PCC January/February 2018

January/February 2018 

Managing Navel Orangeworm on 

Two Million Acres 

California Combats the Asian 

Citrus Psyllid and Huanglongbing Disease 

New Changes for the Use of 

Chlorpyrifos 

Nitrogen Fertility Management of Cool Season 

Vegetables: A Year-Round Perspective 

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PUBLICATION 

Volume 3 : Issue 1

PUBLISHER: Jason Scott 

Email: jason@jcsmarketinginc.com 

EDITOR: Kathy Coatney 

Email: article@jcsmarketinginc.com 

PRODUCTION: design@jcsmarketinginc.com 

Phone: 559.352.4456 

Fax: 559.472.3113 

Web: www.progressivecrop.com 

CONTRIBUTING WRITERS & INDUSTRY SUPPORT 

Lisa Blecker 

Pesticide Safety Education 

Program Coordinator with the 

UC Statewide Integrated Pest 

Management Program 

Greg W. Douhan 

Area Citrus Advisor for Tulare, 

Fresno, and Madera Counties, 

UCCE, Tulare 

Ben Faber 

Subtropical Crop Advisor for 

Ventura and Santa Barbara 

Counties, UCCE, Ventura 

Matthew Fidelibus 

Department of Viticulture and 

Enology at UC Davis 

Peter Goodell 

UCCE Advisor Emeritus, IPM 

Beth Grafton-Cardwell 

IPM Specialist and Research 

Entomologist, UC and Director 

of Lindcove Research and 

Extension Center, Exeter 

UC Cooperative Extension Advisory Board 

Kevin Day 

County Director and 

UCCE Pomology Farm 

Advisor, Tulare/Kings County 

David Doll 

UCCE Farm Advisor, Merced 

County 

Dr. Brent Holtz 

County Director and UCCE 

Pomology Farm Advisor, San 

Joaquin County 

Craig E. Kallsen 

Fruit and Nut Crop Advisor 

for Kern County, UCCE, 

Bakersfield 

Sonia Rios 

Subtropical Crop Advisor 

for Riverside and San Diego 

Counties, UCCE, Moreno 

Valley 

Samuel Sandoval Solis 

Assistant Professor at UC Davis, 

and UCCE Specialist in Water 

Resources 

Richard Smith 

Vegetable Crops Farm 

Advisor, Monterey County 

Emily J. Symmes 

Sacramento Valley Area IPM 

Advisor, UC Statewide IPM 

Program and UCCE 

Amy Wolfe 

MPPA, CFRE 

President and CEO, AgSafe 

George Zhuang 

UCCE at Fresno County 

Steven Koike 

UCCE Plant Pathology 

Farm Advisor, Monterey & 

Santa Cruz Counties 

Emily J. Symmes 

UCCE IPM Advisor, 

Sacramento Valley 

Kris Tollerup 

UCCE Integrated Pest 

Management Advisor, 

Parlier, CA 

The articles, research, industry updates, company profiles, and 

advertisements in this publication are the professional opinions 

of writers and advertisers. Progressive Crop Consultant does 

not assume any responsibility for the opinions given in the 

publication. 

4 

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12 

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IN THIS ISSUE 

Managing Navel Orangeworm on 

Two Million Acres 

Keeping Pesticides out of Water – 

An Extension Program 

New Changes for the Use of 

Chlorpyrifos 

California Combats the Asian 

Citrus Psyllid and Huanglongbing 

Disease 

Crop Load Management on Newly 

Planted Pinot Gris in the San 

Joaquin Valley 

The IPM Tool Box – Maintaining 

Diversity and Investment 

Nitrogen Fertility Management of 

Cool Season Vegetables: 

A Year-Round Perspective 

2 Progressive Crop Consultant January/February 2018

4 

UPCOMING EVENTS: 

North Valley Nut Conference 

January 31, 2018 | 7:00AM - 3:00PM - wcngg.com 

Silver Dollar Fairgrounds 

2357 Fair St, Chico, CA 95928 

Join us as we bring together Almond and Walnut growers 

in the Northern California region. This conference will offer 

education, networking, and free industry lunch. 

12 

24 

14 

28 

20 


www.progressivecrop.com 

3

Managing Navel 

Orangeworm on Two 

Million Acres 

By Emily J. Symmes | Sacramento Valley Area IPM Advisor, UC Statewide IPM 

Program and Cooperative Extension 

Navel orangeworm (NOW) populations 

exploded in 2017, costing 

growers tens of millions of dollars in 

reduced quality and lost yields. In a year 

where double-digit damage estimates 

from nut processors were not uncommon, 

the question heading into the coming 

growing season (and future seasons 

beyond 2018)—how do we limit damage 

from this pest? Is our current arsenal 

of integrated pest management (IPM) 

tactics enough to keep damage in the 

desired one to two percent range given 

the two million (plus) acres of commercial 

nut crop habitat in California (not to 

mention the myriad other crop and noncrop 

plants that play host to NOW)? 

This article covers the “tried-and-true” 

strategies, as well as where we need to 

head in the future of NOW management 

to ensure clean, safe, and profitable nut 

crops for years to come. 

A four-pronged approach to NOW 

management in nut crops has been 

suggested for years based on University 

research and field success stories. These 

include: sanitation, minimizing damage 

by other sources, timely (early) harvest 

to avoid late generation flights, and 

insecticide treatments as deemed necessary 

by monitoring pest activity and 

crop phenology. 

Sanitation 

By now you have certainly received 

the message—SANITIZE! This single activity 

is the absolute backbone of all pest 

management targeting NOW, no matter 

the nut crop. This practice results in direct 

destruction of overwintering worms, 

as well as destruction of spring habitat 

for any part of the population that 

survived the winter (those remaining 

in the orchard or those migrating into 

the orchard from external 

sources outside of your 

control). In many 

cases, it’s simply 

not enough to 

get nuts on the 

ground, but 

additional 

destruction 

of the nuts 

is required 

in order to 

achieve maximum 

reduction 

in emergence, 

population build-up, 

and damage (NOW will lay eggs on and 

develop in ground mummies if that is all 

that is available). 

Plenty of research summarizes the 

effectiveness of sanitation practices (e.g., 

Higbee and Siegel 2009, California Agriculture, 

Volume 63). Research has also 

suggested that females prefer to oviposit 

(lay eggs) on nuts previously damaged 

by NOW, and that development rate and 

survival success are both also positively 

correlated with previous kernel damage 

(Hamby and Zalom 2013, Journal of 

Economic Entomology, Volume 106). 

Therefore, all mummies are not created 

equal. Clearly, a mummy with live 

overwintering worm(s) is a 

bigger threat in the coming 

season than one without 

live worm(s). Live moth- 

(s) will emerge from 

these mummies and 

give rise to subsequent 

generations, which will 

ultimately target the 

Adult navel orangeworm. 

Credit: University of California 

Statewide IPM Program. 


Navel orangeworm eggs on an almond mummy. 

Credit: Jhalendra Rijal. 

in-season crop at/after hull split. But, even a mummy that no longer 

contains a live worm come late winter-early spring, but had 

previous NOW damage, may be a more desirable and hospitable 

“home” for oviposition and early generation development (leading 

to greater population development as the season progresses). 

Encourage your growers not to underestimate the value of 

sanitation, particularly in a year with very high potential carry 

over based on elevated damage in the 2017 harvest. Sanitation to 

the University-standard guidelines (average 0.2 mummies/tree 

southern San Joaquin Valley; average 2 mummies/tree northern 

San Joaquin Valley and Sacramento Valley) may not possible 

due to prohibitive costs, labor shortages, or inclement weather 

limiting orchard access (as was the case this past season). In these 

cases, it may become necessary to target sanitation efforts to get 

the most bang-for-the-buck (i.e., emphasize mummy reduction in 

blocks with the biggest NOW threat). 

Send us a sample of your mummies 

and we will help you find the answer! 

For more information 

visit our website at integralaginc.com 

or give us a call at 1.530.809.4249 

Crack-Out 

How to determine which areas these are? This can be 

determined based on block-specific estimates of a combi- 

Continued on Page 6 



5

Continued from Page 5 

nation of total mummy load, mummy 

infestation, and kernel damage. Mummy 

samples can be collected and crackedout 

after harvest and before sanitation 

efforts (ideally, post-sanitation there 

will be too few mummies left to collect a 

meaningful sample in a timely manner). 

Note the percent infestation and kernel 

damage as well as total number of viable 

worms (multiple NOW can emerge from 

a single mummy). Extrapolations can 

then be made based on these data combined 

with estimates of total mummy 

load in the block, indicating where the 

highest potential NOW pressure may be 

in the coming season. There are newly 

available mummy “crack-out” services 

Navel orangeworm larva and damage in 

walnut. Credit: University of California 


to assist in evaluating these parameters 

and how to best use the information for 

site-specific orchard management strategies 

targeting NOW. 

What information can be used to 

facilitate “decision-support”? In other 

words, is treatment necessary? If so, 

when are the ideal timing(s)? These are 

million-dollar questions, and no single 

piece of information (to date) can 

provide fail-safe treatment guidelines. In 

fact, correlating in-season arthropod (insect 

and mite) population estimates with 

ultimate harvest damage is the IPM holy 

grail—and one that largely continues to 

elude researchers. A recent retrospective 

analysis of six years of data (Rosenheim 

et al. 2017, Journal of Economic Entomology, 

Volume 110) suggested that 

population NOW estimates taken just 

prior to harvest were the best predictors 

of almond damage. However, as practitioners 

are aware, treatment decisions 

are needed earlier than this for NOW in 

California’s nut crop systems. 

Monitoring and 

Risk-Assessment 

Let not your heart be troubled, however. 

We do have a number of different 

monitoring and risk-assessment methods, 

that when taken as a whole, may 

provide a basis for decision-support 

and treatment recommendations. These 

include using egg traps for establishing 

population biofixes that mark the onset 

of activity of each generation, pheromone 

traps for tracking adult male flight 

activity and relative population abundance, 

kairomone (ground almond-pistachio 

bait bag) traps for tracking adult 

female flight activity 

and relative population 

abundance, degree-day 

models for predicting 

population cycles, crop 

phenology landmarks 

(e.g., hull split) and 

Navel orangeworm damage in almond. Credit: University of California 


their coincidence with pest activity, 

estimates of population pressure based 

on mummy evaluation (as described 

above), previous season harvest damage, 

proximity to external sources of infestation, 

environmental conditions, and the 

list goes on. 

Refining these puzzle pieces into a 

useable risk-assessment model that can 

be validated across cropping systems, 

geographic regions, and a multitude of 

other variables, will require an ecoinformatics 

(“big data”) approach. Luckily, we 

are entering (in fact, already in) an era of 

crop management where technology is 

increasingly affording researchers, crop 

advisors, growers, and land managers 

improved methods of record-keeping, 

data analysis, and anonymized sharing 

of information in order to work toward 

solving these difficult crop production 

issues. 

Future of IPM 

Management 

What about the future of integrated 

pest management for NOW? Mating disruption 

is becoming more widely adopted 

among nut crop producers in California 

(particularly almond and pistachio). 

With the increased nut crop footprint in 

California and the ubiquitous and unrelenting 

nature of a pest like NOW, this 

may well become the 5th pillar in our 

basic NOW management strategy in the 

near future (in addition to the four noted 

early in this article). Multiple products 

are now available from a number of 

companies, which provides options for 

use and adoption, and may drive costs 

down due to increased market competi- 

tion. Population 

reduction using 

mass trapping, 

or attract-andkill, 

approaches 

are possible. The 

pistachio industry 

has invested in 

sterile insect technology, 

in which 

moths are irradiated, 

rendering 

them sterile, and 

then released into 

the “wild-type” 

population in 

order to reduce 

the number of 

successful matings. 

This technique has been successfully 

used for other serious crop pests in the 

United States, including pink bollworm 

and screwworm, and releases for medfly 

in areas of detection are ongoing in 

California. Widespread adoption of the 

“tried-and-true” management methods, 

as well as these novel approaches (and 

others, as they become available and are 

validated), will be needed for long term 

and effective management of NOW. 

Comments about this article? We want 

to hear from you. Feel free to email us at 

article@jcsmarketinginc.com 


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7

KEEPING PESTICIDES OUT OF WATER 

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Program 

By Lisa Blecker | Pesticide Safety Education Program Coordinator with the UC Statewide 

Integrated Pest Management Program 

Dr. Samuel Sandoval Solis | Assistant Professor at UC Davis, and Cooperative Extension 

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all of which require water and many 

of which require pesticide applications. 

Some of these pesticides end up in our 

water system, causing profound impacts. 

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and by implementing good application 

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put together an educational and extension 

program for pest control advisers 

(advisers) and pesticide applicators 

(applicators) to teach them how to keep 

pesticides out of water. This project has 

been led by Lisa Blecker (Lisa), Pesticide 

Safety Education Program Coordinator 

with the UC Statewide Integrated Pest 

Management Program and Dr. Samuel 

Sandoval Solis (Sam), Assistant Professor 

at UC Davis, and Cooperative Extension 

Specialist in Water Resources. Both Lisa 

and Sam deliver the content in English 

and Spanish. The project consists of 

three modules: the climate of California, 

the water cycle, and pesticide characteristics 

and applicator practices. 

Climate and Topographic 

Features of California 

First, the climate and topographic 

features of California are described, so 

advisers and applicators have a clear 

understanding of what the main climatic 

and landscape processes that can affect 

their professional practice are. They are 

introduced to concept of atmospheric 

rivers, which are high intensity and low 

duration (two or three days) rainfall 

events that account for 65 percent of 

the annual precipitation in the state of 

California. 

Headwaters 

aquifers, which are large, underground 

deposits of water. This explanation of 

the water cycle is done using a physical 

aquifer model where advisers and 

applicators can see with their own eyes 

the different pathways and processes 

that water can take. This is a hands-on 

experience where all these concepts are 

not only explained but experienced. By 

the end of this section, they have a clear 

understanding of water movement in the 

landscape, so they can apply this knowledge 

to preventing pesticides (or any 

other contaminant) from reaching and 

contaminating any water body (creeks, 

rivers, aquifers, or soil moisture). A 

series of videos that show this approach 

can be seen in the following webpage. 

Runoff 

Third, the specific characteristics that 

increase the likelihood that a pesticide 

will contaminate water through leaching 

Both leaching and runoff are more likely 

to happen with persistent pesticides— 

those with a long half life. Persistent 

pesticides are not easily degraded and remain 

in the soil for long periods of time. 

The longer a pesticide is in the environment, 

the more likely it is to become 

a pollutant. A practice recommended 

to advisers and applicators is to look at 

the weather forecast and to schedule 

pesticide applications so they do not 

occur before rainfall or irrigation events. 

In addition, they are recommended to 

not make any pesticide management 

within 100 feet of a well, because if a spill 

occurs, it can contaminate directly the 

aquifer. 

This outreach and education program 

shows the main principles of the water 

cycle, how water moves into the natural 

and agricultural environment, and how 

to prevent pesticides from reaching any 

water bodies. The overall goal is not to 

Second, they are introduced to 

water cycle and how water moves in the 

headwaters and the river valleys. In the 

headwaters, because there is a shallow 

soil layer on top of rock, precipitation 

can fall onto the land, infiltrate into the 

soil and be stored as soil moisture. Later 

it can be taken up by the plants through 

evapotranspiration or end up in rivers 

by traveling through the soil and into 

the creeks as subsurface flow. If the soil 

is already saturated, then water may flow 

directly into the creeks as surface runoff 

because water was not able to infiltrate 

into the soil layer. Alternatively, precipitation 

can be stored on the soil surface if 

it falls as snow, which later will be melted 

and may follow either of the previous 

two paths. In contrast, in river valleys, 

the soil layer is usually on top of deeper 

alluvial soil layer (sands, gravels and fine 

material), thus water can move the same 

way as previous pathways described. 

It can also infiltrate further down into 

underlying soil layers and be stored in 

Photo courtesy of Sarah Risorto and the Integrate Pest Management Program of the University of 

California, Agriculture and Natural Resources. 

or runoff are explained. These pesticide 

characteristics are water solubility 

(measured in mg/L), soil adsorption 

(measured in Koc), and persistence 

(measured in half-life). If a pesticide 

is soluble, then it will move as water 

moves. For instance, if a water soluble 

pesticide is soil-applied ahead of a heavy 

rainfall event, the pesticide will move 

with soil water and end up in aquifers 

or rivers. A similar effect can happen 

with over-irrigation. Some pesticides can 

be less soluble, or not soluble at all, but 

adsorb, or bind, easily to the soil. In this 

case, when a rainfall (or over-irrigation) 

event occur, precipitation (or over-irrigation) 

can cause surface runoff. Surface 

runoff not only carries water but also 

sediment with pesticides bound to it, 

thus, contaminating rivers and creeks. 

teach them a recipe for every pesticide 

and agricultural landscape, but to teach 

them the main principles, so they can 

apply them according to the specific 

conditions that they are dealing with day 

to day. Because this program is taught in 

English and Spanish languages, it has a 

deep impact in the agricultural community 

because it has reached different 

audiences. For further information related 

with this program feel free to contact 

Lisa Blecker (lblecker@ucanr.edu ) and/ 

or Dr. Samuel Sandoval Solis (samsandoval@ucdavis.edu). 





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11

New Changes for the 

Use of Chlorpyrifos 

By Amy Wolfe | MPPA, CFRE 

President and CEO, AgSafe 

This past April, the California Department 

of Pesticide Regulations 

(DPR) and California Environmental 

Protection Agency (CalEPA) conducted 

a risk assessment on the commonly used 

pesticide chlorpyrifos. The assessment 

revealed several potential unacceptable 

exposures that have led DPR to draft 

recommended permits conditions to 

accompany county pesticide permits. 

Lorsban is a product that contains the 

active ingredient chlorpyrifos that most 

growers would recognize. Photo courtesy 

of Scientific America.com 

Chlorpyrifos is commonly used on 

nut orchards and alfalfa and has been 

an insect mitigation tool for growers for 

the last fifty years. Now, DPR scientists 

believe chlorpyrifos may pose a public 

health risk as a toxic air contaminant 

based on its assessment of the latest 

studies in the scientific community. As 

chlorpyrifos continues to go through the 

review process, DPR has issued recommended 

permit conditions for its use. 

In addition to complying with the 

pesticide label, which is the law, county 

agricultural commissioners’ (CAC) 

offices have the authority to issue permit 

conditions with a pesticide permit. 

CACs are given this authority to mitigate 

hazards that may be specific to the farming 

in their county. In some instances, 

DPR issues recommended permit conditions 

while they finalize regulatory language. 

In the case of chlorpyrifos, DPR 

has now issued recommended permit 

conditions and is conducting training 

sessions for CAC pesticide inspectors on 

the conditions. According to DPR, most 

counties, especially in the Central Valley 

where chlorpyrifos use is prevalent, 

are adopting the recommended permit 

conditions. 

All of this begs the question, what 

does the recommended permit conditions 

outline? For ease of explanation 

let’s break the conditions into sections, 

starting with definitions. 

Definitions: 

Application Block—A field or portion 

of a field treated in a 24-hour period 

that typically is identified by visible indicators, 

maps or other tangible means. 

The perimeter of the application block 

is the border connecting the outermost 

edges of the total area treated. Essentially, 

it is the field in which you intend to 

apply chlorpyrifos. 

Sensitive Site—As described by 

labels, sensitive sites are areas frequented 

by non-occupational bystanders 

(especially children). These include 

residential lawns, pedestrian sidewalks, 

outdoor recreational areas such as school 

grounds, athletic fields, parks, and all 

property associated with buildings 

occupied by humans for residential or 

commercial purposes. Sensitive sites 

include homes, farmworker housing, 

or other residential buildings, schools, 

daycare centers, nursing homes, and 

hospitals. Non-residential agricultural 

buildings, including barns, livestock 

facilities, and sheds are not included in 

the prohibition. 

Setback Distance—Distance in feet 

that must separate sensitive sites from 

the application block. The distance must 

extend outward from the perimeter of 

the sensitive site to the perimeter of the 

application block. Setback distances 

must be established for chlorpyrifos 

applications near sensitive sites. 

Application Method 

Restrictions: 

1. All applications must take place with 

a minimum wind speed of three 

miles per hour (mph) and not more 

than 10 mph as measured at a height 

of four feet above the ground. 

2. Airblast applications: 

a. Spray the two outside crop rows 

from the outside in, directing the 

spray into the treatment area and 

shutting off nozzles on the side 

of the sprayer away from the 

treatment area. 

b. Shut off top nozzles when 

treating smaller trees, vines or 


ushes to minimize spray 

movement above the canopy. 

3. Chemigation applications: 

a. The permittee or permittee’s 

authorized representative, who is 

knowledgeable of the irrigation 

system, must be present at the 

treatment site during the 

application and must be trained 

as a pesticide handler. 

4. Granular applications: 

a. Incorporate or clean-up granules 

that are spilled during loading 

or are visible on the soil surface 

in turn areas. 

Determining application rate— 

Converting liquid volume to lbs 

AI/ac: 

The active ingredient (AI) application 

rate determines the setback distance and 

is expressed as pounds of 

active ingredient per acre (lbs 

AI/ac). Liquid product labels 

usually have the application 

rate as pints or quarts of 

product per acre. To determine 

lbs AI/ac, the volume 

of product applied needs to 

be converted to pounds of active 

ingredient based on the 

amount of chlorpyrifos active 

ingredient in the product. 

Determining application rate— 

Converting row feet rate to lbs 

AI/ac: 

Setback distances are for a broadcast 

application. When labels specify the 

application rate as fluid 

ounces per 1000 feet of 

row or 100 feet of row, 

the “broadcast equivalent 

application rate” 

is the rate of active 

ingredient (lbs AI/ 

ac) within the entire 

application block. The 

“broadcast equivalent 

application rate” 

must be calculated to 

determine the setback 

distance. 

For more information 

on how to do 

the math to calculate 

setback, visit: http:// 

www.cdpr.ca.gov/docs/ 

enforce/compend/ 

vol_3/append_o.pdf 

Setback distances: 

1. A setback distance must be established 

for every chlorpyrifos application 

near a sensitive site. The setback 

distance must extend outward from 

the perimeter of the sensitive site 

to the perimeter of the application 

block. 

a. DPR has tables that delineate the 

distance of setback required per 

application—distance ranges 

from 150 feet to 500 feet. 

2. The CAC may use the setback 

distances in the table below if 

non-occupational bystanders will 

not occupy the sensitive site anytime 

during the application and for one 

(1) hour after the end of the 

application. 

Application Method 

Unoccupied Sensitive Site 

Setback Distance (feet) 

Ground Boom 25 

Sprinkler Chemigation 50 

Airblast 50 

Aerial 150 150 

3. To ensure sensitive sites are not 

occupied anytime during the 

application and for one (1) hour 

after the application, the CAC must 

include additional permit 

conditions, such as written vacating 

The map illustrates the areas in California where chlorpyrifos 

is used the most–the Central Valley and the Coast. The 

map is courtesy of California Environmental Health Tracking 

Program.” Map is courtesy of California Environmental Health 

Tracking Program. 

agreements for sites that could 

trigger the occupied sensitive site 

setbacks, posting the occupied 

sensitive site setback distance, or 

observation and/or monitoring 

at the setback perimeter during the 

application and for one (1) hour 

after the application. 

With all of the new application 

requirements it is important to mention 

that chlorpyrifos is an organophosphate 

that already has additional requirements 

under Title 3, Section 6728. The regulation 

requires medical supervision 

for employees who regularly handle 

chlorpyrifos to ensure that their cholinesterase 

values are not being compromised 

by handling pesticides containing 

chlorpyrifos. For more information regarding 

this particular requirement, visit 

http://www.cdpr.ca.gov/docs/legbills/ 

calcode/030302.htm. 

As with any change 

in pesticide requirements, 

ensure that 

employees who will be 

handling this pesticide 

are adequately trained 

on its hazards prior to 

application. While DPR 

has recommended these 

permit conditions, CACs 

have the ability to amend them per their 

county’s specific needs. Be sure to read 

all of the permit conditions that accompany 

your pesticide permit and consult 

with your local pesticide enforcement 

inspector if you have questions. 

For more information about pesticide 

safety or any worker safety, health, human 

resources, labor relations, or food 

safety issues, please visit www.agsafe.org, 

call us at (209) 526-4400 or via email at 

safeinfo@agsafe.org. 

AgSafe is a 501c3 nonprofit providing 

training, education, outreach and tools 

in the areas of safety, labor relations, 

food safety and human resources for the 

food and farming industries. Since 1991, 

AgSafe has educated nearly 75,000 employers, 

supervisors, and workers about 

these critical issues. 






13

California Combats 

the Asian Citrus Psyllid 

and Huanglongbing 

Disease 

By Greg W. Douhan | Area Citrus Advisor for Tulare, Fresno, and Madera Counties, UCCE, Tulare, CA 

Beth-Grafton-Cardwell | IPM specialist and Research Entomologist, UC and Director of Lindcove Research 

and Extension Center, Exeter, CA 

Ben Faber | Subtropical Crop Advisor for Ventura and Santa Barbara Counties, UCCE, Ventura, CA 

Sonia Rios | Subtropical Crop Advisor for Riverside and San Diego Counties, UCCE, Moreno Valley, CA 

Craig E. Kallsen | Fruit and Nut Crop Advisor for Kern County, UCCE, Bakersfield, CA 

Photo Figures 1-5 Courtesy of University of Florida Cooperative 

Extension, University of California, and anonymous sources 

Commercially grown citrus contributes 

$3.3 billion in economic activity 

and employs more than 22,000 individuals 

in California. Although many pests 

and pathogens can affect the value of 

citrus production, only a few are able 

to inflict severe damage, reduce yield, 

and/or kill citrus trees. For California 

and some other citrus producing areas, 

Huanglongbing (HLB) is the most severe 

disease issue currently that has the 

potential to impact all aspects of ‘citrus 

economics’ if it invades the commercial 

citrus production areas. The disease is 

vectored by the insect Diaphorina citri, 

referred to as the Asian citrus psyllid 

(ACP), and in North America the bacteria 

that causes the disease is Candidatus 

Liberibacter asiaticus (CLas). Once an 

infection occurs via grafting from infected 

plant material or by HLB positive 

psyllids, the bacteria will reproduce 

within the sugar conducting tissues 

(phloem) of the infected citrus plant. Initially, 

only segments of the tree will show 

symptoms, but eventually the infection 

will spread and lead to the decline and 

death of the tree. This incurable and fatal 

plant disease threatens all citrus plants 

and close relatives of citrus in the family 

Rutaceae, some of which are occasionally 

grown as ornamentals in California. 

Currently, there is no effective way to 

directly control the disease but only to 

provide various inputs that will prolong 

production. 

The first report of ACP in California 

was in 2008 and the first HLB infected 

tree was reported in 2012 from a homeowner’s 

tree found in Hacienda Heights, 

Los Angeles County. The infected tree 

was quickly destroyed via action taken 

by the California Department of Food 

and Agriculture (CDFA). Since this first 

detection, another tree in Hacienda 

Heights was identified in 2016 from a 

different property and to date there have 

been over 240 identified infected trees 

within the greater Los Angeles region 

(Orange, Los Angeles, and Riverside 

Counties). However, no HLB positive 

trees have been found in commercial 

citrus production areas in California 

thus far. Therefore, our awareness of 

this devastating disease must be in the 

forethought of everyone, including the 

general-public, who value citrus trees 

as an essential part of the fabric of the 

California landscape. 

HLB is one of the most complex 

diseases of citrus, with interactions 

among the pathogen, vector, host and 

environment. This, coupled with a long 

latent period before symptoms appear 

and the difficulty of sampling for the 

disease that has an uneven spread in the 

tree, makes identifying HLB positive 

trees challenging. There are significant 

amounts of research dollars from various 

agencies, including the Citrus Research 

Board and United States Department of 

Agriculture (USDA), to develop tools 

to identify HLB positive trees before 

the bacteria have spread throughout the 



ADVERTORIAL 

HUANGLONGBING 

The Growing Threat of Huanglongbing 

and How You Can Protect California Citrus 

The Asian citrus psyllid (ACP), a vector of 

the bacterium that causes Huanglongbing 

(HLB) disease, has been identified in 

southern California. Vigilant pest control is 

necessary to protect California citrus from 

the severe effects of HLB. 

HLB is the most devastating citrus disease 

worldwide and threatens all commercial 

citrus production. Florida has lost 72% of 

its citrus production since 2005/2006 as 

well as 119,000 acres of citrus trees and 

$674 million since the rise of ACP. In the 

U.S., 3.2 million metric tons of citrus were 

lost due to ACP. 1 

What’s at Stake for 

California Growers? 

California represents 41% of U.S. citrus 

production with 270,000 acres of citrus 

valued at $2 billion. According to California 

Citrus Mutual, 32 infected trees have been 

found in Southern California. 2 

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ahead of Huanglongbing. 

PEST 

ASIAN 

CITRUS 

PSYLLIDS 

ü ü ü ü ü 

CITRUS 

THRIPS 

RED 

SCALE 

KATYDIDS 

CITRICOLA 

SCALE 

IRAC 

GROUP** 

BLOOM 

ü 

ü 

GROUP 4 (d) 

PETAL 

FALL 

ü 

ü 

POST- 

BLOOM 

ü 

ü 

FRUIT 

GROWTH 

ü 

WINTER 

MONTHS 

GROUP 3 GROUP 4 (a) GROUP 23 GROUPS 

3 and 4 (a) 

How ACP Affects Citrus Plants 

*Suppression only. 

**Insecticide Resistance Action Committee's mode of action groups. 

The psyllid damages citrus 

directly by feeding on new leaf 

growth (fl ush). 

More importantly, the psyllid 

is a vector of the bacterium, 

Candidatus Liberibacter asiaticus 

(CLas), that causes HLB and 

transmits the bacteria into the 

phloem when it feeds on fl ush. 

HLB disease spreads from tree 

to tree when a bacteria-carrying 

psyllid fl ies to a healthy plant and 

transmits the bacteria as it feeds 

on the leaves and stems. 

The bacteria multiply in the tree’s 

phloem tissue, blocking the fl ow 

of nutrients through the plant. 

If not well managed, trees will 

eventually die within 3 to 5 years. 

Effective control of Asian citrus 

psyllid reduces the chance that a 

citrus tree will become infected 

by the bacteria and helps ensure 

a healthy, productive tree. 

Make Bayer’s proven portfolio a cornerstone of your insecticide program to help ensure tree 

protection and productivity with season-long control of ACP, as well as other key citrus pests. 

1 

USDA’s National Agricultural Statistics Service Florida Citrus Statistics (2015–2016). 

2 

https://www.cacitrusmutual.com/build-wall-strategies-stopping-acp-hlb/ 

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Leverage, ® Movento, ® and Sivanto are trademarks of Bayer. Baythroid XL is a Restricted Use Pesticide. Not all products are registered for use in all states. For product information, call toll-free 

1-866-99-BAYER (1-866-992-2937) or visit our website at www.CropScience.Bayer.us. CR1017MULTIPB022S00R0 



15

are usually not the same on either side of 

the leaves as delimitated by the main leaf 

vein. Mottling is also most frequently 

found on newly mature leaves (hardened-off), 

but often fades with leaf age. 

However, these symptoms can also be 

sometimes confused with some nutrient 

deficiencies, but most nutrient deficiencies 

will usually produce more uniform 

mottling or chlorotic symptoms (Figure 

2). Some HLB-infected leaves may also 

produce yellow veins, vein corking, 

Figure 1 Blotchy mottle symptoms on citrus leaves. 


tree and before any visual symptoms 

are present. However, until these tools 

are developed, every individual within 

the citrus community should be aware 

of what symptoms to look for. The first 

visible symptoms observed for HLB are 

asymmetrical yellowing of 

leaves which is often referred 

to as a ‘blotchy mottle’ symptom 

of the leaves (Figure 1). 

This blotchy mottle pattern is 

a random pattern of yellowing 

or chlorosis on the leaves that 

Figure 2 Uniform and even mottling symptoms due 

to nutrient deficiencies within citrus. 


or green island symptoms (Figure 3). 

Infected trees also produce fruit that unevenly 

colors and is often lopsided and is 

sour (Figure 4). Eventually the trees will 

weaken, begin to dieback and decline 

overtime. Be forewarned, that if you 

see visible symptoms, the tree has been 

infected for months if not years, and it is 

likely that nearby trees are also infected. 

So Where Did This Disease 

Originate and Why is it 

Now a Threat? 

CLas likely infected citrus through 

psyllid species transferring the bacteria 

from indigenous rutaceous plants to 

cultivated citrus in Asia. Descriptions 

of die-back of citrus in India in the 18th 

century and the observations of farmers 

in southern China in the late 1800s 

suggest that this disease has impacted 

citrus for over 100 years. Just over a 

decade ago, HLB was confirmed in the 

Americas, originally in São Paulo State, 

Brazil in 2004 and the State of Florida, 

USA in 2005. The disease spread rapidly 

in both São Paulo and Florida, causing 

significant economic losses as it has in 

Asia for many years and has since spread 

to other States in the USA. Therefore, 

Figure 3 Corking veins and green island symptoms of HLB infected citrus. 

The first line of defense against HLB 

is to keep ACP under control in Southern 

California and coastal citrus growing 

regions and continue eradication 

efforts in the San Joaquin Valley (SJV). 

However, this is a difficult scenario in 

Southern California, since the insect 

is common throughout this region. Its 

presence in residential areas hampers 

control measures because there is always 

to appear in the SJV, so growers must 

be diligent to scout their fields. For 

monitoring, two strategies are to walk 

orchards when there are new flushes of 

growth to look for the nymphal stage 

or do tap sampling for adults. When 

looking for psyllids, signs of adults, eggs, 

Figure 4 Lopsided and unevenly coloring citrus fruit. 

it is important to be on the lookout for 

the disease, which has the potential to 

spread from residential areas of Southern 

California to the commercial production 

areas throughout California. 

So, What Can Be Done to 

Curtail the Spread of This 

Disease and Vector? 

a ‘source’ of more insects to move back 

into commercial production areas. It is 

important for growers in these regions 

to treat their orchards in a coordinated 

fashion in the spring and fall with 

ACP-effective insecticides as directed by 

their Task Force or Pest Control District. 

Within the SJV, the counties of Kern and 

to a lesser extent Tulare had frequent 

finds of ACP in 2016, but a lot of effort 

went into decreasing population levels of 

the insect through pesticide applications 

and finds thus far have decreased in 

2017. However, the insect is continuing 

or nymphs producing waxy tubules can 

be identified, as well as possible damage 

on developing leaves (Figure 5, page 

18). Detailed information regarding tap 

sampling, including a video demonstration, 

can be found at the University of 

California ANR website (http://ucanr. 

edu/sites/acp/). 

Biological control tactics were also 

initiated in 2010 to help control ACP 




17


populations within residential areas, 

since spraying of pesticides was not 

easily accomplished. The parasitic wasp, 

Tamaraxia radiata, was collected by 

University of California Riverside Entomologist 

Mark Hoddle from Punjab, 

Pakistan, because it was endemic to the 

native range of ACP and was thought 

that a similar environment to California 

would make it a potential candidate to 

fight this insect. In addition to the Tamarixia 

radiata, an additional parasitoid, 

Diaphorencyrtus aligarhensis, was also 

reared and released. Both species kill the 

ACP insects through a combination of 

parasitism and host feeding. However, 

post-release monitoring in California 

has indicated that ACP parasitism by 

T. radiata is low to moderate and varies 

greatly across locations, seasons, and 

years. Moreover, success of the parasitoids 

is also reduced when ants protect 

the psyllids from natural enemies. 

Both monitoring and management of 

ACP are extremely important concepts 

to slow the threat of HLB. Eradication 

approaches should be used in areas 

where the insect is relatively rare (SJV) 

whereas growers need to continue to 

conduct periodic coordinated treatments 

Figure 5 ACP eggs on new citrus growth, adult insect, and nymphs 

producing waxy tubules. 

in areas where ACP is well-established 

(Southern and coastal California). In 

the latter case, growers need to focus 

on reducing overwintering adults and 

protecting new flushes from egg laying 

by the insect. The fall months are 

especially important as that is when the 

populations can build to high numbers. 

It should also be noted that not all 

insecticides are equally effective against 

ACP. More information can be found at 

the University of California Cooperative 

Extension (UCCE) extension website 

(http://ucanr.edu/sites/acp/) but some of 

the key points are: 

• Focus on overwintering adults and 

protecting new flush 

• Broad spectrum, long residual insecticides 

are especially important in 

the fall when ACP populations grow 

fast 

• Rotate between chemistries to avoid 

selecting for resistance 

• Use selective insecticides for the 

spring-summer treatments to allow 

natural enemies to survive and assist 

with control 

• Be aware of Maximum Residue Limits 

to ensure export 

Weather conditions may also influence 

the spread of ACP in California, 

especially in the SJV where more than 

65 percent of the California citrus is 

produced. The SJV often has cold winters 

followed by hot dry summers that 

are not as conducive to support large 

populations 

of the vector. 

Similarly, the 

heat of the 

Coachella 

and Imperial 

valleys 

suppresses 

psyllids. Hot, 

dry summers 

also suppress 

the bacteria. 

In the SJV, 

growers use 

ACP-effective 

insecticides 

to 

control citrus 

thrips, katydids, 

citricola 

scale and 

Fuller rose 

beetle and 

these treatments 

help to keep ACP populations 

low. However, in-spite of this, ACP is expected 

to continue to spread in the SJV 

and the disease will appear eventually. In 

Southern inland and coastal California, 

ACP populations flourish. Environmental 

conditions and flushing host plants 

easily support nymphal development, 

thus the climate in these areas promote 

ACP. 

What Does the Future 

Hold for California 

Regarding ACP/HLB? 

On a positive note, there are some 

factors that may help limit the spread of 

HLB in California compared to Florida. 

The vector (ACP) thrives on young 

vegetative shoots. In Florida, there are 

constant flushes of newly developing 

tissues for the vector to continually 

develop year-round. In contrast, in California 

there are normally only two flush 

periods for most mature citrus, one in 

the spring that is always prominent and 

another in the fall that is not as prominent 

depending on the weather. The 

exception is coastal lemons that have 

continuous flushes that pose a significant 

challenge to deal with ACP/HLB, 

especially since residential and growing 

areas are more adjacent compared to 

other growing regions. Florida growers 

did not control ACP populations 

because they did not realize how severe 

HLB would be. In contrast, the California 

Department of Agriculture (CDFA) 

has been monitoring ACP in California 

since 2008, sampling citrus and ACP 

for HLB around the state, setting up 

quarantine areas based on the findings, 

and have been working with Californians 

to inform them of the spread of 

the pest and disease. This program is 

funded by California citrus growers via 

the Citrus Pest and Disease Prevention 

Program (CPDPP). The grower/packer/ 

nursery community as represented by 

the CPDPP in collaboration with various 

organizations including CDFA, USDA, 

University of California, the Citrus Research 

Board, California Citrus Mutual, 

Pest Control Districts, Task Forces and 

Pest Control Advisors have been at work 

to recommend coordinated spray programs 

to control ACP populations, assist 

with tree removal, conduct outreach 

programs, support research and develop 

recommendations for HLB management 

for the industry going forward. 







19

Crop load management on 

newly planted Pinot gris in the 

San Joaquin Valley 

By George Zhuang | University of California Cooperative Extension at Fresno County 

Matthew Fidelibus | Department of Viticulture and Enology at UC Davis 

Most (65 percent) of the total land 

area in California planted to Pinot 

gris is in the San Joaquin Valley (including 

crush district 11, 12, 13, and 14), and 

those vineyards produce > 80 percent 

of total amount of Pinot gris crushed in 

the state. In Fresno County, plantings of 

Pinot gris increased by 20 percent (from 

1803 acres to 2180 acres) from 2015 to 

2016. Growers in the southern SJV receive 

an average gross return of $448.98 

per ton for Pinot gris (California Grape 

Acreage Report and California Grape 

Crush Report 2016). The high demand 

has prompted wine growers and winery 

personnel to focus on maximizing the 

production of good quality Pinot gris 

under the SJV’s warm climate. 

In Fresno County, many current 

Pinot gris plantings have been trained to 

Figure 1 Left: control in 2016; Right: 0 cluster per shoot in 2016 


quadrilateral cordons and spur pruned 

in an attempt to maximize vine yield 

potential. Moreover, many growers are 

striving to achieve the earliest possible 

financial returns by completing trunk, 

and even cordon, training in the first 

year after planting. However, this is 

difficult with Pinot gris, a variety having 

relatively low vigor, and an excessively 

aggressive approach could lead to 

overcropping, which may have long term 

negative consequences for the vines and 

ultimately limit their productivity over 

time. 

PISTACHIOS 

ALMONDS 

WALNUTS 

Figure 2 Top: control in 2016; Bottom: 0 cluster per 

shoot in 2016 

In order to provide a guideline for 

crop load of newly planted Pinot gris in 

the SJV, a field study in a commercial 

vineyard in western Fresno county was 

initiated in April, 2016. The vineyard 

was planted in February, 2015 with 

dormant bench grafted vines of Pinot 

gris (FPS clone 04) grafted on Freedom 

rootstocks. Vines were trained to quadrilateral 

cordons that were supported by 

trellises with 18-inch wide cross arms, 54 

inches above the ground. The vineyard 

was planted with row spacing of 11 feet 

and vine spacing of 5 feet with trunk and 

cordon training completed in 2015. Four 

levels of cluster thinning were applied in 

April, 2016, before bloom when shoots 

were approximately 12 inches long. Clusters 

were clipped off of shoots, or not, 

to achieve four different levels of crop 

load; 0 cluster per shoot (0), 

1 cluster per 2 shoots (1/2), 1 

cluster per shoot (1), and nonthinned 

as control (Figure 

1, page 20). No further crop 

load adjustments were made 

thereafter, but vine growth, 

yield, and berry compositions 

data were collected annually to 

determine the initial and subsequent 

effects that cropload 

adjustment in the first fruiting 

year may have over the course 

of the first three seasons. All 

vines were subjected to the 

same irrigation, fertilization, 

and pest control practices as 

deemed fit by the grower. 

Differences in canopy 

size were observed by veraison 

2016, with non-thinned 

vines having the smallest 

canopies, whereas defruited 

vines (0 clusters per shoot) 


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21 

5/11/17 4:17 PM

Table 1 Impact of cluster thinning of 2016 on yield components in 2016 and 2017. 

Year 

2016 

2017 

Treatment of 

2016 

Cluster 

number/vine 

Yield/acre 

(ton) 

Cluster wt (g) 

Pruning wt 

(kg/vine) 

0 cluster/shoot NA NA NA 1.18 c NA 

1 cluster/2 shoots 55.9 a a 5.0 a 124 a 0.75 a 8.3 a 

1 cluster/shoot 84. 6 b 6.6 ab 98 b 0.52 b 16.1 b 

Control 113. 2 c 7.0 b 78 c 0.46 b 19.9 c 

0 cluster/shoot 224 a 16.6 ab 84.6 NA NA 

1 cluster/2 shoots 186 b 19.0 a 116.2 NA NA 

1 cluster/shoot 162 b 13.9 b 98.3 NA NA 

Control 169 b 13.3 b 90 NA NA 

Yield/pruning 

wt (kg/kg) 

a 

values with different letter designation represent significant mean separation according to Tukey-Kramer significant 

different test at p ≤ 0.05. 


had amassed a much larger canopy by 

then (Figure 2, page 21). In 2016, nonthinned 

vines had greater yields than 

vines that were thinned to one cluster 

per two shoots, and vines that were 

thinned to one cluster per shoot yielded 

similarly to non-thinned vines or vines 

thinned to one cluster per two shoots; 

defruited vines, of course, had no yield 

in 2016 (Table 1). Cluster thinning stimulated 

greater fruit set and bigger berry 

size as evidenced by thinned vines having 

more berries per cluster and bigger 

berry size than non-thinned vines (Table 

2). Cluster thinning also affected berry 

compositions, with berries from vines 

thinned to one cluster per two shoots 

having higher Total Soluble Solids (TSS) 

(approximately 2 Brix) at harvest than 

fruit from non-thinned vines (Table 2). 

Thinning did not affect pH or titratable 

acidity (TA) though thinned vines had 

slightly higher volatile acidity, indicating 

slightly greater bunch rot incidence, 

probably due to tighter clusters resulting 

from increased berry set and berry size. 

The delayed ripening and poor canopy 

growth suggest that non-thinned Pinot 

gris vines were overcropped in 2016 

(Figure 2 (page 21) and 3). Non-thinned 

Table 2 Impact of cluster thinning of 2016 on berry compositions in 2016 and 2017. 

Year 

2016 

2017 

Treatment of 

2016 

Berry number/ 

cluster 

Berry wt 

(g) 

TSS (Brix) a pH TA (g/L) VA (g/L) b 

0 cluster/shoot NA NA NA NA NA NA 

1 cluster/2 shoots 99 a c 1.06 a 23.6 a 3.5 7.5 0.02 a 

1 cluster/shoot 98 a 0.93 b 22.8 ab 3.5 7.1 0.02 ab 

Control 75 b 0.86 c 21.6 b 3.4 7.2 0.01 b 

0 cluster/shoot 75 1.06 21.9 3.5 5.9 0.01 

1 cluster/2 shoots 102 1.06 22.8 3.5 5.8 0.01 

1 cluster/shoot 84 1.08 22 3.5 5.8 0.01 

Control 75 1.12 23.3 3.5 5.8 0.01 

a 

the commercial target of TSS for Pinot gris is 22 Brix 

b 

volatile acidity requirement from the wineries < 0.16 g/L 

c 

values with different letter designation represent significant mean separation according to Tukey-Kramer significant 

different test at p ≤ 0.05. 


Table 3 Summary of yield and Ravaz Index of 2016 and 2017. 

Year 2016 2017 Sum 

Treatment Yield (t/acre) Ravaz Index Yield (t/acre) Ravaz Index Yield (t/acre) 

(kg/kg) 

(kg/kg) 

0 cluster/shoot 0 NA 16.6 NA 16.6 

1 cluster/2 shoots 5 8.3 19 NA 24.0 

1 cluster/shoot 6.6 16.1 13.9 NA 20.5 

Control 7 19.9 13.3 NA 20.3 

Figure 3 Weekly TSS (Brix) accumulation starting at 

the onset of veraison in 2016 with the means represented 

from one cluster per two shoots (1/2), one cluster 

per shoot (1) and non-thinned (control). 

Figure 4 Total soluble solids (Brix) decreased as Ravaz index 

increased beyond 10, and the vines became increasingly overcropped 

in 2016. Ravaz Index 10 

may indicated overcropping, 

whereas Ravaz index 10 may also be a reasonable 

threshold for these young vines. 

Vines with a Ravaz Index >10 

in 2016 had the least amount 

of berry TSS at the harvest of 

2016 and the lowest yields in 

2017 (Table 1 and Table 2, page 

22). Specifically, a higher Ravaz 

Index (>10) in 2016 resulted 

in less amount of berry TSS in 

2016 and less yield in 2017 (Figure 4 

and Figure 5). Thus, overcropping the 

first year, Ravaz Index >10, may inhibit 

TSS accumulation in the current 

growing season, and also limit yield 

the following season. 

Thus, newly planted Pinot gris on 

quadrilateral cordons might benefit 

from cluster thinning, e.g., one cluster 

per two shoots at the second leaf, in 

order to achieve a Ravaz Index ≤10 

which may help to achieve long-term 

yield and economic sustainability for 

the newly planted vines in the SJV. 


to hear from you. Feel free to email us 

at article@jcsmarketinginc.com 

Figure 5 Vines with a Ravaz Index >10 in 2016 

had lower yields in 2017, with yield decreasing 

as Ravaz index increased. Ravaz Index

The IPM Tool Box – 

MAINTAINING DIVERSITY 

AND INVESTMENT 

By Peter Goodell | UCCE Advisor Emeritus, IPM 

Integrated Pest Management (IPM) 

is a well-used term that describes 

many things to many people. Since IPM 

addresses the complexity of the system, 

its parts are usually described rather 

than its whole. Making this complex 

paradigm understood among its practitioners, 

the academic and regulatory 

communities and the public is important 

in communicating the value, strengths, 

and progress in managing pests. 

Certainly, one aspect of IPM discussion 

is the utilization of multiple 

management (and control) approaches. 

While integrating both across practices 

and pests, the conversation usually 

settles on a single pest and management 

issue. 

For example, when a new pest 

threatens a cropping system or an 

indigenous pest becomes out of balance 

with its environment, affected industries 

often request emergency exemptions 

for pesticide use outside the established 

registered label. Section 18 requests are a 

common example. 

When making arguments in these situations 

for additional “tools” to control 

pests are often cited as the critical need 

to avoid extraordinary economic losses. 

The analogy of IPM practices as “tools” 

and that there is a collection in a “tool 

box” is useful in describing elements of 

the IPM story. 

Measure twice, 

cut once…. 

This is the prime directive of any 

DIY’er. In IPM, field scouting, accurate 

pest identification, and threat assessment 

is essential before any decision is made 

to treat a site. UC Statewide IPM provides 

these guidelines for over 40 crops 

in California, which provides the basis 

for decision making. When a pest population 

exceeds the recognized threshold 

for damage and action is required to prevent 

economic loss, it is critical to have 

access to the right tool (http://ipm.ucanr. 

edu/PMG/crops-agriculture.html). 

Diversity of Tools 

The odds are that there are several 

tool boxes around your house, in the 

garage and in your truck. Some boxes 

may hold tools specific to some problem 

while others are more general in their 

application. However, when something 

needs to be repaired around the house, 

the right tool is essential. For example, if 

a light fixture needs repair, having only 

a pipe wrench in a tool box is not much 

use. 

In the same vein, IPM works best 

when a diversity of tools are available to 

respond to specific problems. In most 

cases, the problem being addressed 


presents imminent threat to the crop. 

When the situation requires an immediate 

response (or fix), it is important to 

have a wide selection of chemical tools 

with a diversity of active ingredients. 

Having access to active ingredients with 

multiple modes of action and selectivity, 

is important in keeping the tools “sharp”. 

Similar to your tool box, overuse of a 

tool results in it becoming dull. 

If you see all problems 

as nails….. 

Just having a diverse choice of tools is 

not enough. Seeing all problems as nails, 

your only tool becomes a hammer. In 

IPM, a hammer is a big tool, designed to 

take care of the problem immediately. As 

any handyman knows, it is important to 

avoid collateral damage to your thumb 

when using a big hammer. 

Big jobs need blueprints….. 

Besides small home maintenance 

jobs, tools are used for large construction 

jobs. For these, having complete 

blueprints is critical to manage the construction 

process. For IPM, it is important 

to take the long view of managing 

pests. Developing a plan for managing 

pests in the context of the agro-ecosystem 

is essential for sustainable agriculture. 

Creating an IPM plan provides a 

reflective opportunity to review current 

practices and access all the tools available 

in the IPM tool box. 

UC IPM has worked with United 

States Department of Agriculture 

(USDA)-Natural Resource Conservation 

Service (NRCS) to develop a planning 

process which incorporated IPM into the 

NRCS resource conversation farm planning 

process (http://ipm.ucanr.edu/PDF/ 

PMG/NRCS_Step-By-Step_Instructions. 

pdf). Using the UC IPM Guidelines, one 


The same is true for IPM. Many of 

our large hammers are broad spectrum 

insecticides with potential collateral 

damage to the ecosystem being managed. 

Such broad spectrum tools can 

destroy the balance in the field or orchard 

by removing natural enemies and 

result in resurgence of the primary and 

secondary pests, placing your field onto 

the pesticide thread mill. 

Using many little 

hammers…. 

One of the concepts IPM practitioners 

espouse is the use of “many small 

hammers”. By this we mean increasing 

the mortality of the pests through multiple 

approaches. For example, recent, 

innovative biorational insecticides may 

not provide the expected level of control 

of previously used chemical classes, but 

have less impact on the natural enemy 

complex which provides additional mortality 

sources. Not only do the natural 

enemies act as many small hammers, 

using selective, suppressive insecticides, 

adds additional smaller hammers to 

increase the overall population management. 

These non-chemical practices are essential 

but underutilized tools in the tool 

box. While chemical tools are critical 

for immediate intervention, the cultural, 

biological and crop production practices 

are essential for managing pests in the 

long term. 

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can review current practices, identify 

potential environmental issues, suggest 

alternative approaches (chemical, biological 

and cultural), and provide documentation 

of progress. 

In addition, UC IPM has developed 

a decision support tool (DST) for alfalfa, 

almond, citrus and cotton (http://www2. 

ipm.ucanr.edu/decisionsupport/). This 

tool provides an easy approach to the 

UC IPM Pest Management Guidelines 

(PMG), allowing for an easy comparison 

of chemical and non-chemical 

approaches across multiple arthropod 

pests. DST provides a convenient report 

including pest identification, population 

assessment, evaluation of the threat, and 

review of all management and control 

options. 

Within the report, links provide 

specific guidance from PMGs to review 

options with grower clients. Chemical 

options provide resistance management 

information, impact on 

beneficial predators, parasites, 

pollinators, and surface water 

quality concerns. The report 

provides an IPM annual plan 

and meets the requirement on 

written recommendation that 

PCAs have “considered alternatives 

and mitigation measures 

that would substantially lessen 

any significant adverse impact 

on the environment have been 

considered and, if feasible, 

adopted”. 

How do we get new 

tools? 

The IPM Tool Box depends 

on both private and public 

sectors to fund new and innovative 

tools and practices. The 

insecticide tools are developed 

with private investment requiring many 

years of research and registration process 

with hope of successful payoffs. As mentioned, 

these tools are the first to be used 

as intervention. 

The other tools in the tool box are 

developed with public sector funds or 

commodity based assessment fees. The 

latter tends to address immediate and 

intermediate issues such as invasive 

species or resurgence of endemic pests. 

These funds tend to be directed toward 

the “problem du jour” and seeking immediate 

results. 

Public sector funds have been directed 

toward research seeking solutions to 

intermediate and long term issues. These 

have supported independent projects 

which can be directed to problems not 

covered by other resources. As part of 

the original UC IPM Program “charter”, 

a competitive research program was conducted 

for over 20 years. This program 

provided the basis for many of the Pest 

Management Guidelines including sampling, 

threat assessments, management 

options, phenology models, cultural 

and biological practices, and pest/crop 

interactions. 

Unfortunately the research component 

of UC IPM was lost during the UC 

budget reductions in the early 2000’s. 

The loss of these public funds has impacted 

our ability to consider and pursue 

longer term questions. It has especially 

affected those crops which cannot support 

a research assessment program such 

as many row and field crops. 

The IPM Tool Box is filled with 

tools which can wear out and need 

replacement. While private investment 

is available for chemical tools, public 

investment is less available for cultural 

and biological control tools. Without 

public commitment to IPM, the tool box 

will continue to become less diverse and 

robust, creating a dependence on fewer 

alternatives and increasing our reliance 

on insecticide options. 





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BOTRYOSPHAERIA 

Botryosphaeria are a group of fungal 

pathogens that have been well-known 

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and significant production loss to the 

disease in the late 1990s. However, 

Bot pathogens have emerged as 

a growing challenge to walnut tree 

health and yields in California in the 

past three to four years. In walnuts, 

Bot can easily spread from tree to 

tree by wind or water, and spores 

germinate with a quarter-inch of rain 

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to water. 

The disease has a multi-season 

impact on orchards. Bot infects and 

damages the current year’s fruit, and 

also the fruit wood that will produce 

fruit the following year. 

“In some mature walnut orchards, 

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with additional declines the second 

year and potentially devastating 

impacts to the health of trees in 

the orchard,” said Chuck Gullord, 

a technical sales representative 

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Botryosphaeria spores germinate 

and enter the tree through existing 

wounds or scars, such as those 

from pruning, leaf and fruit drop or 

bud scars. Research conducted by 

the University of California in 2014 

found that untreated wounds can 

be susceptible to infection from 

Bot fungi for extended periods. For 

example, pruning wounds in medium 

to large branches can be infected 

for at least four months after the 

pruning cut is made. 

“Walnut trees with scale 

infestations are 

60 to 70 

percent more 

prone to Bot infection.” 

While walnut scale damage 

has historically not been 

considered a significant 

economic threat to walnut 

production, the lesions on 

trunks and old branches 

caused by scale are a key 

entry point for Bot infection. 

Walnut trees with scale 

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on 4/16, 5/15, 6/25, 7/25 and 10/30. Harvest on 9/29. Plots: 11 rows, 2 rows harvested per plot. 

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27

NITROGEN FERTILITY 

MANAGEMENT 

OF COOL SEASON 

VEGETABLES: 

A yearround 

perspective 

By Richard Smith | Vegetable Crops Farm Advisor, 

Monterey County, CA 

Effective nutrient management is 

critical to successful and economical 

production of cool-season vegetables 

on the Central Coast of California. The 

coastal valleys produce 90 percent of 

the lettuce for the US market during the 

summer production season. Since the 

1920’s when lettuce was first shipped 

by rail across the country, nitrogen (N) 

fertility practices were developed to be 

successful over a wide range of soil types 

and irrigation practices. The cost of N 


Lettuce. 

All photos courtesy of Richard Smith. 

fertilizer is a small percent of growing 

costs (5-6 percent) and, N fertilizer rates 

that guarantee successful crop production, 

may exceed crop uptake and 

not result in environmental efficiency. 

However, regulatory pressure from the 

Regional Water Quality Control Boards 

are compelling growers to implement 

fertilization practices that improve N use 

efficiency. Many growers have embraced 

this challenge and are making progress 

to bring the rates of applied N much 

closer to the levels of uptake by the crop. 

To do so, growers are embracing new 

knowledge regarding fate and availability 

of N during the growth cycle. 

Ammonium and nitrate are the 

forms of mineral N primarily taken 

up by plants. In warm soils during the 

summer, ammonium nitrifies rapidly to 

nitrate which is the main pool of residual 

soil N available for crop growth. However, 

the nitrate molecule has a negative 

charge, is not adsorbed by soil colloids, 

and is highly mobile with water passing 

through the soil. As a result, at the 

beginning of the crop cycle in years with 

normal to above normal winter rainfall, 

soils typically have low levels of residual 

soil nitrate (e.g. < 10 ppm NO 3 

-N) because 

of leaching. Knowing the levels of 

residual soil nitrate helps guide fertilizer 




29

Table 1 Typical macronutrient uptake and harvest removal of annual vegetable crops at 

normal yield levels. Continued from Page 29 

Crop Seasonal crop uptake (lb/acre) % nutrient 

removal 

N P K with harvest 

Broccoli 250-350 40-50 280-380 25-35 

Brussels Sprouts 350-500 40-60 300-500 30-50 

Cabbage 280-380 40-50 300-400 50-60 

Cantaloupe 150-200 15-25 170-250 50-65 

Carrot 150-220 25-40 200-300 60-70 

Cauliflower 250-300 40-45 250-300 25-35 

Celery 200-300 40-60 300-500 50-65 

Head or Romaine Lettuce 120-160 12-16 150-200 50-60 

Baby Lettuce 60-70 5-7 80-100 60-75 

Onion 150-180 25-35 200-260 65-75 

Pepper (Bell) 240-350 25-50 300-450 65-75 

Potato 170-250 30-40 250-300 65-75 

Processing Tomato 220-320 35-45 300-400 60-70 

Spinach 90-130 12-18 150-200 65-75 

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decisions because, if levels are 

low, fertilization is necessary, 

but if levels are high, fertilizer 

applications can be reduced or 

skipped. 

Table 1 shows typical levels 

of N taken up by several crops 

grown in Monterey County. 

The uptake of N can vary to 

some degree from these values 

depending on yield potential 

of the crop and residual N in 

the soil. During the crop cycle, 

N uptake by crops follows a 

typical sigmoidal curve. For instance, 

in direct seeded lettuce, 

small amounts of N (about 10 

lbs N/A) are taken up by the 

crop during the first 24–28 

days of the crop cycle. This 

amount of N can be supplied 

by a modest application of 

starter fertilizer or by N in an 

anticrustant. However, during 

the next 35-40 days to harvest, 

N uptake is 3-4 lbs N/A/day 

following a linear uptake pattern. This 

is the key part of the crop cycle that we 

evaluate levels of residual soil nitrate to 

make effective fertilizer decisions. 

Adjusting fertilizer N 

applications based on 

soil nitrate-N 

Soil nitrate levels are measured prior 

to post-thinning N applications in the 

top foot of soil for most cool-season 

vegetables. Samples can be analyzed for 

nitrate by a commercial lab. However, 

the nitrate quick test (http://ucanr.edu/ 

blogs/blogcore/postdetail.cfm?postnum=4406 

) is used to analyze soil on 

the same day to facilitate making fertilizer 

decisions based on the current levels 

in the soil. If residual soil nitrate levels 

are low (20 ppm NO3-N) indicate that 

the fertilizer application can be greatly 

reduced or skipped. Residual soil 

nitrate-N levels of 20 ppm NO 3 

-N in the 

top foot of soil is equivalent to 70 to 80 

lbs of N (depending on soil bulk density) 

and this quantity is sufficient to supply 


the crop for 10-14 days. Soil nitrate levels decline later in the 

crop cycle due to crop uptake and losses from leaching, and 

residual soil nitrate can be measured again prior to the next 

fertilization event to determine further fertilizer N needs. Residual 

soil nitrate levels of 20 ppm during the critical growth 

period following thinning indicates sufficient N is available 

for optimal crop growth. However, in the week prior to harvest 

soil nitrate levels can decline to below this level without 

jeopardizing crop yield. 

Nitrate in 

Irrigation Water 

Nitrate in irrigation water can also supply N for crop 

growth. The quantity of nitrate-N in irrigation water can be 

calculated from the following formula: 

ppm NO 3 

-N in irrigation water x 0.227 = lb N/acre inch of 

water 

Table 2 N in irrigation water and typical crop water usage 

ppm NO 3 

-N 

in irrigation 

lbs N/acre 

inch 

10 2.3 16 – 23 

20 4.5 32 – 45 

40 9.1 64 – 91 

60 13.6 95 – 136 

lbs N for a crop using 

7 – 10 acre inches water 

Nitrate in irrigation wells along the coast vary from less 

than 10 ppm NO 3 

-N to wells that have greater than 50 ppm 

NO 3 

-N. Calculating the quantity of N supplied by the irrigation 

water is made by multiplying the seasonal water uptake 

of the crop by the nitrate concentration of the water. Broccoli 

and cauliflower take up from 7-11 inches of water and lettuce 

5-9 inches of water. As can be seen in Table 2 waters supplying 

> 40 ppm NO 3 

-N can supply significant quantities of N 

for crop growth. In trials conducted in 2016-17, we observed 

that fertilization practices can be modified by a small amount 

(10 – 20 lbs N/A) with irrigation waters with < 20 ppm NO 3 

-N, 

however for wells with > 40 ppm NO 3 

-N, fertilization rates can 

be reduced more substantially (40 lbs to much more). 

Sources of Residual 

Soil Nitrate-N 

Levels of residual soil nitrate build up during production of 

the first crop which can result in substantial quantities of residual 

soil N at the beginning of the second crop. Residual soil 

nitrate-N comes from the following sources: mineralization of 

crop residues, unused fertilizer, NO 3 

-N in irrigation water and 

mineralization of soil organic matter. The quantity of N that 

remains in the field following harvest can be substantial (Table 

1, page 30) and can vary from 35 to >200 lbs N/A in spinach 

and broccoli, respectively. The concentration of N in crop residues 

varies from 2.5 to 5.0. Incubation studies of cool-season 

vegetable residues indicate more rapid mineralization of N with 

higher concentrations of N in the tissue; most mineralization 




31


occurs in the first 2-4 weeks after incorporation 

into moist soil, and the rate of 

mineralization of crop residues declines 

significantly after the first month. Tillage 

operations to prepare the soil for the 

second crop generally take 3-4 weeks 

during which time, crop residues from 

the first crop have sufficient time and 

generally sufficient soil moisture to complete 

decomposition, leaving a pool of 

available nitrate at the beginning of the 

second crop. 

For example, in a trial conducted 

in 2017 on second crop of head lettuce 

following rapini (generally containing 

140-150 lbs N/A in the crop residue @ 

5 percent N in the tissue), the levels of 

soil nitrate-N were 30 ppm at planting. 

This field also had 56 ppm NO 3 

-N in the 

water and provided an excellent opportunity 

to see how far we could reduce N 

applications under conditions of high 

ing). There were no differences in yield 

among the treatments. These data underscore 

the importance of residual soil 

nitrate, as well as nitrate in the irrigation 

water can have on crop nutrition. 

Nitrate Scavenging 

Scavenging of nitrate from the soil 

profile occurs when a crop takes up 

more N than has been applied as fertilizer. 

Several crops routinely take up more 

nitrogen than is applied. For instance, 

summer-grown broccoli is routinely fertilized 

with 160 to 200 lbs N/A, but takes 

up over 300 lbs N/A. It has roots that 

extend down to three feet or more in the 

soil which facilitates its ability to retrieve 

N from deeper in the soil profile to supply 

its N needs beyond what is supplied 

by fertilizer. In this sense, broccoli acts 

like an in-season cover crop by bringing 

nitrate that is at-risk of leaching, back to 

the surface where we get another chance 

at utilizing it. All crops have the potential 

of scavenging nitrate-N from the 

soil if we account for residual soil N and 

adjust fertilizer programs accordingly. 

The end of the production cycle, 

prior to the winter fallow, is the Achilles 

heel in our efforts to reduce nitrate 

leaching. Soil nitrate levels tend to rise 

during the fall and early winter because 

soil temperatures are still warm enough 

to allow for mineralization of crop 

residues and soil organic matter. Winter-grown 

cover crops such as cereals 

can capture this pool of residual soil 

nitrate and keep it in the crop biomass 

thereby reducing the leaching. Cereal 

cover crops have been shown to take up 

150 to 200 lbs N/A over the winter. This 

is an excellent practice for reducing the 

risk of nitrate leaching during the winter. 

Unfortunately, the economics of vegetable 

production in the Salinas Valley do 

not favor the use of cover crops and they 

are used on only 5-7 percent of the crop 

Table 3 2017 fertilizer & irrigation trial. Second crop of lettuce 

Treatment 

Applied water 

inches/A 

N in irrigation 

water lbs/A 

Fertilizer N 

applied lbs/ 

acre 

Total 

Cartons/ 

acre 

yield 

Percent 

24 count 

boxes 

Grower 7.9 100 63 1033 88.6 2.7 

BMP 9.1 116 7 1058 94.6 2.6 

Intermediate 9.1 116 32 1084 97.4 2.7 

Untrimmed 

head wt. 

lbs/head 

residual soil nitrate and irrigation waters 

with high nitrate content. Treatments 

included the grower standard practice, 

a best management practice (BMP) and 

an intermediate fertilizer treatment. The 

yield evaluations shown in Table 3 are 

of a commercial harvest (12 beds wide 

by the length of the field, 900 feet). The 

trial was conducted on a sandy loam soil 

that was sprinkler irrigated until thinning, 

at which time drip irrigation was 

installed and used to irrigate the crop 

until harvest. The irrigation water in the 

grower and BMP treatments applied 100 

and 116 lbs N/A in the irrigation water, 

respectively. Soil nitrate levels over the 

course of the season were high and no 

post thinning N applications were made 

to the BMP treatment (only 7 lbs N/A 

were added in the anticrustant at plant- 

Spinach is grown in high-density plantings on 80-inch wide beds with sprinkler irrigation. 


acreage. 

Other Techniques for 

Improving Nitrogen 

Use Efficiency 

Nitrogen technologies such as 

nitrification inhibitors and controlled 

release fertilizers have been evaluated for 

use on lettuce and spinach. In general, 

these technologies are most useful in 

situations with high leaching potential, 

such as sandy soils with high rates of 

irrigation. In the Salinas Valley crops 

grown on high density beds are the most 

difficult to effectively manage efficiently 

because the crops are shallow rooted and 

there is no opportunity to use drip irrigation. 

In studies on spinach grown on 

high density beds, nitrogen technologies 

such as controlled release fertilizers and 

nitrification inhibitors provided measureable 

but modest improvements in N 

use efficiency. The effectiveness of these 

materials will vary significantly from 

field to field based on soil type, temperatures 

and irrigation practices making 

benefits specific to a crop difficult to 

predict. However, over the long-term, 

these technologies can help to reduce 

N application rates while safeguarding 

yield. 

As mentioned above a weak link in 

reducing leaching of nitrate to ground 

water is the winter fallow period. We 

are evaluating the use of high carbon 

amendments, such as ground almond 

shells, to tie up (immobilize) nitrate in 

the soil. In studies conducted in Europe, 

this technique was shown to reduce 

15-25 percent percent of leaching of N 

from cauliflower residues. Initial trials of 

this practice are underway to determine 

benefits that this practice can provide in 

our cropping systems. 

In summary, a key practice to improve 

nitrogen use efficiency in intensively-managed 

cool season vegetable 

production systems include effectively 

utilizing residual soil nitrates and adjusting 

fertilizer application rates accordingly. 

Many growers are including more 

testing in their fertilizer programs and 

are making progress towards improving 

nitrogen use efficiency. 




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33

SAVE THE DATE 

Central Valley 

Alm nd Day 

Fresno Fairgrounds 

Commerce Building 

1121 S. Chance Ave, 

Fresno, CA 93702 

June 20, 2018 

Tulare County Fairgrounds 

215 Martin Luther King Jr., 

Tulare, CA 93274 

October 26, 2018 

Mid-Valley 

Nut Conference 

Modesto Jr. College Ag Pavilion 

2201 Blue Gum Ave, 

Modesto, CA 95358 

November 2, 2018 

Hosted by: 

New This Year! 

It’s finally happening, no more traveling. 

JCS Marketing is bringing the show to 

Kern County with the 1st Annual Kern 

County Ag Day! 

Mark your calendar for this must attend 

Ag Trade Show for all types of growers, 

processors and crop consultants. 

This free event will offer timely seminars 

with educational credits, equipment, 

exhibits, networking, prizes and more. 

Pre-Register today and support this local 

effort to bring a first class venue to your 

doorstep, so we can plan the best show 

for you! 

Kern County Fairgrounds 

1142 S P St, 

Bakersfield, CA 93307 

November 28, 2018 


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January/February 2018 www.progressivecrop.com 35

JOIN THE FIGHT 

AGAINST DISEASE. 

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57398 10/17

PCC January/February 2018

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