC)............................................ 435,886 

CONFERENCES..........................................29,620 

GENERAL AND ADMINISTRATIVE 

Salaries & Benefits – Administration................. 522,615 

Audit Fee............................................................ 12,817 

Equipment Repair & Maintenance......................... 3,613 

Equipment Rental................................................. 1,916 

Information Services.......................................... 37,898 

Insurance & Bonds............................................. 19,829 

Workman’s Compensation Insurance.................. 10,458 

Office Supplies................................................... 20,479 

Postage................................................................ 5,711 

Printing.............................................................. 10,496 

Rent & Storage................................................... 21,400 

Research Consultant.......................................... 10,000 

Meeting Costs.................................................... 37,269 

Telephone.......................................................... 17,844 

Travel & Mileage – Consultant................................. 935 

Travel & Mileage – Members.............................. 45,541 

Travel & Mileage – Staff..................................... 57,146 

Vehicle Maintenance & Fees.................................... 663 

CDFA – Bureau of Marketing.............................. 52,558 

CDFA – Handler Audit......................................... 23,625 

Building Repairs................................................... 2,456 

Property Taxes...................................................... 4,840 

Utilities............................................................... 10,538 

Depreciation..................................................... 180,660 

TOTAL GENERAL & ADMINISTRATIVE........... 1,111,307 

TOTAL EXPENSES................................ 7,939,137 

TOTAL CASH RESERVES................................... 2,756.653 

TOTAL ASSETS...................................................... 5,160,450 


Citrus Roots 

Preserving Citrus Heritage Foundation 

Help! Can you identify the 

packer and the location 

California Citrus 

Spurred Colonization– 

Aided Through the 

University of California... 

Richard H. Barker 

Your Foundation through the work of Tom Pulley 

is compiling a list of citrus brands of each packer… 

A FIRST! We have listed 6,870 so far, and we 

are still going. We want to match a packinghouse 

photo to the majority of the packers on this list, 

and that is where you enter! 

WE NEED YOUR HELP IN FINDING PHOTOS 

OF CITRUS PACKERS IN 

Delano 

Dinuba 

Dixon 

Edison 

Exeter 

Fairoaks 

Hamilton City 

Ivanhoe 

Lemon Cove 

Lindsay 

Orange Cove 

Check out our website… 

www.citrusroots.com 

Our “Mission” is to elevate the awareness of 

California citrus heritage through publications, 

education, and artistic work. 

We are proud of our accomplishments as a volunteer 

organization, which means each donated 

dollar works for you at 100% [for we have no 

salaries, wages, rent, etc.]. All donations are tax 

deductible for income tax purposes to the full 

extent allowed by law. 

Citrus Roots – Preserving Citrus 

Heritage Foundation 

P.O. Box 4038, Balboa, CA 92661 USA 

501(c)(3) EIN 43-2102497 

The views of the writer may not be the same as this foundation. 


Orosi 

Oroville 

Palermo 

Porterville 

Rocklin 

Seville 

Strathmore 

Terra Bella 

Visalia 

Woodlake 

Commendation is given to the University of California’s 

College of Agriculture for the work of E. W. Hilgard 

and for the Demonstration Trains “California Agriculture 

Special”and “Frost Education Special”. The latter provided 

the opportunity of promoting the Experimental Station for 

citrus research… All due to the help of the Southern Pacific 

Company... 

As a prologue, our focus will start when Eugene W. 

Hilgard first came to the University of California 

in the mid-1870s. He brought a background in geology, 

mineralogy, chemistry, zoology and botany coupled with 

experiences in the central states and Spain. 

One would conclude that he was uniquely suited for his 

30-year career at the university. As F. Slate described his 

personality in his “Biographic Memoir of Eugene Woldelmar 

Hilgard (1833-1916)”, “Many have marveled that a fighting 

exponent of personal views in the public arena can be radiant 

of unassuming gentleness at home.” 

Eugene Hilgard is remembered because of his pioneering 

work in California relative to soils -- “alkali-soil” and 

“arid fertility.” His initial landmark “call to fame” was his 

scientific study presented by soil maps, which were published 

as part of the 1880 U. S. Census. 

As Richard J. Orsi built the “case” in his book “Sunset 

Limited - The Southern Pacific Railroad and the Development 

of the American West 1850-1930”, the University of 

California’s College of Agriculture did not have the financial 

means, the capacity, or the capability of amassing the data of 

this scale, and it was the Southern Pacific which opened their 

immense collection for Hilgard to utilize in compiling these 

soil studies. 

Further, Orsi mentioned that the railroad company 

sent a young civil engineer, Norman J. Willson, to work with 

Hilgard, and for over three months he conveyed a handcar 

over most of their route collecting over 400 specimens and 

samples for this study. 

Had it not been for the support of the Southern Pa-

Volume I of III 

Including a fold out 

time line chart of 

by Marie A. Boyd and Richard H. Barker 

Volume III of III 

$ 15 00 

cific, these maps could not have been completed in such 

exactitude. The University’s College of Agriculture would 

not have been credited with this exemplary work, and the 

Southern Pacific would not have had these noteworthy documents 

to support their land promotions. 

From Hilgard’s successful work, the rail company took 

every opportunity to maximize their efforts from his findings. 

They concluded on having local irrigated demonstration 

gardens spotlighting trees, shrubs, and other plants 

which were adaptable to the soil and climate of each location. 

The selection was focused on beauty as a means of 

market appeal, though most importantly the highlighted 

horticulture example they chose to plant had a potentiality 

of becoming a high-traffic commodity. 

These “gardens” were located in key station areas and 

their various hotels. Supporting horticultural material on 

behalf of the University of California and the Southern Pacific 

Company was available at each “garden site.” Those 

“gardens” were successful in furthering colonization and 

development; one only needs to look at the citrus development 

in Southern California, the pioneering of citrus in the 

Central Valley, cotton in the area of Roseville, alfalfa in the 

Imperial Valley, etc. 

In the photo of the Southern Pacific Park (garden) in 

Pomona, in support of the above, when the train stopped 

for loading and unloading the passengers had a short opportunity 

to stroll and view this narrow, block-long park 

and enjoy the beauty of the flowers, the targeted scheme 

of planted shrubs, the citrus varieties and other fruit trees. 

Brilliant marketing resulted when the University of California, 

Southern Pacific Company, and the community worked 

together. 

Politics and the UC budget 

Now, with the background of the Prologue, we can turn 

our attention to the period of 1900 to 1917, our nation’s 

Progressive Period (the interval of Presidents were Theodore 

Roosevelt to Woodrow Wilson). It was a time when 

the middle-class Americans believed that they needed to 

restore the government to the hands of the people. Government 

should be in the interest of the many rather than just 

the few. (The aforementioned keeps echoing -- history does 

repeat itself!) 

Further, one percent of the population owned 50 per- 

Citrus Roots Series... 

GIFT IDEAS!! 

Citrus Roots...Our Legacy - Volume IV 

Citrus Powered the Economy of Orange County 

for over a half century Induced by a “Romance” 

All donations are tax deductible for income tax 

purposes to the full extent allowed by law. 

For ordering information 

visit our website 

www.citrusroots.com 

Citrus Roots 

Preserving Citrus Heritage Foundation 

The Southern Pacific Railroad Park in Pomona. Travelers 

could stroll through the narrow, block-long park and view 

the special trees, shrubs, and other plants adaptive to the 

soil and climate. Various citrus varieties were on-site. 

cent of the country’s wealth. With this setting, we can now 

obtain a better understanding of the public attitude and 

their emotional feelings toward any sizable organization. 

Large institutions were looked upon with distrust. The 

Southern Pacific Company stood out as the largest corporation 

in the West. 

The University of California was looked upon as powerful 

-- and as an elitist -- hence, its budget was slashed. These 

budget cuts drove the University and the College of Agriculture 

to Southern Pacific, for each had common-like goals to 

develop farm commodities. The programs of the university 

to advance “scientific farming” were being totally ignored. 

The Southern Pacific Company offered to help by having 

their local station agents distribute agricultural bulletins 

and assist in advertising the university forums offered 

to farmers. The company even developed programs under 

which farmers could take advantage of drastically reduced 

fares to attend these meetings offered by the university. 

Bringing the farmers to the University of California’s College 

of Agriculture did not work! The University became 

convinced that it had to go directly to the farmer. 

A ‘university on wheels’ 

This was conceived as a “university on wheels” by 

Benjamin I. Wheeler, president of the University. He also 

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Keeping citrus heritage alive in the minds of those living in California through publications, educational exhibits and artistic works 


named it “An Evangel Train.” The Southern 

Pacific Company mapped the itinerary, made 

schedules, worked with community businesses, 

farm organizations, etc. Additionally, the rail 

agents publicized each visit. The Company also 

provided food and sleeping cars plus paid the 

bills as reported by historian Orsi in his book 

mentioned earlier, “Sunset Limited The Southern 

Pacific Railroad and Development of the 

American West 1850-1930”. 

The rolling of the “California Agriculture 

Special” demonstration trains covered three 

seasons: 1909-1910, 1910-1911, and 1911-1912. 

In 1911-1912, which was the peak, the train 

traveled between 4,000 and 5,000 miles, made 

238 stops, and attracted 102,000 visitors. 

This “California Agriculture Special” train 

visited practically every town of importance 

within the citrus belt of Southern California. G. 

Harold Powell gave a presentation at many of 

the stops on citrus pests, spraying methods, and 

predatory insects used to control insects; additionally, 

experiments were conducted on new and better 

varieties of oranges and lemons. 

The “trains” were most important in helping modernize 

California agriculture. During the latter tours, women 

professors from the Department of Home Economics gave 

discussions on food preparation, labor-saving devices, and 

public health issues. 

The public resentment changed from this spotlighted attention. 

Further, the California legislature took a more positive 

attitude, which resulted in greater allotments of funding 

for programs and buildings. 

A special frost education train 

During the end of December 1912 and January 1913, a 

devastating freeze struck the citrus areas. The $175 million 

Railcar exhibit area. One of many. 


Benjamin I. Wheeler, president of the University of California, is at the 

center of the group (middle row, fifth from left). 

Southern California citrus industry was under siege and 

hoping for survival! Some estimated a 39 percent loss of 

crop, and the total tree loss was very high. 

The Southern Pacific and the University of California 

proactively came together, and the cars rolled again, this 

time as the “Frost Education Special” to the help of the 

grower to minimize long-term damage and to prepare them 

for another, future freeze. The help was through giving advice 

as to pruning, irrigation, fertilization, and other important 

recommendations. 

The schedule included 24 cities starting on February 

13th and continuing to February 18th, from 9:00 a.m. to 9:00 

p.m. Newspapers carried very positive wrap-ups of the tour. 

As reported by the Los Angeles Times (February 12, 1913), 

present were: T. F. Hunt, dean and director; H. J. Webber, 

director of the Citrus Experimental 

Station; E. J. Wickson, ex-dean 

and director; W. T. Clark, superintendent 

of Farmers’ Institute; J. E. 

Coit, professor of citriculture; J. S. 

Burd, chemist in charge of fertilizer 

control; and, J. B. Neff, conductor 

of Farmers’ Institutes for 

Southern California. 

President Wheeler of the University 

became a regular speaker, 

and General Manager Powell of 

the California Fruit Growers Exchange 

was a party during part 

of the trip. Again, all was paid for 

by the Southern Pacific Railroad 

Company. 

Now, what made this a special 

opportunity was the fact that the 

population of growers widely attended 

these 24 stops. This gave 

the University a perfect audience 

to sign a petition and a resolution 

calling for the passage of a bill

then pending in Sacramento, the legislation to appropriate 

$385,000 to establish a University Experimental Station for 

citrus research. 

A “golden opportunity” and a “golden ending”! On 

December 14, 1914, the University of California approved 

Riverside as the site selection. The Mission Inn rang its bells, 

and the electrical plant blew its steam whistle for 15 minutes. 

This is just another positive story involving two major 

players working together to advance the California citrus 

industry. 

(The complete L.A. Times, Feb. 12, 1913, article on the 

“Frost Education Special” will be posted on the Foundation’s 

website.) 

Richard H. Barker is the founder and president of the 

Citrus Roots-Preserving Citrus Heritage Foundation. For 

a number of years, he has been leading a drive to bring 

about a higher awareness of the role citrus played in developing 

California. Dick is a retired investment banker and 

was a third generation Sunkist grower. He has published 

four volumes on citrus heritage. 

All illustrations for this article were sourced by the author, 

who writes that he is especially indebted to the staff at 

the Bancroft Library at UC Berkeley for their perseverance 

in searching their archives for photographs. The photo of the 

Southern Pacific Park in Pomona is from the Pomona Public 

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CRB Funded Research Reports 

Research Project Progress Report 

Reagentless detection of citrus pathogens using 

differential mobility spectrometry (DMS) 

Alexander A. Aksenov, William Cheung, Weixiang Zhao, Hamzeh Bardaweel, 

Federico Martinelli, Oliver Fiehn, Abhaya M. Dandekar and Cristina E. Davis 

Huanglongbing (HLB) and tristeza (caused by Citrus 

tristeza virus [CTV]) are both destructive citrus diseases 

capable of severely limiting citrus production. 

To date, millions of trees throughout the world have been destroyed 

due to CTV infection alone. In certain areas of south 

Florida, the majority of trees in some orchards are known to be 

affected by HLB. As such, both diseases represent a significant 

burden to the citrus industry across the world, reducing the 

quality and the total amount of citrus production annually. 

The primary goal of this project is to develop an early-stage, 

rapid, and non-invasive means of detecting these 

pathogens via analysis of the volatile organic compounds 

(VOCs) emitted by citrus plants as their metabolism changes 

after infection. This approach would complement existing 

HLB and CTV detection techniques such as real-time polymerase 

chain reaction (RT-PCR), electron microscopy and 

serological testing already in use. 

The VOCs emitted by plants are typically associated 

with the distinctive aroma of the specific plant species and/or 

varietals (e.g. fresh smell of pine forest, jasmine, basil, mint). 

The “fresh citrus” smell is mostly 

due to presence of terpenes, a class 

of organic compounds that are derivatives 

of the isoprene pathway. 

VOCs an indicator of plant health 

The released VOCs are closely 

associated with plant metabolism, 

therefore serving as an indicator 

of plant health status. The changes 

in VOC production can occur due 

to a variety of conditions, including 

changes in environment, water 

stress, nutrient status, or the presence 

of pathogens. 

The VOCs typically must be 

present in relatively high concentration 

to reach our human “olfactory 

threshold” to be detected by the human 

nose but in lower concentration 

for a dog’s nose. Out of thousands 

of chemical compounds released 

by plants, most will be present at 

concentrations significantly below 

the olfactory threshold of the hu- 


Fig. 1. Sampling of VOC using portable DMS unit. 

man nose (e.g. we don’t smell them, but they are still present 

at very low amounts). The application of a highly sensitive 

method to conduct VOC screening, which will allow us to 

detect and identify those trace level VOCs, will open a new 

avenue for monitoring overall plant health in many different 

biological systems. 

Our first approach was to examine this in citrus, given 

the acute need of the industry to diagnose and track HLB 

spread across infected orchards. 

Plants respond to the presence of a pathogen by hostpathogen 

interactions that result in changes in metabolic activity; 

some of these changes will affect volatile metabolites, 

which in turn will result in an alteration of the emitted VOC 

profile. Some VOCs may undergo down- or up-regulation, 

and certain metabolites may be associated with particular 

stages of the pathogen’s life cycle within the plant host. 

Stimulation of VOC production is often described by 

use of the term “induced VOC” (IVOC). The detection of 

the entire IVOC profile in a fast, reliable and reproducible 

manner that will allow the monitoring of plant health will 

provide a very valuable tool for the 

agricultural industry in general and 

the citrus industry in particular. 

At the same time, this poses a 

formidable challenge. Application 

of certain analytical techniques for 

VOC detection may be limited due 

to low sensitivity, insufficient resolution, 

high cost, or a lack of portability, 

which is essential for realtime 

and in-field measurements. 

Differential mobility spectrometry 

(DMS) is also commonly 

known in scientific circles as high 

f ield asymmetric waveform ion mobility 

spectrometry (FAIMS). It is 

a very suitable technology for the 

outlined challenges associated with 

VOC detection in agriculture mentioned 

previously. 

Use of DMS technology 

The micro-machine DMS is a 

very small and portable device that 

has great sensitivity and specificity

and a relatively low power consumption. It functions to detect 

a large number of volatile and semi-volatile compounds, 

even at very low concentrations — from parts-per-million 

down to parts-per-trillion thresholds. The DMS technology 

belongs to the family of other ion mobility (IM) chemical 

detection methods which exploit differences in gas-phase 

behavior of ions under various applied electric fields. 

The drift time ion mobility spectrometry (DT-IMS) is a 

very well established technology that is used extensively for 

security applications (e.g. airport screening for explosives and 

narcotics), military applications (e.g. detection of chemical 

warfare agents), and other trace compounds detection needs. 

The DMS technology utilizes differences in ion behavior 

under low and high field conditions for various ionic chemical 

species, unlike the DT-IMS method where ions are driven by 

relatively weak electric fields. In the DMS system we employ 

in this study, volatiles are sampled through low-pressure inlet 

(“sniffing”), ionized, then 

passed between two small 

metal electrodes using an appropriate 

sampling “carrier” 

gas (e.g. dried room air). 

A specifically-shaped 

radio-frequency (RF) electric 

field waveform is applied 

across the electrode pair. If 

the mobility of a sampled 

chemical is different under 

high- and low-field conditions, 

the chemical will experience 

net displacement 

toward one of the electrodes 

and will be neutralized (i.e., 

we cannot “see” it). An additional 

direct current (DC) 

voltage, called a “compensation 

voltage” (CV), is applied 

to the RF electrode to offset ion displacement and allow a 

particular chemical species to pass through the device — effectively 

acting as a filter. 

Each chemical species has a unique dependence of its 

mobility due to the electric field (chemical signature); therefore 

the differences in ion mobilities under high- and lowfield 

conditions can be used to identify specific chemicals. 

Variation in the amplitude of the asymmetric waveform 

will alter ion behavior and may result in different CV. Thus, 

using such amplitude scan in addition to the CV monitoring 

allows a significant enrichment of information from each 

measurement. This is a critical advantage of the DMS method 

compared to the DT-IMS for the discrimination of extremely 

complex samples such as VOCs off-gassed by citrus trees. 

In addition, the DMS can be coupled with other separation 

methods such as gas chromatography (GC/DMS), further 

increasing diagnostic capability. In a GC/DMS experiment, 

each chemical can be separated and characterized by 

their respective CVs and retention times, both indicative of 

a particular chemical species. 

Fig. 2. An example of DMS data for VOCs produced by orange 

tree leaves. The left panel shows detected positively charged 

ions; the right panel shows detected negatively charged ions. 

Potential for miniaturization 

An important advantage of the DMS technology is its 

potential for further miniaturization. The commercial application 

of the DMS has only been around for about 10 years, 

and a constant stream of developments have already lead to 

the development of units that are briefcase size (Figure 1a) 

that can be easily carried by a person. However, the actual 

size of the “guts” of the DMS sensor is only few millimeters, 

so the potential for further miniaturization is significant. 

In conjunction with portable computing devices such as 

the smartphone (e.g. iPhone TM or DROID TM ) technologies, 

the actual field unit may be reduced to a hand-held size in 

the near future. These units could be easily taken into an 

orchard and used for an on-site measurement by growers, 

managers, or regulators. 

An additional advantage of the DMS sensing method 

is its portability. The PCR-based assay for identification of 

HLB-associated bacteria, which is currently the method of 

choice for the HLB detection, requires sophisticated instrumentation 

and sample processing that can only be done at 

the appropriately equipped 

regional laboratory. In contrast, 

DMS measurements 

can be done on-site and 

streamlined with the use of 

dedicated equipment. 

For example, an automated 

GPS-controlled robotic 

platform carrying sensing 

unit(s) could be set up 

to scout orchard acreage for 

diseased trees and map their 

location with minimal need 

for an operator and/or laboratory 

personnel interactions. 

We have initiated DMS 

studies of trees infected with 

one of two citrus pathogens, 

Liberibacter spp. and CTV, 

using the portable DMS 

units. For the HLB studies, the infected or diseased and presumed 

healthy Hamlin orange trees located in the orchard 

at the Citrus Research and Education Center (Lake Alfred, 

FL) were visually selected by human scouts and confirmed 

to be healthy/infected by PCR. 

In order to sample a tree, leaves on a branch were placed 

in front of the DMS unit’s inlet (Figure 1b) to draw the air 

off the leaf surfaces and into the unit. The chemicals were 

pre-concentrated on a sorbent trap for a set period of time. 

After that, the trap was heated and desorbed chemicals were 

introduced into GC column followed by DMS analysis. The 

resultant GC/DMS trace reflects the total IVOC fingerprint 

for a particular tree (Figure 2). 

We have collected DMS data from infected citrus 

throughout the year to account for seasonal differences in 

VOC production by the trees. Currently, the data are being 

analyzed, and our diagnostic algorithms are being fine-tuned 

for the detection of disease-related volatile “biomarker” 

compounds. 

Data analysis and model development 

This year-round sampling period included significant 

fluctuations in weather conditions from extremely hot temperatures 

with high humidity in summer to freezing temper- 


atures with lower humidity in winter. A number of trees with 

symptoms varying from very mild to severe were included in 

the study (health status confirmed by PCR in all cases). This 

will allow us to assess feasibility of the DMS-based chemical 

sensing for early-stage asymptomatic disease detection. 

The collected data are being analyzed, and a mathematical 

model is currently being developed for the differentiation of 

HLB-sick and healthy trees based on our data. 

We ultimately seek to identify the chemical compounds 

produced by citrus trees and then link the response of our 

DMS unit to variations in the production of these particular 

compounds. To do this, we also sample citrus VOCs using 

solid phase micro extraction (SPME) and Twister TM devices, 

in parallel to the portable GC/DMS units. 

The SPME and Twister devices have a different design, 

but both operate in a similar fashion to each other – offgassed 

citrus VOCs are adsorbed onto a polymer coating 

when the collection devices are exposed to a tree leaf for a 

predetermined period of time. Upon heating, the adsorbed 

chemicals can be desorbed and introduced into laboratorybased 

traditional gas chromatography mass spectrometry 

(GC/MS) instruments. 

This lab analysis will allow us to identify differences in 

VOCs production due to pathogen infection and identify 

specific “biomarker” compounds using the MS data. An 

example of how we perform unique confirmatory chemical 

identification using MS is shown in Figure 3. 

In the final phase of our study, we are working to link the 

production of VOCs to specific gene activity in citrus plants 

that is associated with specific chemical signatures or IVOC 

biomarkers. Specific genes can be up- or down-regulated in 

response to a certain pathogen that in turn result in selected 

alterations of citrus metabolism and of the emitted VOCs 

that we can observe as off-gassed by the trees. By comparing 

healthy and infected trees it is possible to determine when 

particular genes were up- or down-regulated. Since one gene 

corresponds to a specific protein or an enzyme, it is possible 

to conceive of this as an entire network of metabolic activity 

leading to the production of certain end-product VOCs 

based on previously classified metabolic networks. 

To date, we have collected leaf samples for deep transcription 

level sequencing, and these transcriptome analyses 

will be carried out along with DMS and GC/MS experiments. 

Project Leader Dr. Cristina Davis is an Associate Professor 

in the Department of Mechanical and Aerospace Engineering, 

University of California Davis. Co-Project Leader 

Dr. Abhaya M. Dandekar is a Professor in the Department of 

Plant Sciences, UC Davis, and Co-Project Leader Dr. Oliver 

Fiehn is a Professor with the UC Davis Genome Center and 

Bioinformatics Program. Dr. Alexander Aksenov is a development 

engineer, Dr. William Cheung is a postdoctoral fellow, 

Dr. Weixiang Zhao is an associate specialist, and Dr. 

Hamzeh Bardaweel is a postdoctoral researcher, all in the 

Bioinstrumentation and BioMEDs laboratory directed by 

Prof. Davis. At the time of this work, Dr. Federico Martinelli 

was a postdoctoral fellow in the Dandekar laboratory, UC 

Davis Department of Plant Sciences. 

CRB research project reference number 5100-135. l 

Sabinene 

Fig. 3. Identification of chemical compounds from GC/MS data. The top panel shows a fragment of a typical gas 

chromatogram (GC) recording. The mass spectrum for the peak flagged on gas chromatogram is shown on the bottom 

panel. The mass spectrum corresponds to a specific terpene compound called sabinene that is commonly found in citrus. 


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COPYRIGHT © JANUARY 2012 ORO AGRI INC. • ALL RIGHTS RESERVED • TRANSFORMER AND LIQUID RIPPER ARE PROPRIETARY TRADEMARKS OF ORO AGRI

Celebrating Citrus 

Farm Show concession for Boys & Girls Club 

serves up a ‘citrus-y slaw’ and fresh-squeezed juice 

Jim Gorden 

Cabbage is an amazingly versatile 

and healthy vegetable. The use 

of cabbage in various forms is 

common in many cultures of the world. 

Here in the USA, one of its most common 

uses is in the quintessential American 

picnic green salad, coleslaw. 

I enjoy its versatility and durability 

for making green salads. I have hauled 

it on 10-day mule pack trips into the 

mountains of Baja California. There, 

I prepared cabbage salads for the trip 

participants and the cowboys/muleskinners 

of Baja who all enjoyed its 

freshness after a long day in the saddle. 

Interestingly, the cabbage maintained 

its quality with only the cooling provided 

by a moist bean sack and in spite 

of temperatures well into the 80s. 

I have prepared my citrus-y slaw 

for thousands of patrons of the Boys 

and Girls Clubs food concession at the 

World Ag Expo, aka “The Farm Show”, 

held every February in Tulare, California. 

At the inception of the food concession, 

we featured fresh navel orange 

juice. Now, we also offer a blend 

of navel and blood orange juice as well 

as fresh made lemonade. Many Farm 

Show visitors were at first put off by 

the blood orange juice, as it was new to 

them. But after a few years of its becoming 

familiar, we find people coming 

back and saying things such as “it’s really 

the Farm Show now as I’ve had my 

glass of blood orange juice”. 

About ten years ago, I started preparing 

coleslaw for the lunch plates 

served at the concession. Initially, we 

dressed the slaw with a rather traditional 

mayonnaise style dressing. I wanted 

to offer something a little different, 

featuring more citrus. Thus, I concocted 

a Meyer lemon vinaigrette dressing, 

which is a beautiful complement to the 

cabbage. We make the dressing fresh 

Bottom left: The B&GCS concession is famous for its special blend of navel and 

blood orange juice. In the background are volunteers Emily Lowry and dad, Sonny. 

Bottom right: She may be in charge, but there’s no getting out of dishwashing 

duty for Mary Gorden. Photos by Chris Brooke. 

each day with locally produced olive 

oil and Meyer lemons. 

The super citrus-y version of the 

slaw includes diced orange, tangelo, 

or mandarin tossed into the salad. The 

citrus and cabbage complement each 

other very nicely when prepared this 

way. This salad may also be varied by 

adding other ingredients to change its 

character. Toss in a handfull of bacon 

bits and a bit of hot curry into the vinaigrette 

for a hint of the Far East. Add 


some chopped cilantro for a south-ofthe-border 

effect or a little chopped 

fresh mint for a Moroccan touch. 

For “feeding the masses” at the 

Farm Show, we start each day with 

at least 100 pounds of freshly shredded 

cabbage, two cups of finely grated 

Meyer lemon zest, and three quarts of 

vinaigrette. 

But for a smaller crowd, like maybe 

six, try the following: 

Super citrus-y slaw for 6 

• ½ head of cabbage, finely shredded 

• Finely grated zest from a small to 

medium size Meyer lemon 

• Peel and dice an orange, tangelo 

or mandarin 

Meyer lemon vinaigrette dressing 

• Combine in a small jar with a tight 

lid, and shake to emulsify: 

• 3 Tablespoons Meyer lemon juice 

• 3 Tablespoons olive oil 

• 1 Tablespoon sugar 

• ½ Teaspoon salt 

The backstory … 

Based in Exeter, the Boys & Girls 

Clubs of the Sequoias (B&GCS) serves 

more than 7,000 kids a year at their afterschool 

programs at 17 sites throughout 

Tulare County. For their World Ag 

Expo fundraiser, teams of volunteers 

contribute more than 2,000 man-hours 

of effort every year in staffing the concession, 

working from 6 a.m. to 6 p.m. 

daily. 

Gorden reports that his wife, Mary, 

who serves on the B&GCS board of 

directors, “carries the bulk of the load 

for the overall planning and direction” 

of the concession while he’s more involved 

with the food prep, which includes 

making the beans and the slaw 

as well as overseeing the cooking of the 

meat and the juicing operation. They 

go through six bins of oranges, he says. 

Lemon Cove grower Jim Gorden, 

here with son Milo, is the immediate 

past chairman of the Citrus Research 

Board and continues to serve as an 

active member of the Board. 

Combine the cabbage, zest and 

diced citrus and toss with just enough 

of the dressing to coat the cabbage. 

Season to your taste with additional 

salt and pepper, and enjoy. 

Note that you can also use other 

citrus zest in salads for a different effect. 

Minneola tangelo—or for that 

matter almost any mandarin or orange—gives 

great flavor to salads. I 

use a micro-plane grater to remove 

the zest from a medium-size lemon 

with a few easy strokes. You may 

wish to adjust the acidity or sweetness 

of the vinaigrette, which you 

can do by adding or reducing the 

sugar proportion; or, if the Meyer 

lemons are too sweet as they may 

get toward spring, substitute some 

regular lemon juice. Extra vinaigrette 

may be stored in the refrigerator 

for a week or more but will 

need to warm up a bit before use as 

the oil will solidify. 

CRB stakes out new territory 

at World Ag Expo 

After years of occupying booth 

space inside Pavilion A at the 

World Ag Expo, the Citrus Research 

Board moved to an outdoor space for 

this year’s “Farm Show”, allowing the 

program to expand the exhibit. 

The new location is on a northsouth 

street just east of Pavilion B. 

The number one advantage to the 

outdoor space is that it’s large enough 

to accommodate the mobile laboratory 

that Dr. Beth Grafton-Cardwell 

and her team use in the field to train 

members of the industry and the general 

public about management of citrus 

pests. The microscopes inside the lab 

provide close-ups of insect life stages. 

Facing the mobile lab, on the opposite 

side of the “lot”, a tented area 

housed a fresh fruit display, a demonstration 

of the CPDPP’s invasive pest 

mapping website, and a demonstration 

of the Nomad hand-held data loggers 

used in the field in the Asian citrus 

psyllid trapping program. 

As for CRB’s former space in 

Pavilion A, it’s now home to the CP- 

DPP’s public education and outreach 

program on ACP and huanglongbing. 

...continued on next page 


2012 World 

Ag Expo 

Continued from p. 59 

Photo by Lynn Sanderson 

United States 

Department of Agriculture 

Asian Citrus Psyllid Cooperative Project 

California, Arizona, Baja California, and Sonora 

Animal and Plant 

Health Inspection Service 

SAN 

BENITO CO 

FRESNO CO 

TULARE CO 

INYO CO 

Navajo Co 

MONTEREY 

CO 

KINGS CO 

NV 

Mohave Co 

Coconino Co 

SAN LUIS 

OBISPO CO 

KERN CO 

SANTA 

BARBARA CO 

CA 

VENTURA CO 

LOS 

ANGELES CO 

Yavapai Co 

San Miguel Santa 

Santa 

Anacapa 

Island Rosa 

Cruz 

Island Island 

Island 

SAN 

BERNARDINO CO 

RIVERSIDE CO 

La Paz Co 

Gila Co 

Graham Co 

San Nicolas 

Island 

Santa 

Barbara 

Island 

Santa 

Catalina ORANGE CO 

Island 

SAN 

DIEGO CO 

IMPERIAL CO 

AZ 

Maricopa Co 

Pinal Co 

San 

Clemente 

Island 

Yuma Co 

Legend 

ACP_Regulatory Incidents_2011 thru Feb, 2012_CA & AZ 

!( Asian Citrus Psyllid, CA_2012 thru 3-12-12 (4,302 records) 

!( Asian Citrus Psyllid, CA_2011 (13,550 records) 

!( Asian Citrus Pysllid, AZ_2011 (3 records) 

!( Asian Citrus Psyllid, Mexico_2012 thru 3-2-12 (82 recrods) 

!( Asian Citrus Psyllid, Mexico_2011 (614 records) 

Quarantine for Asian Citrus Psyllid, CA (1/26/2012) 

Quarantine for Asian Citrus Psyllid, AZ (12/7/2009) 

USDA, APHIS, PPQ 

GIS Specialist -- California 

650 Capitol Mall, Suite 6-400 

Sacramento, CA 95814 

Coordinate-System: 

CA Teale Albers, NAD 83 

Date Printed: 3/15/2012 

Time Printed: 07:47 hrs PT 

Map of Asian citrus psyllid detections in California and neighboring portions of Arizona and Mexico through 3/12/12. 


Data Source: 

CA Dept of Food & Agric. 

AZ Dept of Agriculture 

USDA, APHIS, IS 

TeleAtlas Dynamap 

Baja 

California 

o 

Sonora 

Pima Co 

Santa 

Cruz Co 

Miles 

0 10 20 40 60 80 100 

The U.S. Department of Agriculture's Animal and Plant Health Inspection Service 

collected the data displayed for internal agency purposes only. These data may 

be used by others; however, they must be used for their original intended purpose.

Please support the Harry Scott Smith 

Biocontrol Scholarship Fund 

at UC Riverside 

A special message from 

invasive species researcher Mark Hoddle 

Invasive species are an ever-increasing problem in California agriculture, and 

obviously citrus is no exception. One tool that can be used to combat invasive 

species is biological control. The science of biological control – the use of a 

pest’s natural enemies to suppress its populations to less damaging densities – was 

pioneered in Southern California. This new discipline in entomology was in large 

part driven by the citrus industry’s need to control invasive species, especially the 

cottony cushion scale which was devastating citrus in the late 1880s. 

The phrase “biological control” was first used by Harry Scott Smith in 1919 at 

the meeting of Pacific Slope Branch of the American Association of Economic 

Entomologists at the Mission Inn in downtown Riverside. In 1923, Smith, who 

had been working on the biological control of gypsy moth with USDA, moved to 

the University of California Riverside to form the Division of Beneficial Insect 

Investigations, a unit separate and distinct from the Department of Entomology. 

Prof. Smith, affectionately known as “Prof. Harry”, went on to create and 

chair the Department of Biological Control at UCR, which offered the only 

graduate degrees in biological control in the world. He is considered the “father” 

of modern day biological control. Prof. Harry brought recognized entomological 

training in biocontrol to California for the first time, encouraging work on the 

applied and practical aspects. Under Prof. Harry’s supervision, the science of 

biological control was developed in Southern California, and, naturally, a major 

research focus was the biological control of citrus pests. 

The Harry Scott Smith Biological Control Scholarship Fund in the Entomology 

Department at UCR was started with a small gift from Prof. Harry, and regular 

fundraising is necessary to maintain and grow the fund. The sole purpose of the 

fund is to attract the brightest students to UCR to study biological control. To 

do this, awards are made annually to provide assistance to students studying 

biocontrol so they can attend conferences to present the results of their research 

or to participate in training workshops. 

With an ever-increasing number of production challenges facing the citrus 

industry, biological control is still one of the best tools available for reducing 

economic damage from invasive pests, and projects on Asian citrus psyllid and 

Diaprepes root weevil are attempting to do this. 

If you are interested in supporting the Harry Scott Smith Biological Control 

Scholarship Fund at UCR, tax deductible donations made payable to the “UC 

Foundation” can be mailed to Mark Hoddle, Department of Entomology, University 

of California, Riverside, CA 92521. More information on the Scholarship, 

past awardees, and a list of donors can be reviewed at http://biocontrol.ucr.edu/ 

hoddle/harrysmithfund.html. 

Any level of financial support you can provide for the Harry Scott Smith 

Biological Control Scholarship Fund at UCR will be greatly appreciated. 

Thank you, 

Professor Harry Scott Smith 

Mark Hoddle collecting Asian citrus psyllid 

natural enemies in the Punjab of Pakistan. 

Dr. Mark S. Hoddle 

Director, Center for Invasive Species Research 

UC Riverside 


DPR honors Sunwest Fruit with 

IPM Innovator Award 

Sunwest Fruit Company, Parlier, 

has been singled out by the California 

Department of Pesticide 

Regulation as one of four organizations 

receiving DPR’s 2011 IPM Innovator 

Awards. 

Ranch managers Greg Thonesen 

and Brian Fien accepted the honor on 

the company’s behalf at a Jan. 26 ceremony 

held at the Sacramento headquarters 

of the California Environmental 

Protection Agency. Sunwest 

President Martin Britz was in attendance 

as was his son, Brett Britz. 

The awards are presented annually 

for leadership in reducing pesticide use. 

Honored this year along with Sunwest 

were the city of Palo Alto, Gallo’s Sonoma 

Vineyards, and Marin County. 

Announcing the winners, DPR 

noted that Sunwest, a privately owned 

grower/packer/shipper of stone fruit 

and citrus, “uses a variety of innovative 

IPM practices”. 

DPR reported that the company 

“grew the first citrus and stone fruit 

certified by Protected Harvest, a nonprofit 

organization that promotes sustainable 

agricultural practices, and sold 

under Zeal, an eco-label targeting socially 

and environmentally conscious 

consumers. 

“Sunwest has eliminated the use 

of simazine, diuron and other herbicides 

known to contaminate ground 

and surface water. It allows native vegetation 

to grow between trees, which 

reduces erosion and soil compaction 

and increases organic matter in the 

soil. Other practices include modifying 

tractors and adding enclosed cabs with 

carbon air filters to reduce applicator 

exposure and provide a safer, more 

comfortable work environment. 

“The company traps and tracks 

red scale populations with global positioning 

system mapping and partnered 

with Agrian, a Fresno-based software 

firm, to develop an iPad application to 

** 35-60 Horsepower Requirement 

** 15-600 Gallon per Acre Capability 

** Maneuverable Ten ft. Long Chassis 

** Weight & Height Adjustment 

** Penetrating Spray from Twin Fans 

** Save 20-30% in Chemicals 

** Identical Spray Pattern Each Side 

** 85% Droplets are 50 Micron Size 

** 200-500 Gallon Tank 

 

 

 

 

 

 

 

 

“Heavyweight Performance! Lightweight Price!” 

Brian Fien and Greg Thonesen of Sunwest 

Fruit Company. Photo by Alyssa Nichols, 

courtesy of California Citrus Mutual. 

capture the data. It uses pheromone 

disruption for pests in stone fruit using 

dispensers known as puffers and 

installed bio-filters in the Tivy Creek 

watershed to filter runoff and prevent 

pesticides and other pollutants from 

entering the creek. “ 

DPR reports that since the IPM Innovator 

Awards were initiated in 1994, 

more than 100 California organizations 

have been recognized for their efforts 

to reduce risks associated with pesticide 

use and for sharing their knowledge 

and methods with others. Nominees 

are evaluated in seven categories: 

innovation, value, effectiveness, supports 

research, organizational education, 

outreach, and leadership. l 


THE ANSWER 

What happened in California 40 years ago that still impacts 

pest management operations today (Do You Know, page 5) 

In the spring of 1972, the California Department of Agriculture 

unveiled proposed regulations “that will place persons recommending 

agricultural pest control methods under strict licensing and registration 

requirements.” 

As reported in the June 1972 issue of Citrograph, “The proposed 

regulations set up procedures for licensing by the State Director of 

Agriculture and registration with the agricultural commissioner of 

every county in which the pest control advisers operate. To get an 

agricultural pest control adviser’s license, the applicant must pass 

a comprehensive test of his knowledge of laws, regulations, safety, 

pests, pest control methods, and environmental effects of pesticides. 

“Each agricultural pest control adviser will be required to place 

all recommendations in writing and provide copies for the grower, 

dealer, and applicator...” 

A FOLLOW-UP NOTE… In our grower profile 

of John J. Gless (January/February 2012), we neglected to include 

something that obviously should have been mentioned 

and that’s his work with California Citrus Mutual. He has 

served on the CCM board of directors since 2003 and is an 

active member of their marketing committee. 

HELP WANTED 

Duarte Nursery is now hiring container 

growers specializing in citrus. 

Salary commensurate with experience, 

all levels of formal education welcome to apply. For 

more information, please contact Michael Vietti at (209) 

531-0351 or Michael@duartenursery.com. 

Successful growers like 

Mark Campbell of Willits & 

Newcomb cover their Citrus 

with Agra Tech Greenhouses. 

Agra Tech is here to help 

your crop stay healthy and 

protected from Psyllids. 

 

 

 

 

C I T R U S 

– A V O C A D O S – O L I V E S 


Friends Day 

May 4th 2012 • 9 am - 2 pm 

• Tradeshow 

• Tours 

• Presentations 

• Wine Tasting 

• Lunch 

For more information contact: 

Sara at sara@duartenursery.com 

1555 Baldwin Rd. 

Hughson, Ca. 95326 

1-800-GRAFTED

IPM practitioner Joe Barcinas with IPM researcher Joseph Morse

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