Citrograph May-June 2010 - Citrus Research Board

Citrograph 

May/June 2010 


CPDPC (AB 281) 

CHAIRMAN 

NICK HILL


MAY/JUNE 2010 • Volume 1 • Number 3 

Cover photo by CRB President Ted Batkin 

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An Official Publication of the Citrus Research Board 

IN THIS ISSUE 

4 On the Cover 

6 Editorial 

9 Industry Views 

10 Eyes under the soil 

12 G. Harold Powell, Part II: A religion of 

cooperation and the ascendency of the California 

Fruit Growers Exchange, 1905-1920 

16 The industry loses a legend with the 

passing of Dowlin Young 

18 Governor calls attention to ACP/HLB 

during World Ag Expo visit 

20 Scion/rootstock incompatibility as the 

cause of tree decline in Fukumoto navel 

in the San Joaquin Valley 

26 Citrus Quarantine, Sanitary, and 

Certification Programs in the USA 

Prevention of Introduction and 

Distribution of Citrus Diseases 

Part 1–quarantine and introduction programs 

Citrograph is published bimonthly by the Citrus Research Board, 323 W. Oak Street, 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. 

May/June 2010 Citrograph 3

ON THE COVER 

Citrus Pest and Disease Prevention 

Committee chairman Nick Hill. 

The cover of this issue features Nick Hill, Chairman of the Citrus Pest 

and Disease Prevention Committee. The CPDPC was formed through 

legislative action as Assembly Bill 281 and signed into law last year. The 

program became effective for the 2009-2010 fiscal year, and growers are now 

contributing through the assessment collection procedures conducted by the 

California Department of Food and Agriculture (CDFA). 

Nick received his B.A. degree in agricultural economics from Fresno State 

University. He served eight years as an agronomist and is currently manager of 

citrus operations for Greenleaf Farms. He joined the Board of California Citrus 

Mutual in 1998 and has served two full terms as the Chairman of the Board. Nick 

is married and lives in the rural Reedley/Dinuba area of the San Joaquin Valley. 

Assisting Nick in the administration of the CPDPC are Craig Armstrong, 

Vice Chairman, and Richard Bennett, Secretary/Treasurer. Armstrong is from 

the Coachella Valley with headquarters in Thermal, and Bennett has production 

operations in Tulare and Kern counties of the San Joaquin Valley. Also assisting 

Hill is Kevin Severns who chairs a committee for future structures of the program, 

Kevin Olsen who chairs a committee for communications, and James McFarlane 

who chairs a committee for membership. 

“The goal of the program is to provide support and services to CDFA and 

other organizations to protect the California citrus industry from threats of invasive 

pests and diseases. To this end, the Committee will be developing programs 

to detect and respond to these threats. The primary issue before the Committee 

is HLB/ACP. The Committee is committed to serving the industry in an effective 

manner and to assure that the grower contributions are used in the most 

efficient way possible,” stated Hill. The CPDPC consists of 14 grower/producer 

members and two citrus nursery representatives. The program also allows for 

the appointment of one public member. The Committee is seeking applicants 

for consideration for this position. 

The Committee currently meets monthly in various locations throughout the 

State. The next meeting is scheduled for July 27th in Riverside. The location of the 

meeting will be announced by CDFA prior to the meeting and will be available 

on the CDFA website. Growers and interested parties can receive information 

on the activities of the Committee by contacting CDFA offices in Sacramento. 

The CRB can assist in obtaining information about the CPDPC. Contact CRB 

by email at info@citrusresearch.org. l 

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At present, the Citrus Research Board has a crew of 15 trappers maintaining 

over 7,200 traps in the commercial citrus groves of 15 California counties. 

4 Citrograph May/June 2010

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 2009-2010 

District 1 – Northern California 

Member 

Alternate 

Allan Lombardi, Exeter Kevin Severns, 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 David Dir, 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 Ken Kelley, Hemet 

District 3 – California Desert 

Member 

William Stein, Oasis 

Public Member 

Member 

Seymour Van Gundy, Riverside 

Alternate 

John Turco, Indio 

Alternate 

Steve Garnsey, Fallbrook 

Citrus Research Board 

323 W Oak, Visalia, CA 93291 

PO Box 230, Visalia, CA 93279 

(559) 738-0246 

FAX (559) 738-0607 

E-Mail Info@citrusresearch.org 


EDITORIAL 

By JIM CRANNEY, President, California Citrus Quality Council 

Preventing the introduction of 

Huanglongbing to California 

A significant 

accomplishment 

was an agreement 

to implement an 

ACP suppression 

program along 

the California- 

Mexico border. 

By now you probably know the essence of California’s strategy to deal with Huanglongbing 

(HLB) -- “early detection and rapid response.” The Citrus Research 

Board (CRB), in partnership with the California Department of Food and Agriculture, 

is implementing a massive program to trap Asian citrus psyllids (ACP) in 

urban and commercial areas of the state and test psyllids for potential HLB infection. 

Another important facet of our strategy is to prevent the introduction of HLB from infected 

regions that are close to California. There are a number of possible avenues that HLB could 

find its way into California, but given the history of other phytosanitary threats to California, 

we know Mexico should be part of our overall effort to prevent the introduction of HLB in 

California. 

The California Citrus Quality Council (CCQC) was encouraged to lead California’s efforts 

to protect the Mexican and California industries from the introduction of HLB. Since 

2008, CCQC has been working with the Mexican citrus industry and regulatory authorities 

in the United States and Mexico to improve communications and coordination in our joint 

fight to prevent the introduction of HLB. 

In June 2008, the Asian citrus psyllid was detected in Tijuana, Mexico, and by September 

the psyllid had spread to San Diego. CDFA and their County partners implemented an 

aggressive suppression program including pesticide treatments of all host sites within 400 

meters of the detection site. It became clear that suppressing the psyllid in southern California 

would be extremely difficult, if not impossible, if psyllids continued to move into California 

from Mexico. 

CCQC led a delegation of growers and industry representatives to Mexico in October 2008 

to form a partnership with the Mexican industry and look for ways we could work together 

to protect our industries from HLB. While we were not sure 

how our visit would be received, we found the Mexican 

growers and Mexico’s regulatory authorities to be just as 

concerned about HLB as anyone in our industry. We agreed 

to continue to communicate and share information that 

would help stop the spread of HLB. A significant accomplishment 

in opening up our dialogue with Mexico was 

an agreement to implement an ACP suppression program 

along the California-Mexico border. 

This agreement paved the way for USDA’s Animal 

and Plant Health Inspection Service (APHIS) to partner 

with their counterparts at SENASICA (Mexico’s national 

plant quarantine service) to trap ACP in border towns in 

Mexico and treat detection sites with the same pesticides 

we are using in our suppression program in California. CDFA, APHIS 

and SENASICA now coordinate their ACP suppression activities so ACP is being controlled 

in California and across the border. 

APHIS is now in its third phase of treatments in Tijuana where psyllid populations have 

been reduced by approximately 70 percent since the treatments began nearly two years ago. 

APHIS provides approximately $1.2 million to conduct the border ACP suppression program 


which is carried out with a team of 

Mexican technicians employed by 

APHIS. APHIS shares their daily 

reports with the California industry, 

CDFA and APHIS officials in the 

United States to keep everyone apprised 

of new detections and progress 

of pesticide treatments. 

APHIS has recently expanded 

this activity to include trapping and 

testing of psyllids 100 miles south 

of Tijuana in the Baja Peninsula and 

south of the border in Sonora as far 

as Hermosillo. This activity is providing 

an early warning system so we 

will know if HLB is approaching. 

We have proposed an expansion of 

APHIS’ trapping and testing activities, 

but at the present time no funding 

is available. 

After HLB was discovered in 

Belize last spring, Mexican plant protection 

authorities started an intensive 

search for HLB in Mexican territories 

near the border with Belize. In July 

2009, HLB was found in the northern 

tip of the Yucatan Peninsula, and over 

the following months it was also discovered in Jalisco, 

Nayarit and Colima. 

Most recently, HLB was detected in backyard sites in 

the state of Sinaloa in the towns of Mazatlan and Teacapan. 

These states are clustered on the western coast of Mexico 

with the closest detection approximately 900 miles from 

the California border. Mexican authorities are removing the 

trees, and they continue to delimit the area to determine the 

full range of HLB infection. It has been reported that many 

of the detections in the Pacific states of Mexico have been 

discovered from visual symptoms, which means the disease 

has been present for two years or more. Mexican officials 

are concerned that HLB could have been spread by psyllids 

over this period of time. 

Mexican officials have also reported that Colima is an 

important lime and nursery production region. Over 200,000 

nursery plants have been destroyed in Colima due to HLB 

infection. The presence of HLB in a nursery production 

region means that the disease could have been distributed 

unknowingly for several months before HLB was discovered. 

This news is troubling when you consider the potential 

scope of the problem. 

Despite the overwhelming challenges these problems 

present, there are still opportunities we can explore to stop 

or slow the spread of HLB in Mexico. Over the next couple 

of months we plan to meet with growers in Sonora and 

Sinaloa to investigate the possibility of developing a growersponsored 

ACP trapping and testing program in Sonora and 

Sinaloa. We would also propose that growers develop an 

Huanglongbing locations in Mexico as of June 17, 2010. Map supplied by USDA 

Animal and Plant Health Inspection Service; data sourced from The National 

Service of Agro Alimentary Health, Safety, and Quality (SENASICA), Mexico’s plant 

protection and quarantine agency. 

areawide program to reduce ACP populations, to reduce the 

probability that the disease is spread rapidly by psyllids. We 

would also propose to discuss ways growers could partner 

with local and national authorities to monitor and control 

the movement of citrus nursery plants which can spread the 

disease. Finally, we plan to share information on how citrus 

industries in the United States have used grower funds to 

supplement county, state and national HLB activities. 

Trapping for ACP in border towns is, of course, a critical 

component of the US-Mexico collaboration to suppress the 

insect and prevent the introduction of HLB to California. 


A Mexican technician employed by 

APHIS uses a backpack sprayer to apply 

a foliar treatment for ACP. 

We will continue to look for other 

ways we can use cooperative activities 

to improve communication and work 

jointly to keep HLB out of northern 

Mexico and California. We’ll be sure 

to keep the industry posted as we 

make progress with this important 

priority.l 

The California-Mexico border ACP 

suppression program conducted 

as a collaborative effort of USDA 

and SENASICA includes soil drench 

applications as well as foliar. 

Treating Asian citrus psyllid detection 

sites in Tijuana, Mexico, is no easy task 

given the terrain and the sheer number 

of locations with citrus trees. 

The California Citrus Quality 

Council (CCQC) conducts the industry’s 

quality assurance program. 

The Council’s primary objective 

is to ensure that California citrus 

production meets domestic and 

international regulatory standards. 

CCQC works with government agencies, 

international standards-setting 

organizations, the University of 

California, the California citrus 

industry, and trading partners to 

help the California industry meet 

domestic and international phytosanitary, 

food safety, food additive, 

and pesticide residue regulations. 

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INDUSTRY VIEWS 

Citrograph asks: How will the increased threats 

of invasive pests and diseases impact your 

farming operations in the future 

Invasive pests and diseases are entering California agriculture at an increasingly rapid rate 

due primarily to the increase in people traffic around our globe. The research community 

can’t keep up with the pace of the onslaught to find solutions to these essentially human-caused 

problems. As a citrus/avocado/grape grower in Ventura and Monterey counties, the quarantines 

that follow these invasions present marketing problems at the very least, and directly affect the 

lives of all the participants up and down our agricultural food chain. All of our commodities 

have an export component that significantly adds to the value of the crop. These are in direct 

jeopardy of quarantine from countries that are trying to protect themselves just as we are. Additionally, 

there are the impacts of quarantine restrictions from field to packinghouse including 

harvest modifications, inspections, tarping and added administrative costs, if transport is even 

permissible. Our desert lemon growers are facing these dilemmas in the next several months as 

their fall crops become mature. The Asian citrus psyllid is being fought up and down the state as 

we speak. Currently, the disease that the psyllid can carry, Huanglongbing, has no cure and will 

kill the trees in fairly short order. Florida has the disease, and Texas, Arizona and California are 

trying to prevent it. Millions of dollars of federal, state and industry money are being spent to 

combat it. The grape industry has its own problems with the European grapevine moth that may 

have been introduced by infested smuggled budwood; it will cost millions. Our citrus industry has 

historically had excellent success with integrated pest management programs that have utilized 

targeted, relatively innocuous pesticides in conjunction with good cultural practices and beneficial 

insects to maintain good tree vigor and protect the industry from harmful pest populations 

as well as stronger pesticides. These programs may be jeopardized as the industry is forced into 

mandatory and more frequent pesticide treatments to have any market opportunity in the short 

term, and preserve the health of our orchards in the longer term. Infestations cannot be tolerated, 

as they jeopardize the entire industry. Organic growers may lose their certifications in the face of 

mandatory treatments. In Ventura County we farm adjacent to housing developments requiring 

detailed, careful spray applications by all operators. Untreated backyard trees in close proximity 

to commercial groves now pose a significant threat to the industry as they are likely sources of 

further infestation. Quarantines with additional spraying protocols will complicate all of our lives. 

What happened to simple — J. Link Leavens, General Manager/Partner, Leavens Ranches 

As a farm manager and citrus grower of approximately 400 acres in eastern Tulare County, 

the potential threats of new invasive pests and diseases are of great concern to our operations. 

Previous cultural practices have been established and implemented for pest control for 

many years. Traditional treatments for pests such as worms, mites, thrips and scales are common 

annual treatments. We know how to budget for these, and we know how to time the applications 

of the agricultural chemicals we currently use to obtain the maximum benefit. With the threat of 

new pests and the potential for diseases that they may carry such as HLB, there is still much that 

is unknown. Which current chemical applications will help control ACP How many additional 

treatments will be required What materials will we be able to use and what will be the additional 

costs How will the export markets react to the situation These are just some of the questions 

which we do not currently have answers to that cause us much stress. We can safely agree that 

new pests will increase our production costs. Let’s just hope that these increased costs will not 

exceed the income producing potential of any grove. At this point, pest exclusion seems to be the 

most effective control method. Unfortunately, we must be prepared to act quickly if an outbreak 

is detected in our area. After personally witnessing the devastation in Florida, the outlook is not 

encouraging. Our future is in jeopardy. Current citrus production will change or be eliminated. 

The thought of a grove being developed and managed for the next generations to also enjoy 

is also at risk. That is what I am worried about. — Dan Dreyer, Owner, Agricultural Services 


Eyes under the soil 

Carl T. Gwilliam 

Citrus growers know the importance 

of using irrigation water effectively 

and efficiently. But many growers 

are wondering how to make the most of every 

drop. Central Valley growers are finding soil 

moisture monitoring units just may be the 

answer. 

Irrigating tends to be a guessing game, but 

smart irrigation decisions come from knowing 

the status of your soil moisture at all times. 

Water and energy could be saved by knowing 

the exact amount of time it takes for water to 

reach the root zone. Water could be applied 

directly to the roots, and waste of our precious 

resource would be kept to a minimum. 

Soil moisture monitoring units are used 

for this purpose. They give you “eyes under 

the soil” allowing you to see the depth and 

amount of irrigation water in your soil. This 

knowledge can be used not only to improve 

irrigation efficiency, but also to prevent plant 

CropSense ® in the field. The system can 

be installed in all variety of plants – trees, 

vines, and row crops. 

stress and disease that comes from under- or 

over-watered roots. It also aids in fertilizer 

placement, by guiding growers in applying 

water run fertilizers directly into the root zone, 

reducing leaching and waste. 

Many of these systems use capacitance 

sensors at multiple depths (4”, 8”, 12”, 36”, 

48” and 60”) to give a more accurate reading 

of your soil water content and location. One of 

the most time-tested soil moisture monitoring 

systems is John Deere Water’s CropSense ® . 

Growers like these units because they communicate 

via satellite, so all the data is automatically 

transmitted to a password protected 

website and never has to be downloaded 

from the field. Satellite transmission works 

everywhere with no problem areas within the 

continental U.S. The data is recorded 24-7, 

and is transmitted every two hours, to a userfriendly, 

web-based account where growers 

and irrigation managers can access real-time 

Line Graph—Shows water and water usage at all depths. 

Flat lines indicate no water 

is reaching 36”. Since roots 

activity level slows significantly 

at 20” (shown by the 

almost flat line) little to no 

water is needed at these levels 

and no water is being wasted. 

Stair stepping indicates roots 

taking up water. This graph 

shows roots pulling water at 

4”, 8”, and 12”. 

Irrigation Started 

Irrigation Stopped 


information anywhere internet service is available. All data is password 

protected, and access is controlled by the grower. Because 

CropSense ® is owned by John Deere Water, growers know that 

the best technology and support will be available to them for the 

long-term. 

The information transmitted by the CropSense ® unit is retained 

so that growers can compare year to year. This gives them a convenient 

place to record and analyze previous irrigation practices 

and water usage. With the current water situation in California, the 

Sum Graph—Shows average soil moisture at all depths. 

Flat line indicates water 

has reached saturation. 

Any additional water 

added is wasted. 

Irrigation Stopped. 

Approximately 3 hours 

of water was wasted. 

possibility of water usage reporting to the government may be just 

around the corner. The data from soil moisture monitoring units 

allow growers to show that not only are they using their water to 

maximum efficiency, but also provides a record of the exact amount 

of water applied through the season for optimum production. This 

information can be invaluable in justifying annual water needs. 

Installing soil moisture monitoring units is a simple process, and 

they are effective in all types of crops, soils and irrigation systems. 

With each unit they install, a CropSense ® agronomist works with the 

grower to learn how to navigate 

the website, read the soil moisture 

charts, and improve their 

irrigation efficiency. Ongoing 

assistance is always available, 

but many growers have found 

that the data is extremely easy 

to understand when compared 

to the data of other soil moisture 

monitoring systems. 

Growers are optimistic 

about soil moisture monitoring 

units being a solution to managing 

their limited water resources, 

and costly fertilizer inputs. For 

more information on these units 

and how they work, visit www. 

IrrigationMatters.com. 

CROPSENSE ® is a registered 

trademark of John Deere 

Water. l 

Irrigation Started—Soils have become dry and need to be refilled. 

Line Graph—Shows water and water usage at all depths. 

Carl Gwilliam is a certified agronomist 

and the proprietor of Tulare 

Ag Products, Irrigation Matters, 

and the other TAP family of 

oompanies. 

Stair stepping indicates water 

is being taken up by the roots 

at all depths, except the 36” 

level. Grower has achieved 

efficient irrigation, and no 

water is leaching past the 

root zone. 

Irrigation started; water reaching all 

depths except the 36”. 


Citrus Roots 

Preserving Citrus Heritage Foundation 

The directors of this Foundation 

are elated and honored in having 

this opportunity to “showcase” 

our work through the Citrograph 

magazine. Our “Mission” is to elevate 

the awareness of California 

citrus heritage through publications, 

education, and artistic work. We 

are pleased with the response of the 

three current university displays: the 

University Library-Special Collections 

at Cal Poly Pomona, Pomerantz 

Library at Western University, 

and our largest display in the John 

M. Pfau Library at CSU San Bernardino. 

We are especially happy to 

report that the Foundation’s latest 

book has just arrived, titled Citrus 

Powered the Economy of Orange 

County for Over a Half Century Induced 

by “A Romance”. Please visit 

our website… www.citrusroots.com. 

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. 

A religion of cooperation 

and the ascendency of the 

California Fruit Growers 

Exchange, 1905-1920 

By 1915, and with the torque of a 

steel spring, the California Fruit 

Growers Exchange (CFGE, now 

Sunkist Growers, Inc.) deftly catapulted 

southern California onto the national 

stage. The CFGE had clearly emerged 

as a powerful engine of modernization, 

pulling California and the American 

countryside into the 20th century. A citrus 

marketing cooperative organized as 

a corporation, the Exchange leadership 

never hesitated to flex its muscle. As a 

marker of its clout, in 1921 CFGE sold 

$121,000,000 of oranges and lemons to 

the wholesale trade. It did so by marketing 

the fruit of 15,000 tough-minded 

California citrus growers, all members of 

the Exchange. Its premium trademark, 

Sunkist, had become a household word. 

For countless millions in the East, especially 

women, Sunkist was citrus, and 

citrus grew in California. 

In 1922, the Exc 

h a n g e h a n d l e d 

more than 70 percent 

of the entire California 

citrus production, 

at low marketing 

costs, by means 

of a large corps of 

salaried sales agents 

throughout the United 

States, Canada, 

and overseas ports 

of call. A vertically 

integrated enterprise, 

G. Harold Powell, Part II: 

H. Vincent Moses 

Pachappa Orange Growers 

Association, Riverside, 

California, origin of the CFGE, 

c1891. (Photo courtesy of Riverside 

Metropolitan Museum.) 

the CFGE owned its own Fruit Growers 

Supply Company, including prime 

timberland and sawmills in northern 

California. The supply company operated 

under the CFGE board of directors, 

providing raw materials at low cost to 

Exchange growers and packers. In this 

manner, CFGE exploited the economies 

of scale and scope in production and 

distribution. Through standardization, 

the elimination of decay, cooperative 

purchasing of supplies, the development 

of citrus by-products, and a systematic 

effort to stimulate demand through advertising, 

the Exchange promoted the 

growers’ interests in all aspects of its 

activities. 

From 1912 through 1922, G. Harold 

Powell sat at the helm of this gigantic 

vertically integrated enterprise. He 

fondly called the mammoth Exchange 

his Flying Wedge of Cooperation. In part 

I of our series, the 

charismatic Harold 

Powell had arrived in 

southern California 

as a rising star with 

the Bureau of Plant 

Industry of the Department 

of Agriculture. 

Now he served 

a s C F G E ’s f i r s t 

non-grower General 

Manager, taking his 

position in 1912. Supremely 

confident, 


and in command of an encyclopedic 

knowledge of citriculture and all phases 

of production and distribution, Powell 

especially appreciated “manly” commentary 

on his organization. He wrote 

that the CFGE can “do anything a bank, 

a railroad, or any other corporation can 

do. Nerve isn’t lacking in the Exchange 

fibre.” It was not lacking in his either. 

In an era when most farmers were 

still planting by the Moon, Powell reveled 

in the knowledge that the CFGE 

constituted a revolutionary business 

organization in agriculture, and he was 

its undisputed spokesman. Because of 

its organization, the Exchange surged 

ahead in an economic sector traditionally 

dominated by the rugged individualism 

of small proprietary farmers. By 

all reckoning, CFGE stood as what 

Pulitzer Prize-winning economic historian 

Alfred D. Chandler, Jr. has called a 

modern business enterprise; a vertically 

integrated managerial corporation, with 

region and industry-shaping clout. 

Powell fostered and molded the development 

of a modern corporate infrastructure 

for the Exchange, taking it into 

full-fledged status as a modern industrial 

enterprise. That work included, among 

other innovations, refinement of production 

standards through implementation 

of careful handling methods in grove 

and packinghouse, totally new designs 

for packing machinery and grove implements, 

scientific studies of various ways 

to improve the commercial uniformity 

and keeping quality of fruit, ways to 

increase the yield per acre, the ongoing 

preservation and enhancement of the 

mass distribution system, creation of 

new products and by-products, penetration 

of new markets, and professionalization 

of the management at all levels. 

He further led the Exchange to gross 

returns exceeding $100,000,000, built 

up the idea of cooperation to the level 

of a religion among citrus growers, and 

had made the Exchange a much envied 

and emulated model for other agricultural 

producers seeking to organize their 

operations through modern corporate 

methods. He managed this while keeping 

the Exchange clear of the Sherman 

Antitrust Act, not a small feat. 

Powell himself described the rise of 

the enterprise in a 1915 article for the 

original California Citrograph. He told 

readers that the growers had begun to 

cooperate to solve their mutual marketing 

problems as early as 1885. They 

direct or through an army of traveling 

salesmen. Exchange salesmen disposed 

of the remaining 30 percent of the fruit 

at public auction in New York, Chicago, 

and other key cities, to either wholesale 

or retail dealers. 

Powell’s 1915 Citrograph article 

placed the Exchange on par with the 

commercially sophisticated rough and 

tumble meat processor trusts, Swift and 

Armour. Employing state-of-the-art 

telegraphic communications technology, 

the central exchange of the newly structured 

CFGE managed to keep growers 

in constant contact with market trade 

conditions. CFGE agents in the United 

States, Canada, and other locations 

wired current information to the central 

agency in Los Angeles on a daily basis. 

By these cables, growers were apprised 

of amounts and condition of 

Exchange fruit in transit to each market, 

complete car-lot sales information, 

up-to-date weather reports, stocks of 

competing deciduous fruit entering the 

market against citrus fruits, and all other 

issues required to carry on intelligent 

daily transactions with the trade sevformed 

local associations, built packinghouses, 

hired professional managers 

from within the industry to coordinate 

the pooling of individual growers’ fruit, 

standardized grades, and branded and 

packaged fruit for market. Successful 

organization of these efforts at the local 

level led regional growers in 1893 

to incorporate under California law as 

the Southern California Fruit Exchange 

(SCFE). SCFE located its headquarters 

in Riverside. 

Then in 1905, the same growers 

reincorporated their producer-owned 

cooperative as the California Fruit 

Growers Exchange, assuming a fullscale 

hierarchical corporate structure. 

Through the new Exchange, the growers 

established sales offices staffed by 

trained sales agents at key distributions 

points among the country’s largest cities. 

Major cities in Canada also received 

Exchange offices and agents. Along with 

Exchange representatives in London, 

England, they sold about two-thirds 

of California’s massive citrus crop to 

2,500 fruit jobbers, who in turn sold it 

to 300,000 or more retail dealers either 

G. Harold Powell at the apex of his 

influence, c1917. This photo was 

taken as an official portrait during 

Powell’s tenure as Director of the 

Perishable Foods Division, War Food 

Administration, WW I. At Herbert 

Hoover’s request, the CFGE granted 

Powell a leave to serve with Hoover 

in Washington. Hoover credited 

Powell with winning the war at home 

through his “great generalship,” by 

implementing a nationwide system 

for coordinating the allocation and 

shipment of the country’s perishable 

food supply while diverting necessary 

shipments for military purposes. He 

hit the ground running by drawing 

upon proven CFGE production, 

distribution and communications 

methods, and his vast national 

network of contacts in the food 

trades. (Photo from Powell Family Papers, 

Powell Research Library, UCLA.) 

“How can a man hope to compete with you, 

when every night all over the California citrus 

belt every little boy and girl kneels at mother’s 

knee and prays, ‘God bless papa and mamma 

and the Fruit Growers Exchange’” 

Eastern Commission Agent to G. Harold Powell, General Manager, 

California Fruit Growers Exchange (1920) 


By: Rahno Mabel MacCurdy, V.A. Lockabey and others... 

compiled and edited by R.H. Barker 

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 

eral thousand miles away 

from the point of shipment. 

Moreover, the Exchange 

market news service 

made the latest information 

available to all Exchange 

shippers daily. To ensure 

thorough dissemination of 

complete information to 

growers themselves, the 

Exchange’s morning bulletin 

included every telegram 

that had passed between 

sales agents and fruit shippers 

concerning all aspects 

of the ongoing enterprise. 

It further contained special 

reports from private sale 

and auction markets. Weekly 

and monthly summaries 

of various components of 

the enterprise rounded out 

the effort to keep growers 

informed. 

This system, like that 

of the meat packer trusts, 

provided the significantly 

higher level of administrative 

coordination required 

to ensure the continuous marketing of 

a perishable product several thousand 

miles from the point of production. The 

creation and development of the growers’ 

logistically complex and dynamic 

marketing system placed the Exchange 

in the forefront of the citrus and other 

fruit industries. Similar actions had 

moved Armour and Swift, distributors 

of another kind of perishable product, to 

the lead positions among meat processors 

in the 1880s. 

Powell knew in his gut that Cal- 

Citrus Roots Series... 


National Orange Company, a closed corporation of the 

Ethan Allen Chase family, incorporated in 1901 with a 

capital worth of $801,000. Chase proved to be one of 

Powell’s staunchest supporters and a great advocate of 

the CFGE’s efforts to build a modern industrial base for 

citrus production and distribution. (Photo courtesy of Riverside 

Metropolitan Museum.) 

ifornia orange growers embodied 

Theodore Roosevelt’s modernizing 

aspirations for America. They were 

on a modernizing mission through 

cooperation. Unlike American small 

farmers generally, citrus growers embraced 

scientific management, electrical 

power, new-fangled gas-powered farm 

machinery, telephones, traction systems, 

and automobiles. Above all, they were 

organized and politically powerful. The 

Exchange provided a potent argument 

for the power of cooperative marketing 

NEWEST RELEASE!! 

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 

through grower-owned 

organizations. By wedding 

the citrus enterprise with 

Country Life ideology, 

and technological modernity, 

Powell had given the 

leading orange growers of 

southern California a potent 

systematic rationale 

for the corporate reconstruction 

of their industry. 

He gave them, in short, a 

religion of cooperation. 

While the Exchange 

began, in 1893, as an entrepreneurial 

corporation, 

by 1921 it was a modern 

business enterprise. The 

CFGE employed at least 

20 department heads, handling 

all phases of the 

operation, including transportation, 

legal issues, 

sales, advertising, field 

promotion, and research 

and development, among 

other matters. A hierarchy 

of salaried executives 

managed the organization. 

These managers carried out the policy 

set by a self-perpetuating board of directors, 

repeatedly re-elected by the boards 

of the district exchanges belonging to 

the CFGE. 

The Exchange applied industrial 

labor practices. It employed workers 

from the periphery of capitalism and 

housed them in Exchange or growerowned 

facilities in a manner similar to 

Eastern manufacturing. CFGE applied 

principles of scientific management in its 

member packinghouses, running them 

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Citrus Roots...Our Legacy - Volume I 

Selling the Gold - History of Sunkist® 

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Citrus Roots...Our Legacy - Volume II 

Citriculture to Citrus Culture 

Citrus Roots...Our Legacy - Volume III 

Our Legacy...Baldy View Entrepreneurs 

- 25 men & women who left a legacy 

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ENTREPRENEURS 

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(Fed. Tax ID # 43-2102497) 

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

with the efficiency of Henry Ford’s automobile 

plants. Designed by Exchange 

Field Department engineers, in alliance 

with packinghouse machinery manufacturers 

Stebler and Parker of Riverside, 

these houses were fully functioning 

assembly lines, operating in plants of 

optimal unit size for quality production. 

Between 1893 and 1920 then, leading 

large-scale orange growers and their 

General Manager diffused the ethos 

of the corporate culture throughout 

the region. Under Powell’s tenure, socalled 

“ten-acre” growers, who made up 

more than 80 percent of the Exchange 

membership, were willing to join the 

CFGE precisely because it stabilized 

the production and distribution of 

their fruit. In the process of winning 

over the small growers, Powell’s CFGE 

transformed the southern California 

landscape, reshaped the organization 

of work, and strategically cultivated a 

mythology of California as an American 

Mediterranean. Under their aegis, 

California took on the air of a “promised 

land,” a fertile place of new beginnings 

and possibilities. “Oranges for Health- 

California for Wealth,” the Southern 

La Atalaya, William Porter’s 26 

room “winter” estate, Arlington 

Heights, Riverside, c1916. Porter, 

President of the Southern Sierras 

Power Company, owned 600 acres 

of Washington navel oranges, and 

exemplified the business elite that 

brought a corporate mindset to 

the business of citrus. (Photo courtesy 

of Riverside Metropolitan Museum.) 

Pacific proclaimed, and Americans 

bought the concept. 

Powell’s leadership capped this 

transformation. His work enabled grow- 

ers, and later other farmers, to retain a 

form of Jeffersonian agrarianism, while 

simultaneously appropriating the power 

of corporate business combination. Powell’s 

form of agrarian godliness justified 

mutual cooperation in the service to 

farming as an individual way of life. His 

growers, he maintained, were simply 

small farmers banded together for mutual 

benefit. They were not intent upon 

market domination, or arbitrary pricefixing 

power. Powell’s growers simply 

had the religion of cooperation and 

knew its benefits. By calling the CFGE 

an “industrial democracy,” and by insisting 

that individual producers retain their 

rights as individual property owners, 

the Exchange effectively ensured its 

place among these small-scale growers. 

Within ten years, CFGE had enabled 

the thousands of California’s so-called 

“ten-acre” growers, in tandem with the 

large-scale growers to succeed beyond 

their wildest dreams. 

Dr. Vince Moses, Owner, VinCate 

& Associates Museum and Preservation 

Consultants, is an Advisory Board 

Member of Citrus Roots, Preserving 

Citrus Heritage Foundation. l 


Dowlin L. Young, co-founder 

of Young’s Nursery, one of 

California’s largest wholesale 

nurseries, died June 15, 2010 at his 

home in Thermal. He was 79 years 

old. 

Born in Orange County, 

California, Dowlin moved to the 

Coachella Valley in 1954 to start 

Young’s Nursery and remained 

active in its daily operations until 

his death. 

The program for Young’s 

memorial service noted that he 

was a supporter of the Coachella 

Valley Agricultural Research 

Station and the University of 

California Citrus Experiment 

Station, “contributing to new 

developments and practices in 

citrus cultivation in California. 

Dowlin was a pioneer in the 

California citrus nursery industry 

and at one time was the most 

prolific grower in the state, 

producing 600,000 trees annually. 

He was also responsible for the 

propagation and development 

of the ‘Daisy’ mandarin, a cross 

between the ‘Fortune’ and 

‘Fremont’ mandarins, named for 

his business partner and wife of 

nearly 56 years, Daisy.” 

The beautifully written tribute 

for the service emphasized that 

“Dowlin’s wit was matched 

only by his generosity, humility, 

and kindness. He remained 

active in the lives of his 

children, grandchildren, greatgrandchildren, 

extended family 

and friends until his death, 

and consistently served as a 

source of comfort, support and 

lightheartedness for many… This 

trademark self-effacing humor 

paired with Dowlin’s unrelenting 

work ethic allowed for close 

and life-long relationships with 

relatives, friends, employees, and 

colleagues alike.” 

In Memoriam 

Dowlin Louis Young 

October 29, 1930 – June 15, 2010 

The industry loses a legend 

with the passing of 

Dowlin Young 

As news of his passing 

spread, the 

Citrograph desk 

at the Citrus Research 

Board received many 

phone calls and emails full 

of wonderful reminiscences 

about this man, who 

was truly a legend and an 

icon in the industry. 

n Dr. Tracy Kahn, UC 

Riverside, wrote this note 

to Dowlin’s grandson Sam 

Glick, who shared it with 

Citrograph: “I am so sad to hear about 

your grandfather’s passing. He was such 

a wonderful man and successful citrus 

nurseryman. His efforts clearly changed 

the citrus nursery industry for the positive. 

He was also great fun to be around. 

I remember that he was present on the 

very first tour I gave for the industry at 

the Coachella Agricultural Research 

Station. I was nervous, and I cut my 

finger while cutting fruit for everyone. 

He snagged the knife from my hand and 

said ”you talk, I’ll cut fruit”. Dowlin was 

instrumental in making my mandarin 

variety trial and lemon trial at CVARS 

possible. We truly appreciate his support 

of our research… You should know that 

your grandfather was definitely held in 

very high regard by researchers and the 

nursery industry, also loved, and will be 

truly missed.” 

n Citrograph editor Margie Davidian 

spoke with CRB Board Member Kevin 

Olsen of Paramount Citrus who had 

many kind words to say about Young, 

including that he “had a never-tiring 

work ethic which was unparalleled.” 

Olsen said one of several 

great memories he 

has of Dowlin is that 

he had a large order of 

buds with Dowlin. Olsen 

called Dowlin to check 

on it at about 4 p.m. one 

June afternoon. Dowlin 

explained that he was 

doing the cutting himself 

because he didn’t want to 

leave it to someone else. 

Olsen recounted, “I said 

‘isn’t it awfully hot to be 

doing that right now’, 

and Dowlin’s retort was ‘Hey, don’t 

worry about it, OK The temperature’s 

already dropping, and it’s down to 

110’ ”. Olsen added that “in all business 

transactions, Dowlin always wanted a 

win-win solution”. 

n This came in from Dr. Peggy Mauk, 

UC Cooperative Extension: “Dowlin 

Young was an intelligent, witty, dynamic 

grower, colleague and friend. He made 

an impact and impression on everyone. 

Dowlin was a strong supporter of the 

University and wanted what was best for 

industry and the grower, putting himself 

second. One time, when Tracy Kahn and 

I were planning a mandarin variety trial 

for the lower desert, Dowlin came out 

to the research plots unannounced. We 

started talking about the best rootstocks 

for mandarins. I told him I thought 

a particular rootstock would do well 

because the fruit ripened earlier and 

the fruit had a better finish; both attributes 

would be to the advantage of the 

grower. He smiled at me and said, get in 

the truck. He proceeded to take me to 

an established experimental mandarin/ 


ootstock trial. He started cutting fruit 

and said “try this.” Followed by “what do 

you think of that” After we compared 

one scion on numerous rootstocks and 

consumed several fruit, he said, ‘so you 

liked this one best--that’s because of the 

rootstock; flavor always sells’. His lessons 

on life extended beyond his knowledge 

of citrus and agriculture; he even 

gave wonderful parenting tips. Dowlin 

was a brilliant, loving and compassionate 

man. The industry has lost a giant 

and a friend. I will miss you Dowlin.” 

n Jackie Maxwell writes that, “Shortly 

after I purchased Willits & Newcomb 

Citrus Nursery, I had the pleasure of 

meeting with Dowlin Young at his 

nursery in Thermal, CA. My 

first memory was stepping 

into the office and seeing the 

picture of George Washington 

with a crew cut (eerie resemblance 

to Dowlin). Under 

that picture was a sign that 

read “The Golden Rule – He 

who makes the gold, makes 

the rules.” I was in awe of the 

king of citrus nurseries and 

continue to be star-struck to 

this day. Over the last 32 years, 

Dowlin was my mentor, my competitor, 

the best loan officer I ever had and a 

true friend. I never asked a question that 

was not answered with complete candor. 

His warmth, kindness, knowledge and 

wit will remain a fond memory always.” 

He was a 

master of 

innovation 

and a 

humble 

host. 

n Finally, Citrograph received this 

tribute to Young from Roger Smith of 

TreeSource Citrus Nursery: “I consider 

Dowlin Young to be one of my mentors 

in the citrus nursery business. There will 

never again be anyone like him in our 

industry! He grew up in and around the 

nursery business his whole life. He was 

tying buds behind his dad at 8 years 

old and celebrated his honeymoon by 

making his wife work on a topworking 

job (I suspect he never heard the 

last of that decision.) He named the 

‘Daisy’ mandarin after his wife, Daisy, 

which showed his unique affection for 

his life mate. 

“Dowlin always ended a conversation 

with a joke, and all who knew him 

respected him for his down-to-earth 

approach to the citrus nursery business. 

He was a very practical man and allowed 

other nurseries to sell his trees for him, 

thereby fostering a standard of cooperation 

between citrus nurseries in California 

that lasts to this day. He was a man 

of opinions, but he would rarely express 

them publicly as he did not see himself 

as a man of industry influence. In his 

mind, he didn’t have time for meetings, 

so he let us youngsters do the meetings 

and would call us privately to teach us 

his perspective and offer his wise counsel, 

which was normally succinct, to the 

point, and with a touch of humor. 

“For decades, Dowlin was the primary 

supplier of budwood to nurseries 

throughout the state. He cut well over 

2 million buds a year and cut every bud 

himself to be sure there were no mistakes. 

He even had his truck stolen at 

least twice because he used to keep the 

keys in the ignition and listen 

to the radio while cutting 

buds deep in a nursery row. 

California citrus nurseries 

have to work harder making 

buds because Dowlin won’t 

be there to bail us out if we 

run short. 

“He was the consummate 

desert nurseryman and 

developed a system for his 

workers to dig trees at night 

in order to avoid the intense 

desert heat that started up in late 

spring. He was a master of innovation 

and a humble host. If you visited him, 

he would always have you jump in his 

truck for a tour of his three nursery sites, 

but you would have to observe his innovations 

for yourself because he would 

rarely point anything out. Lucky for me, 

I asked him many questions and learned 

a lot from his humble and often ribald 

answers. He would drive you through 

his vast nursery growing grounds that 

was home to well over a million trees at 

any one time, ticking off what varieties 

were and never pausing to look at a 

sign. I asked him how he did that and 

he looked me in the eye and said, ‘I’ve 

been doing this for a lot of years, and 

when you cut all the buds yourself you 

know where everything is.’ 

“Dowlin can never be replaced, but 

his legacy in our industry is as permanently 

rooted as the trees he supplied. 

Around the citrus industry you won’t 

find his signature, just his fingerprints. 

I am proud to have known a man of 

selfless character and humility, and all 

that I learned from him will always be 

a part of every nursery tree I produce. I 

will miss him…” l 

Reach 

Commercial 

California & 

Arizona Citrus 

Growers 

Whether you're selling tractors or 

other farm equipment,pickup 

trucks, irrigation equipment, fertilizer 

or pesticides...consider the value of 

your ad dollar in the pages of Citrograph. 

Each issue reaches every commercial 

citrus grower in the states of California 

and Arizona, plus associated business 

members affiliated with the citrus 

industry...the people in charge of 

purchasing. Your advertising message 

is directed to farm leaders who use vast 

amounts of goods and services. 

Circulation reaches over 5,000 key 

decision makers among California and 

Arizona fresh citrus growers, landowners 

and industry-involved companies. 

In the near future, Citrograph will reach 

the entire United States. Don’t miss 

the next issue! 

Contact us today to be 

included in future issues 

of Citrograph 

Sandy Creighton, Sales Manager 

Phone: 559-433-9343 

E-mail: screighton@farmprogress.com 


Governor Schwarzenegger at center with Secretary Kawamura at left and 

orange jacket, at right. Flanking the Governor are Assemblywoman Jean 

Connie Conway (34th district), right. Visible in the background (at left) is 

the team staffing the exhibit, and CRB President Ted Batkin (in tan jacket 

Governor calls attention to ACP/HLB 

during World Ag Expo visit 

California Governor Arnold Schwarzenegger 

and Agriculture Secretary A. G. Kawamura 

put the citrus industry in the spotlight at the 

2010 World Ag Expo in Tulare by choosing the 

Citrus Research Board exhibit as their only 

“meet-the-media” stop while touring the grounds. 

Schwarzenegger held an informal press conference 

at the booth, putting major emphasis on 

the Asian citrus psyllid and the threat of HLB 

disease. As in previous years, CRB’s exhibit – 

(which is in a prime location in heavily-trafficked 

Pavilion A) – showcased an attention-getting array 

of citrus varieties to pull people in, while the other 

half of the booth this year featured the industry’s 

action plan against ACP/HLB and the work of the 

CRB Operations Department. The World Ag Expo, 

which is better known in the ag community as simply 

“the farm show,” is the world’s largest annual 

agricultural exposition with 1,600 exhibitors over 

2.5 million square feet of exhibit space. The Expo 

is always scheduled for the second week in February. 

Photos provided by International Agri-Center. 


1992 Expo Chairman Mark Watte in the official 

Fuller (32nd district), left, and Assemblywoman 

Dr. Tracy Kahn, UC Riverside, a key member of 

and hat). 

The Governor shows an interest in several other aspects of the CRB program, including new 

variety development. CRB President Ted Batkin talks with him about the ‘Tango’ mandarin. 

Schwarzenegger examines a yellow sticky panel trap containing Asian citrus psyllid specimens hand-planted alongside other insects. 


CRB Funded Research Reports 2009 

Research Project Final Report 

Scion/rootstock incompatibility as the cause of tree decline 

in Fukumoto navel in the San Joaquin Valley 

Craig E. Kallsen and Neil V. O’Connell 

Buyers like the fruit of Fukumoto 

navel, with some 

asking for it by name. The 

fruit is early, attractive in shape 

and color, and has good size. 

However, since its introduction 

in the late 1980s, many Fukumoto 

navel trees in the San Joaquin 

Valley have grown poorly, 

declined or died. Fukumoto has 

exhibited what appears to be a 

disease, physiological disorder, 

or greater attraction for ants and 

associated damage, called foamy 

bark rot, which occurs during hot 

weather when the trees are two or 

three years old. As the tree ages, 

whether or not it exhibited earlier 

symptoms of foamy bark rot, 

further problems that may develop 

include: stunted growth of 

the tree with excessive suckering 

at or above the graft union that 

may produce a tree with multiple 

weak scaffolds coming directly 

from the graft union; delayed 

fruit maturity; over-growth of the 

scion and rootstock; and, in some 

instances, decline and death of the 

tree. The orchards exhibiting the 

poorest growth are on trifoliate rootstocks and its hybrids. 

Declining trees are most obvious and common as the trees 

reach maturity. Surveys of growers’ fields in 2003 and 2004 

suggested that decline was not associated with trees coming 

from a particular nursery or budline source. Although not 

directly part of this project, affected Fukumoto trees have 

been tested for various citrus diseases, including citrus tatter 

leaf capillovirus, leaf blotch and other viruses, viroids 

and citrus stubborn spiroplasma, without finding a common 

organism. Early field observations suggested that irrigation, 

freeze events and soil pH might be negatively influencing the 

health of Fukumoto trees. 

The objective of this study was to compare growth characteristics 

of Fukumoto navel to Washington navel, the industry 

standard, and to Clemenules mandarin on various rootstocks 

under three irrigation regimes and in a neutral and high pH 

soil. Growth characteristics measured included production of 


Five-year-old Fukumoto navel on C-35 rootstock at 

LREC showing continued proliferation of suckers 

and watersprouts. White patches above and below 

the graft union are areas of bark and underlying 

wood removed for carbohydrate testing. Picture 

taken December 11, 2009. 

water sprouts on the scion within 

four inches of the graft union, and 

suckers on the rootstock between 

ground level and the graft union, 

scion and rootstock diameter two 

inches above and below the graft 

union, tree height (from ground 

level to the highest point of vegetation 

on the tree), and some limited 

midday shaded leaf-water potential 

measurements and carbohydrate 

analyses from trunk cores taken 

above and below the graft union. 

Irrigation experiment at the 

UC Lindcove Research and 

Extension Center (LREC) 

An experiment was established 

at the LREC in July 2004, after 

fumigation of the experimental 

site that spring with methyl bromide. 

The source of the Fukumoto 

budwood was from registered 

trees at LREC. This replicated and 

randomized experiment compared 

various growth characteristics 

between Fukumoto navel, Clemenules 

mandarin and Washington 

navel on four different rootstocks 

(rough lemon, C-35, Carrizo and 

Valencia/Carrizo interstock), under three different irrigation 

regimes (including under- and over-watering of Fukumoto 

navel). 

The three irrigation treatments were referred to as low, mid 

and high. In 2008, the low and high water application rates were 

66% and 299% of the mid level (100%), while in 2009 the low 

and high were 38% and 273% of the mid level respectively. 

Differential irrigation rates were applied using both different 

numbers of drip emitters (Bowsmith ® ) per tree and emitters 

with different flow rates. The duration of irrigation remained 

constant for all irrigation treatments. Irrigations were applied 

when soil moisture tension in a sensor (Watermark ® ), set at 

16 inches below ground level in the root zone of a Fukumoto 

navel on Carrizo rootstock in a “mid-level” irrigation treatment, 

measured -50 centibars. 

The poor performance of the rootstock ‘rough lemon’ 

for all cultivars was unlike that seen in growers’ fields. The

poorer growth of trees on this rootstock in our experiment 

was probably a result of not removing the prolific growth of 

rough lemon rootstock suckers often enough for adequate 

growth of the scion. Suckers were removed twice yearly from 

the trees in the experiment at LREC. For this reason, data 

collected with rough lemon was excluded from some of the 

analyses. Washington navel had a greater scion diameter in 

2008 (Table 1) than Fukumoto at the high irrigation level. 

The rate of increase of scion diameter for Washington navel 

in the high irrigation treatment on Carrizo and C35 citrange 

rootstocks over the course of the experiment was greater 

than for Fukumoto navel (Fig. 1). Scion diameter on Carrizo 

and C-35 rootstocks increased with increasing irrigation for 

both Clementine and Washington navel (Table 1). Fukumoto 

scion diameter did not respond to increasing levels of irrigation 

(Table 1) demonstrating that for trees of equal age, 

Fukumoto may require less irrigation thanWashington navel 

or Clementine mandarin. 

Soil pH experiment at the UC Kern County Cooperative 

Extension Office, Bakersfield 

A second experiment was established in June 2005 located 

at the University of California Kern County Cooperative 

Extension Office in Bakersfield (UCCE Kern). Budwood 

Table 1. Scion diameter for Clemenules mandarin, Fukumoto 

and Washington navel in 2009 under three irrigation regimes 

averaged across performance on C35, Carrizo and an 

interstock of Olinda Valencia on Carrizo rootstock at LREC. 

Scion diameter (mm) 

for three irrigation treatments 1 

Variety Low Mid High 

Clemenules mandarin 63.6aA 70.8aA 75.4abB 

Fukumoto navel 64.7aA 69.8aA 66.3aA 

Washington navel 70.3aA 73.4aA 85.3bB 

1 

Values in each column followed by different lower case letters (comparing 

varieties) and values in each row followed by different upper case letters 

(comparing irrigation) are significantly different according to Fisher’s 

protected LSD test (P ≤ 0.05) 

Scion Diameter, mm 

100 

80 

60 

40 

20 

0 

Fukumoto 

Washington 

2004 2005 2006 2007 2008 

Fig. 1. Differences in scion diameter with time between 

Washington and Fukumoto navel in trees grown on Carrizo 

and C-35 rootstocks in the highest irrigation treatment at 

LREC, 2008. 

Table 2. Percentage of the total number of Clemenules, 

Fukumoto or Washington navel trees with the ratio of 

the scion diameter to rootstock diameter less than 0.70 

or 0.60 at LREC, 2008. 

Cultivar/Rootstock Percentage of Percentage of 

trees < 0.70 trees < 0.60 

Clemenules/Carrizo 0 0 

Clemenules/C35 41.6 0 

Fukumoto/Carrizo 0 0 

Fukumoto/C35 33.3 16.7 

Washington/Carrizo 0 0 

Washington/C35 8.3 0 

Table 3. The effect of cultivar on average scion diameter 

and the ratio of the scion diameter to rootstock diameter 

for individual potted navel trees on Carrizo rootstock, 

UCCE Kern, 2008. 

Cultivar 1 

Trunk characteristic Fukumoto Washington 

Scion diameter 2 (mm) 33.0a 42.8b 

Scion/rootstock ratio 0.65a 0.78b 

1 

Values in each row followed by different letters are significantly different 

according to Fishers’s protected LSD test (P m 0.05). 

2 

Measured 2 inches above the graft union. 

Average number of suckers and water sprouts 

16 

14 

12 

10 

8 

6 

4 

2 

0 

2004 2005 2006 2007 2008 2009 

Fukumoto/C-35 

Fukumoto/Carrizo 

Fukumoto/Valencia/ 

Carrizo 

Washington/C-35 

Washington/Carrizo 

Fig. 2. Average number of suckers and water sprouts per tree 

per year at LREC. For Year 2009, the total is as of June 11. 


and trees were obtained from a private 

nursery. Similar growth characteristics to 

those measured at LREC were monitored 

on Fukumoto and Washington navel trees 

on Carrizo rootstock, planted in large 

20-gallon pots that contained either neutral 

(pH approximately 6.5 to 7) or alkaline 

soil (pH 8.0 or greater}. Pots were acidified 

with soil sulfur or made more alkaline 

with hydrated lime. Soil samples from the 

pots were analyzed by the Agriculture and 

Natural Resources laboratory at University 

of California Davis. Measurements 

associated with pH, such as available zinc, 

iron, copper, manganese, calcium, sulfates, 

carbonates, electrical conductivity, and 

other compounds were also tested in the 

soil and in leaves. 

Sum of suckers and water sprouts 

40 

30 

20 

10 

Tree 8 

Tree 21 

Tree 26 

Tree 39 

Tree 55 

Tree 66 

Tree 73 

Tree 90 

Tree 108 

Tree 119 

Tree 128 

Tree 141 

Effect of irrigation and soil pH 

on Fukumoto decline 

The level of irrigation and soil pH 

achieved in these LREC and UCCE 

Kern experiments did not produce any 

severe decline symptoms or any measured 

growth characteristic in the Fukumoto 

trees. Drought stress, though, was clearly 

evident between irrigations in all varieties in the treatment 

receiving the lowest irrigation application rate in 2007, 2008 

and 2009, and leaf yellowing and early leaf drop was evident 

in the alkaline pots. Poorly performing Fukumoto trees were 

present in both experiments, but they appeared randomly 

across all irrigation treatments and in pots with both neutral 

and basic soil pH. Fukumoto trees on citrange rootstocks (i.e. 

Carrizo and C-35) were more likely to be stunted as reflected 

in their smaller scion diameters and reduced ratio of scion 

diameter to rootstock diameter (Tables 2 and 3). Fukumoto 

Average number of suckers and water sprouts per tree 

14 

12 

10 

8 

6 

4 

2 

0 

2005 2006 2007 2008 2009 


Fukumoto/Carrizo 

Washington/Carrizo 

Fig. 3. Average number of suckers and water sprouts per 

Fukumoto or Washington navel tree per year on Carrizo 

rootstock in large pots at UCCE Kern. For Year 2009, the total 

is as of June 18. 

0 

2004 2005 2006 2007 2008 2009 

Fig. 4. Annual total number of suckers and water sprouts for each Fukumoto 

tree on C-35 rootstock in the LREC trial (identified by position in the trial 

regardless of irrigation treatment). For Year 2009, the total number of sprouts 

is as of June 11. 

trees were also more likely to produce large numbers of 

suckers (sprouts produced below the graft union) and water 

sprouts (scion sprouts produced within four inches of the graft 

union) compared to Washington navel at LREC (Fig. 2) and 

UCCE Kern (Fig. 3). Production of large number of suckers 

and water sprouts in many tree crops has been considered 

a sign of incompatibility of the scion with the rootstock but 

may be caused by other factors as well. This excessive sprout 

production is characteristic of many trees in most Fukumoto 

orchards. Fukumoto on C-35 rootstock, generally, demonstrated 

more sprout production and a smaller scion/rootstock 

diameter ratio than did Carrizo (Table 2 and Fig. 2) 

Differential sucker and water sprout production between 

Fukumoto and Washington navel did not begin to occur at 

LREC until the third year of the trial (Figures 2 and 4). Citrus 

trees growing in the 20-gallon pots of the UCCE Kern experiment 

were usually under considerably more transient water 

and salt stress than those growing in the ground because of 

a poorer soil water storage reservoir and poorer drainage. In 

UCCE Kern, unlike the trial at the LREC, differential sucker 

and water sprout production between Fukumoto and Washington 

navel was observed during the first year of the trial (Fig. 

3). The average values shown in the tables and figures tend 

to minimize the actual differences seen in the experimental 

plots or pots between the best and poorest performing Fukumoto 

navels for all measured growth characteristics. For 

example, the number of suckers produced by a given Fukumoto 

tree varied considerably (Fig. 4). Note, also, that trees 

that produced excessive sprouts at an early age continued 

producing high numbers of sprouts as they grew older even 

though the trunks were shaded by the leaf canopy. Variable 

performance of individual Fukumoto trees within a grower’s 

field is commonly observed in commercial orchards as well. 

Why some Fukumoto trees perform similarly to Washington

navel on the citrange rootstocks and others perform poorly 

remains unknown. 

Ants were present in the LREC test plot in 2006, and their 

presence was associated with tree trunk gumming. In some 

Fukumoto trees, the gum was frothy, with small branches 

breaking at their attachments to the larger scaffolds as occurs 

with foamy bark rot. Twenty-four percent of Fukumoto 

navel trees were exuding gum, compared to only 9 and 1% 

of Washington navel and Clemenules mandarin, respectively, 

suggesting Fukumoto navels produce more gum and so are 

more attractive to ants. Observationally, the gumming in 

Fukumoto not only occurred under the tree wrap as in the 

other two varieties, but commonly higher on the scaffolds and 

in the leaf canopy. 

At LREC, Fukumoto fruit yields in 2007 and 2008, the 

only years measured, were not significantly different among 

the four rootstocks (data not shown), although with time 

the stunted trees would probably fall behind the vigorously 

growing trees. No late-maturing or off-type fruit was observed 

in the trials. Differences were not found among cultivars 

and rootstock combinations for midday leaf water potential 

made in June and July of 2006 at LREC, or for differences 

in starch accumulation above the graft union among the 

best-performing or worst-performing Fukumoto trees made 

in December 2009. Accumulation of starch above the graft 

union may have been indicative of graft union incompatibility; 

however, profuse sprout production below the graft 

union may have been sufficient to mask lack of translocation 

through the graft union. 

Application of research results for 

Fukumoto navel growers 

The cause of Fukumoto tree decline remains unknown, 

and scion-rootstock incompatibility remains a possibility. 

Based on the results from this project, the following suggestions 

are made for growers planting or that currently are 

cultivating immature blocks of Fukumoto navels: 

• Extra effort in identifying and eradicating southern fire 

ant infestations is warranted. 

• Growers accustomed to growing other navel cultivars, 

such as Washington navel, may find for similarly aged trees 

under similar environmental conditions that Fukumoto navel 

may require less water than Washington navel as a result of 

a smaller canopy. 

• More frequent passes through the orchard to remove 

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suckers and watersprouts will be required, especially beginning 

in the third year after planting, and earlier, if grown under 

stressful conditions. 

• Fukumoto on Carrizo rootstock, generally, will produce 

fewer suckers, watersprouts and stunted trees than on C-35, 

although both rootstocks have been associated with severe 

decline in some orchards. 

• Early replacement of stunted trees that have both excessive 

sucker scars and small diameter scions compared to the 

rootstock appears advisable. 

Future plans involving collaboration and 

utilization of research results 

In cooperation with Dr. Georgios Vidalakis of the 

California Citrus Clonal Protection Program (CCPP), we 

have plans to put the information that we have gathered 

to further use. Our results suggest that the current source 

of Fukumoto budwood may not be as compatible with 

our commonly used trifoliate and citrange rootstocks as is 

Washington navel. Spanish researchers have reported that 

they have not had problems with Fukumoto on Carrizo 

such as those observed by California growers. Dr. Vidalakis 

has obtained budwood of Fukumoto navel from a Spanish 

source and has ensured that it is free of disease by passing 

it through the CCPP cleanup program. Fukumoto trees on 

Carrizo rootstock grown from the existing California source 

of Fukumoto budwood and from the new Spanish source 

will be compared with LREC Fukumoto budwood. This trial 

was planted in May of 2010 on the property of a commercial 

citrus grower where previous plantings of Fukumoto navel 

have demonstrated high rates of stunting and suckering. As a 

result of the current project, we have identified the following 

measurable characteristics that will be used to determine if 

the new budwood source is different from the existing source 

when grown on citrange rootstocks: 

1. The number of water sprouts produced within four 

inches of the graft union and all suckers on the rootstock. 

2. The percentage of two-year-old trees showing stunting, 

typified by smaller scion diameters, and scion diameter/rootstock 

diameter ratios less than 0.70 and especially less than 0.60. 

The comparisons will continue until the trees begin to 

produce fruit to ensure that the fruit has a similar maturity 

date to the existing Fukumoto navel line. Since differences in 

irrigation or soil pH within the ranges of these experiments 

did not appear to affect the growth of Fukumoto navel, these 

environmental variables do not need to be included in the 

future bud source evaluation trial. If trees from the Spanish 

budwood source demonstrate growth characteristics similar 

to the Washington navel trees evaluated in this project and 

less like the Fukumoto trees from the existing budlines in the 

Foundation Block at LREC, then the budwood will likely be 

replaced with the Spanish line. 

Additionally, new methods of detecting diseases in citrus 

have been developed by researchers with Citrus Research 

Board funding. Again, while not part of this project, samples 

from declining and good performing Fukumoto trees will be 

collected and evaluated for foreign DNA, which, if found, may 

suggest that the decline is caused from a previously undetected 

disease agent. l 

Project Leader Craig E. Kallsen is Farm Advisor, 

University of California Cooperative Extension Kern 

County, and Co-Project Leader Neil V. O’Connell is Farm 

Advisor, University of California Cooperative Extension 

Tulare County. 

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mcsales@delite.com 

mulhollandcitrus.com 



Citrus Quarantine, Sanitary, and 

Certification Programs in the USA 

Prevention of Introduction and 

Distribution of Citrus Diseases 

Part 1 — Citrus quarantine and introduction programs 

Georgios Vidalakis 1 , John V. da Graça 2 , Wayne N. Dixon 3 , Donald Ferrin 4 , Michael Kesinger 5 , 

Robert R. Krueger 6 , Richard F. Lee 6 , Michael J. Melzer 7 , John Olive 8 , MaryLou Polek 9 , 

Peggy J. Sieburth 5 , Lisa L. Williams 10 , and Glenn C. Wright 11 

Editor’s Note: This is Part 1 of a 

two-part article discussing the 

major USA citrus germplasm 

programs and other national efforts 

to harmonize the protocols for citrus 

germplasm movement. This first part 

describes the different citrus quarantineintroduction 

programs of the USA. Part 

2, which is scheduled for the next issue, 

will describe the different certification 

schemes as well as national efforts and 

programs for citrus propagative material. 

Background 

Citrus germplasm originated in 

Australasia, the Far East, and Africa; 

thus all citrus grown in the New World 

was imported. This importation of citrus 

also resulted in importation of grafttransmissible 

pathogens of citrus capable 

of causing destructive epidemics such 

as the 1930-1960 tristeza quick decline 

that killed more than 60 million trees 

worldwide. One of the main reasons 

for the citrus industry’s survival and 

prosperity through the decades is the 

early establishment of citrus germplasm 

programs, such as California’s Citrus 

Clonal Protection Program, that provide 

a safe mechanism of introduction of new 

varieties via disease testing and therapy 

and distribution of high-quality diseasetested 

citrus propagative materials. 

Introduction 

Citrus germplasm has moved from 

its geographic origin in the Australasia 

(Pangea, c. 20 Ma), Far East, and Africa, 


bringing with it graft-transmissible diseases 

to all the citrus growing areas of 

the world. In spite of the plethora of such 

diseases, the citrus industry has survived 

through the decades and prospered in 

many countries including the USA. This 

is a direct result of the establishment of 

citrus germplasm programs that provide 

a safe mechanism of introduction 

of new varieties via disease testing and 

therapy and that distribute high-quality 

disease-tested propagative material to 

the industry. 

The basic protocols for the detection 

and elimination of graft-transmissible 

pathogens of citrus are well defined and 

have been known for many decades. 

Similarly, the budwood distribution 

mechanisms with disease re-tested 

mother trees, increase blocks, and fruit 

evaluation for horticultural truenessto-type 

are also well defined and in use 

in many citricultural countries around 

the world. 

In the USA, the main citrus producing 

states are California, Arizona, Texas 

and Florida. Even though the protocols 

and technology for the citrus germplasm 

programs are common across the board, 

each of these states has developed and 

adjusted their quarantine-introduction 

and budwood distribution-certification 

programs to the needs (size, type, available 

resources, involved agencies, disease 

or pest pressures etc) of their specific 

industries. 

In California, the Citrus Clonal Protection 

Program handles the majority of 

quarantine-introduction and budwood 

distribution-certifications. In Florida, 

two different programs – the Citrus 

Germplasm Introduction Program and 

the Bureau of Citrus Budwood Registration 

– handle the quarantine-introduction 

and budwood distribution-certification, 

respectively. Arizona and Texas 

do not have a quarantine-introduction 

program. They acquire pathogen tested 

citrus budwood from California and 

Florida, and they maintain, re-test and 

distribute budwood to their industries 

via distribution-certification programs, 

namely the Arizona Certified Budwood 

Program and the Texas Citrus Budwood 

Certification Program. 

Overall, the different USA programs 

presented here involve multiple agencies 

or entities (university, state and federal 

government, and industry) in order to 

have the necessary funds, scientific 

knowledge, infrastructure, and regulatory 

basis for successful operation. 

In the United States, the USDA-ARS 

National Clonal Germplasm Repository 

for Citrus and Dates (NCGRCD), while 

based in California, actually serves the 

entire USA and distributes materials 

free of charge to qualified scientists 

and certification programs around the 

globe. The NCGRCD is not focused 

only on citrus varieties with commercial 

interest, like most of the state operating 

programs, but it also preserves, in general, 

the germplasm of citrus and citrus 

relatives. 

The control of graft-transmissible

diseases of citrus is based primarily on 

preventative measures. The most important 

one is the use of healthy propagating 

material through strict quarantine 

and the implementation of in-country 

certification schemes for the provision of 

adequate supplies of disease-tested, trueto-type 

citrus germplasm. In the USA, 

such programs started approximately 60 

years ago in the main citrus-producing 

states. Today, California, Arizona, Texas, 

Louisiana, Alabama, Florida and Hawaii 

have developed, or are in the process of 

developing, different citrus quarantineintroduction 

and budwood-certification 

programs adjusted to the needs of their 

citrus industries based on the type (e.g., 

fresh fruit, juice, ornamental), size, 

available resources, growing conditions, 

disease and pest pressures, and participants 

or collaborators (state, federal, 

university, private etc.). 

California 

The California Citrus Clonal Protection 

Program (CCPP) has its roots in the 

1930s when the original discovery of the 

viral nature of the graft-transmissible 

disease citrus psorosis by Dr. H. Fawcett 

at the University of California Citrus 

Experiment Station in Riverside triggered 

the establishment of the “Psorosis 

Free Program.” The CCPP was officially 

established in 1956 as the “Citrus Variety 

Improvement Program (CVIP)” after 

the request of the citrus industry to the 

University of California. 

In 1977, the CVIP was restructured 

and renamed to CCPP and today stands 

as a cooperative program between 

the University of California Riverside 

(UCR, Department of Plant Pathology 

& Microbiology), the California Department 

of Food and Agriculture (CDFA), 

the United States Department of Agriculture’s 

Animal and Plant Health 

Inspection Service (USDA-APHIS), 

and the citrus industry of the state of 

California represented by the California 

Citrus Nursery Board (CCNB) and the 

Citrus Research Board (CRB). 

The CCPP has a staff director, three 

staff research associates, and one to three 

nursery technicians and operates at three 

locations: the Rubidoux Quarantine Facility 

in downtown Riverside, the Citrus 

Diagnostic Laboratory on the UCR 

campus, and the Foundation and Evaluation 

Blocks at the Lindcove Research 

and Extension Center (LREC), Exeter, 

CA. The CCPP is supported almost 

exclusively by the CRB (a grower’s box 

tax research marketing order founded 

in 1968) while UCR offers infrastructural 

support and scientific expertise. The 

CCNB contributes to the CCPP operations 

via the program of “Cooperative 

Registration Testing of Nursery Owned 

Citrus Scion and Seed Source Trees”. A 

committee of approximately 12 industry 

members (growers and nurserymen) 

supports the CCPP activities. 

The purpose of the CCPP is to provide 

a safe mechanism for the introduction 

into California of citrus varieties 

from any citrus-growing area of the 

world for research, variety improvement, 

or for use by the commercial industry of 

the state. The introduction mechanism 

includes disease diagnosis and pathogen 

elimination followed by maintenance 

and distribution of true-to-type primary 

citrus propagative material of the commercially 

important scion and rootstock 

varieties. We will describe these functions 

in detail only for the CCPP since 

in principal they are used in all the other 

programs described here. 

A. Introduction of citrus varieties under 

quarantine 

The citrus quarantine in California 

is a cooperative venture involving federal, 

state, and county departments of 

agriculture and the University of California 

(UC). The federal government 

represented by the USDA-APHIS-PPQ 

(Plant Protection and Quarantine) is 

concerned with citrus pest exclusion 

from foreign sources entering the U.S. 

There are also instances where federal 

quarantines exist between states, which 

likewise govern the movement of citrus. 

The director of the CCPP has a 

USDA-APHIS-PPQ issued permit to 

import citrus budwood from foreign 

countries (one of the only three permits 

for citrus introduction into the USA). 

There are specific stipulations spelled 

out on this permit regarding handling 

and treatment of materials in quarantine 

which must be followed when citrus 

material enters the Riverside CCPP 

Quarantine Facilities at Rubidoux. These 

stipulations are also required by the 

State of California and are enforced by 

the CDFA. The State of California Agricultural 

Code (Cal. Admin. Code tit. 3, 

§ 3250 Citrus pests exterior quarantine) 

clearly states that all citrus budwood is 

prohibited from entry into California 

unless authorized under a CDFA and/ 

or USDA permit such as the one issued 

to the CCPP director. 

All citrus germplasm entering the 

USA first goes through the federal quarantine 

facility in Beltsville, Maryland. 

Upon arrival, the budwood is visually inspected 

for the presence of insect, fungal 

Fig.1. The Citrus Clonal 

Protection Program 

quarantine facilities at the 

University of California 

Riverside. Glasshouse for 

the biological indexing of 

graft-transmissible diseases 

of citrus (A), screenhouse 

for the maintance of the 

positive control collection 

and the production of 

field trees (B), laboratory 

for diagnostics and the 

therapeutic protocols 

(C), the interior of the 

screenhouse with field trees 

(D), and the interior of the 

glasshouse with different 

developmental stages of 

citrus bio-indicators (E). 


California Citrus Clonal Protection Program 

Variety Introduction Scheme 

Month 1 1) INTRODUCTION OF BUDWOOD 

1A) PRE-INDEX 1B) PRIMARY INCREASE 

Budwood is imported under quarantine according 

Month 6 Mexican Lime, sweet orange, to the stipulations of the Federal importation Four source trees are made 

and Etrog citron are graft- permit of the CCPP Director. with the introduced budwood grafted 

inoculated with the introduced Pre-index (1A) and primary onto rough lemon rootstocks. 

budwood for the detection of increase trees (1B) start simultaneously. Budwood is also cultivated in vitro 

tristeza, psorosis, and citrus viroids. 

for micro-grafting. 

2) THERAPY 

2A) SHOOT-TIP-GRAFTING Graft-transmissible diseases 2B) THERMAL THERAPY 

detected in the pre-index (1A) are 

eliminated by shoot-tip-grafting 

(2A) and/or thermal therapy (2B). 

The use of both methods 

Month 12 

of therapy add approximately 

one year more to the quarantine time. 

Shoot-tip-grafting is effective in 

eliminating graft-transmissible 

disease agents, including viroids. 

Thermal therapy is effective in eliminating graft-transmissible 

disease agents except for viroids. All introductions of origin outside of 

California go through Thermal therapy as a precautionary measure. 

Month 18 3) INDEX OF THERAPY PROPAGATION 

Budwood is graft-inoculated onto 

indicator plants (as in 1A) to determine 

if pathogens detected during pre-index 

have been eliminated. 

3A) THERAPY SUCCESS 3B) THERAPY FAILURE 

Index negative for graft-transmissible 

Index positive 

diseases the introduction enters 

for diseases. 

Month 24 into the Variety Introduction (VI) Index. (Return to Step 2) 

4) VARIETY INTRODUCTION (VI) INDEX 

Month 30 

The VI Index begins in the fall of each year and it lasts approximately 12 months and includes bio-indexing onto a 

host range of some 60 indicator seedlings including a broad range of negative and positive disease controls 

(mild, moderate, and severe isolates) and laboratory testing (i.e. ELISA, sPAGE, PCR, and culturing). After a variety introduction 

tests negative for all graft-transmissible diseases in the VI Index, budwood source trees are produced in quarantine for field planting. 

5) QUARANTINE RELEASE 

Month 36 

Fig. 2. Procedure 

and timeline for the 

introduction of new 

varieties (including 

proprietary varieties) 

into California via the 

Citrus Clonal Protection 

Program (CCPP). 

CCPP must apply to the California Department of Food and Agriculture (CDFA) and the United States Department of Agriculture (USDA) 

for State and Federal Quarantine Releases. With quarantine release CCPP is permitted to move budwood source trees 

from quarantine in Riverside to the Lindcove Foundation Block for budwood distribution to the industry and researchers. 


pests or other potentially bio-hazardous 

materials (e.g. soil). It is then sent to the 

CCPP Rubidoux Quarantine Facility in 

Riverside. The Rubidoux Facility consists 

of approximately 5,000 sq. ft. (~450 

m 2 ) of insect-proof greenhouse with 

temperature and light controls that are 

required for biological indexing, 9,000 

sq. ft. (~850 m 2 ) of screenhouse, and a 

modular office and laboratory area. The 

Rubidoux Quarantine Facility is located 

within the city of Riverside adjacent 

to the original location of the Citrus 

Experiment Station (1907) and isolated 

from the nearest commercial citrus and 

University experimental orchards by 

about 3 miles (~5 km) (Fig. 1). The CCPP 

quarantine and campus laboratory facilities 

are part of the space allocated by the 

Department of Plant Pathology & Microbiology 

of the College of Natural and 

Agricultural Sciences in the University 

of California Riverside. 

Typically, when a new import is received 

by CCPP at the Rubidoux Quarantine 

Facility, propagations are made 

onto rough lemon rootstocks to preserve 

the budline and to produce budwood 

for future index and/or therapy. These 

propagations are placed in a warm 

greenhouse for maximum and rapid 

growth. In addition, some of the imported 

budwood is cultured in vitro and the 

meristems of the produced young flushes 

are used for in vitro micro-propagations 

following the “shoot-tip-micrografting” 

procedure. The remaining portion of 

the original imported budwood is used 

to graft inoculate indicator seedlings 

in a screening index called a pre-index. 

Disease symptoms in the pre-index plant 

indicators will indicate if the import 

budline is infected with tristeza virus, 

vein enation virus, psorosis and psorosisrelated 

pathogens or citrus viroids (Fig. 

2, 1A & B). A very high percentage 

of newly imported budwood arrives 

infected with one or more of these budtransmissible 

diseases. 

B. Disease diagnosis - Pathogen detection 

The CCPP program of importation, 

production and distribution of diseasefree 

propagative materials is based on 

a comprehensive indexing, or testing, 

program to detect graft-transmissible 

diseases, which may arrive in an imported 

budline. Graft-transmissible diseases 

may be caused by viruses, viroids or other 

pathogens (bacteria, phytoplasmas) 

and are vegetatively transmitted with 

an infected budline. Graft-transmissible 

diseases can seriously affect fruit quality, 

production, tree health and longevity. 

Additionally, diseases from infected field 

propagations may be spread to neighboring 

orchards of healthy trees by insects 

or farming equipment. 

Detection of graft-transmissible diseases 

of citrus is based primarily upon 

biological indexing, which is accomplished 

by grafting tissue of the imported 

budline onto citrus indicator seedlings. 

Specific indicator seedlings are used to 

detect specific diseases. Indicator varieties 

have been selected for sensitivity to 

diseases and ability to express symptoms. 

In each index, adequate positive controls, 

or disease-infected seedlings along with 

healthy control seedlings of each indicator 

variety, are held under the same environmental 

conditions as test seedlings. 

Controls are used as a comparison with 

the test source and also as confirmation 

Fig. 3. Biological indexing of graft-transmissible diseases of citrus. Young growth 

of plant indicator (approx. 4-6 weeks post inoculation) will be observed for 10- 

12 months for symptom development (A), graft inoculation of plant indicator (B). 

T-cut and budwood chip (inoculum) insertion (B i), wrapping with budding tape 

(B ii), and healing with alive inoculum, 3-4 weeks later (B iii). Reactions of citrus 

bio-indicators on wood (C), branches (D), and leaves (E). 

(C) Wood of healthy citrus (C i), gumming and wood coloration reaction of 

Pearson’s special mandarin to the cachexia viroid (C ii), and stem pitting reaction 

of sweet orange to the tristeza virus (C iii). 

(D) Branch of healthy citrus (D i), severe leaf epinasty reaction of Etrog citron 

Arizona 861-S-1 to the exocortis viroid (D ii), leaf bending and mild leaf epinasty 

of Etrog citron Arizona 861-S-1 to the bent leaf viroid (D iii), leaf drooping 

reaction of Etrog citron Arizona 861-S-1 to the dwarfing viroid (D iv), stem, 

petiole, and mid vein necrosis reaction of Etrog citron Arizona 861-S-1 to mixed 

infection of citrus viroids (D v), leaf cupping reaction of Mexican lime to the 

tristeza virus (D vi), shock reaction of Dweet tangor to the psorosis virus (D vii), 

and leaf curling and chlorosis of lemon due to fetal yellows disease (pathogen 

unknown) (D viii). 

(E) Leaf of healthy citrus (E i), corky vein reaction to the tristeza virus (E ii), leaf 

deformation reaction of sour orange to the infectious variegation virus (E iii), 

yellow vein reaction of Etrog citron Arizona 861-S-1 due to yellow vein disease 

(pathogen unknown) (E iv), tatter leaf reaction of Carrizo citrange to the tatter 

leaf virus (E v), young leaf pattern reaction of Dweet tangor to the leaf blotch 

virus (E vi), vein clearing (E vii) and water soaked (E viii) reaction of the top and 

lower part of a Mexican lime leaf respectively to the tristeza virus, vein enation 

reaction of Mexican lime due to vein enation disease (pathogen unknown) (E ix). 


that environmental conditions in the 

greenhouse are optimal for plant growth 

and symptom expression (Fig. 3). 

Laboratory tests are also part of the 

disease diagnosis process. Examples of 

complementary laboratory techniques 

to the biological testing are the enzyme 

linked immunosorbent assay (ELISA) 

used for the detection of the tristeza 

virus; sequential polyacrylamide gel 

electrophoresis (sPAGE), polymerase 

chain reaction (PCR); and hybridization 

used for the detection of citrus viroids; 

and culture in growth media used for the 

detection of Spiroplasma citri, the causal 

agent of citrus stubborn disease (Fig. 4). 

Pathogen detection or indexing 

occurs at different times and steps of 

the introductory procedure. One small 

scale testing (pre-index) takes place at 

the time of introduction (see section 

A) (Fig. 2, 1A & 1B). The results of the 

pre-index indicate the need and type of 

therapy necessary (see section C) (Fig.2, 

2A & 2B). The success of the therapy 

is assessed by another small scale preindexing 

(biological and/or laboratory 

testing) (Fig. 2, 3A & 3B). If all results 

indicate that therapy was successful, then 

the budline enters a full scale VI index. 

The VI testing lasts approximately 12 

months and includes bio-indexing onto a 

host range of some 60 indicator seedlings 

including a broad range of negative and 

positive disease controls (mild, moderate, 

and severe isolates) and laboratory 

testing (i.e. ELISA, sPAGE, PCR, culturing) 

(Fig.2, 4 and Fig. 3 and 4). 

C. Pathogen elimination-Therapy 

If the introductory pre-index indicates 

the presence of disease(s) or 

pathogen(s), the budline must be subjected 

to therapy procedures that can 

eliminate the disease(s) agent(s). The 

CCPP employs two methods of therapy: 

thermaltherapy (aka thermotherapy), 

and shoot-tip-micrografting (Fig. 2, 

2A & 2B). UCR and CCPP have been 

instrumental in the development, validation 

and employment of both techniques 

since the early 70s. 

Thermaltherapy or heat treatment 

is performed by taking buds from the 

infected budline and grafting them 

onto citrange (sweet x trifoliate orange) 

seedlings. The infected bud grafted onto 

each seedling is tightly and completely 

wrapped with budding tape so that the 

bud will not flush during thermaltherapy. 

The citrange seedlings, each with an 

infected bud grafted on it, are placed 

into a hot greenhouse with temperatures 

maintained at 28-40°C daytime and 25°C 

nighttime for preconditioning to high 

temperatures for 30 days. Following 

preconditioning, the seedlings are placed 

into a controlled temperature chamber 

which is set for 16-hour days at 40°C 

and 8-hour nights set at 30°C. Plants 

are maintained in the thermaltherapy 

chamber for a period of 3 months. 

Upon removal of the plants from 

the temperature chamber, the buds are 

unwrapped (Fig. 5). The rootstock seedling 

is lopped over, and the top of the 

seedling is pushed into the potting soil 

such that the grafted bud will become 

the terminal bud. The plants are then 

placed in the greenhouse until sufficient 

budwood growth is produced from the 

Fig. 5. Thermal therapy heat chamber. 

Fig. 4. Citrus Clonal Protection Program laboratory 

diagnostic techniques for graft-transmissible 

pathogens of citrus. Enzyme-linked immunosorbent 

assay (ELISA) microtiter plate reader (A) and plate 

with yellow positive reactions (B), ethidium bromide 

stained agarose gel under ultraviolate light for 

the visualization of DNA products of conventional 

polymerase chain reaction (PCR) (C), quantitative 

real time PCR equipment (D), silver stained gel 

after sequential polyacrylamide gel electrophoresis 

(sPAGE) for the detection of viroid and viroid-like 

RNA molecules (E), hybridization against DIG-labeled 

probes for the detection of viral nucleic acids (F), and 

microscopic observation of culture of prokaryotic 

pathogens (in this case Spiroplasma citri) (G). 


grafted bud for further indexing. This 

method is effective against most citrus 

viruses; however, is not effective against 

viroids, and its effect on citrus tatter leaf 

virus has been reported to be variable. 

All imports received by CCPP originating 

outside the U.S. are routinely subjected 

to thermaltherapy as a precaution. 

Shoot-tip-micrografting (STG) is the 

other form of disease clean-up therapy 

employed by the CCPP. Some pathogens, 

particularly the citrus viroids (e.g. 

exocortis, cachexia), are difficult or impossible 

to eliminate by thermaltherapy 

and are much more readily eliminated by 

STG. STG is a procedure where several 

new growth tips slightly less than 1cm in 

length are taken from one of the original 

infected import propagations. Under a 

dissecting microscope, an apical meristem 

of about 0.15 mm, barely visible 

to the naked eye, is removed from the 

infected growth tip and grafted onto a 

seedling grown in vitro. If small enough 

when removed from the growth tip, the 

apical meristem is not yet developed 

enough to contain the pathogen, and 

therefore the disease will not be present 

in the micro-grafted propagation. STG 

propagations are returned to glass tubes 

and placed under light in a culture chamber. 

When the scion of the micrografted 

propagation reaches about 2 cm, it is regrafted 

onto a clean rough lemon seedling 

and moved to the greenhouse. STG 

is effective against all graft-transmissible 

agents including viroids (Fig. 6). 

The two therapy techniques – thermotherapy 

and shoot-tip-grafting – are 

complimentary, providing a flexible system 

for pathogen elimination bypassing 

the limitations (thermotherapy ineffective 

for viroids) and/or practical restrictions 

(STG long growth-regeneration 

time, specialized equipment, in vitro 

contaminants, and possible rootstockscion 

incompatibilities) that one method 

may have. 

Following any therapy procedure, all 

propagations produced during therapy 

must go through indexing again to determine 

their disease status. If the subsequent 

indexing indicates that a disease is 

still present, then the plant material must 

be subjected again to therapy. This cycle 

of therapy and testing continues until all 

tests are negative. When propagation of 

a budline tests negative in a pre-indexing 

following therapy, it may then enter the 

full scale VI index (see section B) (Fig.2, 

4). If a budline is shown to be free of 

Fig.6. Shoot-tip-grafting. Preparation of shoot tip from the source plant (A i) and 

excision of apical meristem (2-3 leaf primordia barely visible with naked eye) (A 

ii). Preparation of rootstock seedling, seed germination in vitro (B i) and removal 

of portion of shoot and root growth (B ii). Necessary tools (scalpels, scissors, 

and forceps) for shoot-tip-grafting (C i) and dissecting microscope (C ii). Inverted 

T-cut on rootstock seedling under the dissecting microscope and placement of 

the apical meristem in contact with cambial tissue ((D I and ii). In vitro growth 

of shoot-tip grafted plants in liquid media (E i) and apical meristem growth after 

shoot-tip-grafting (E ii). 

known diseases in the VI Index, it is 

then considered ready for release from 

quarantine (Fig.2, 5) (see section D). 

D. Quarantine release 

When an introduced budline has 

tested negative for all known budtransmissible 

diseases in the VI index, 

the CCPP then applies for its release 

from both state and federal quarantine. 

The CCPP must first obtain release from 

CDFA by outlining the testing procedures 

and test results. Once released by 

the State of California, an application 

for federal quarantine release is sent to 

USDA/APHIS containing the testing 

information and a copy of the letter of 

approval by the State of California for 

release from quarantine. The distribution 

of citrus material that has been released 

from quarantine is also a highly regulated 

and carefully executed procedure 

that involves close interaction between 

CDFA, CCPP, and citrus nurserymen 

and growers (Fig. 2, 5). 

The above described introductory 

procedure and release from quarantine 

is available to private entities that 

wish to import patented or other proprietary 

varieties into California. The 

propagator/owner signs an agreement 

with UCR for the recovery of the cost 

of the testing and therapy procedures 

(currently set at $10,000), and when 

the variety is released from quarantine 

it is delivered to the owner and is not 

maintained in the CCPP Foundation 

Blocks (see section E). 

E. Maintenance 

The Lindcove Foundation and Evaluation 

Block 

The newly introduced varieties that 

have been pathogen tested and found 

“clean” and released from state and 

federal quarantine are propagated at 

Rubidoux on suitable rootstocks for field 

planting in the Foundation and Evaluation 

Block. The CCPP Foundation and 

Evaluation Block is located at the University 

of California Lindcove Research 

and Extension Center near Exeter in the 

San Joaquin Valley of California. This is a 

field planting of about 20 acres and now 

contains over 1,200 trees and over 300 

different scion and rootstock varieties. 

The Foundation and Evaluation 

Block is planted on fumigated soil and 

has a wide planting distance between 

rows and trees to allow for better visual 

evaluation of each tree. Each tree of 

the Foundation and Evaluation Block 

is examined several times each year 

by CCPP and interested University 

and industry people for horticultural 

trueness-to-type, fruit quality, freedom 

from budsports and chimeras, spontaneous 

genetic disorders, and symptoms 

of disease. Until 2007, each tree was 

annually re-indexed biologically and by 

ELISA for tristeza and was tested up to 

three more times by ELISA during the 


annual budwood distributions. Any tree 

showing abnormal growth characteristics 

or which tests positive for disease is immediately 

removed from the block, and 

the soil is fumigated prior to planting of 

another tree. 

In 2006 and 2007, a significant number 

of trees in the Lindcove station tested 

positive for tristeza, and some of them 

were located in the CCPP Foundation 

and Evaluation Block. This epidemic was 

the result of increasing natural spread of 

the disease in the commercial orchards 

surrounding the Lindcove station. Therefore, 

after almost 50 years of budwood 

distribution from the outdoor field block, 

the CCPP began budwood distribution 

exclusively from the Protected Foundation 

Block. The outdoor block is now 

used only as a trueness-to-type Evaluation 

Block for trees propagated from the 

Protected Foundation Block. Testing for 

tristeza continues annually with ELISA, 

and tristeza-infected trees continue to 

be removed. For an overview of the 

budwood movement after quarantine 

release, see Figure 7. 

The Lindcove Protected 

Foundation Block 

When CTV-infected tree removal in 

the commercial citrus surrounding Lindcove 

ended in 1998, the CRB sponsored 

the construction of a 40,000 sq. ft. (~3,700 

m 2 ) protective screenhouse, completed 

in two phases between 1998 and 1999. 

In 2007, after positive tristeza findings 

Fig. 8. Panoramic view of the Citrus Clonal Protection Program Protected 

Foundation Blocks (PFB) and laboratory facilities at the Lindcove Research and 

Extension Center in Tulare County (A, figure was edited by Toan Khuong), the first 

screenhouse (40,000 sq, ft, ~3,700 m 2 ) constructed between 1998 and 1999 (B), 

the second screenhouse (30,000 sq. ft. ~2,800 m 2 ) completed in 2010 (C), the 

interior of the PFB with both container (D) and in-ground planted trees (E). 


Fig. 7. Schematic representation of citrus budwood movement through quarantine 

and distribution to the California industry via the Citrus Clonal Protection 

Program (CCPP). 

in the Foundation and Evaluation Block, 

the screened Protected Foundation 

Block became the primary source of 

budwood. In 2008, the CRB committed 

the necessary funds for the expansion 

of the protected block by 30,000 sq. ft. 

(~2,800 m 2 ). Construction was completed 

in 2010, and tree planting began in the 

spring of 2010.Today, the Protected 

Foundation Block contains 750 trees, 

representing approximately 400 varieties 

(Fig. 8). The CCPP maintains both 

potted and in-ground trees inside these 

structures for the varieties that traditionally 

have high budwood demand. 

F. Registration of trees and budwood 

availability 

Prior to the distribution of any budwood 

from Foundation Block trees, they 

must be registered as budwood source 

trees with the CDFA. Registration by 

CDFA requires that trees be tested for 

tristeza, viroids and psorosis. If these 

tests are all negative, the tree is then 

assigned a CDFA registration number 

which must accompany any budwood 

distributed from any foundation tree. In 

order to remain as registered budwood 

sources, the CCPP re-indexes the Protected 

Foundation Block trees annually 

for tristeza, every three years for citrus 

viroids, and every five years for psorosis. 

In 2010, regulations for a mandatory 

Citrus Nursery Stock Pest Cleanliness 

Program were filed as an emergency 

action, based on the authority conveyed 

in Food and Agricultural Code, 

Sections 6940-6945. This new program 

includes testing for additional diseases 

such as Huanglongbing (HLB). Most 

importantly, it also contains provisions 

to include exotic or emerging diseases 

as they become a threat to the budwood 

distribution scheme and to approve new, 

robust, and economic diagnostic technologies 

as they are developed. 

Only when the process of registering

source trees is completed can budwood 

from the CCPP Lindcove Foundation 

Blocks be distributed to the California 

nurserymen and growers. Limited 

quantities of budwood are available, 

and recipients normally use Foundation 

Block budwood to produce their own 

nursery- or grower-owned registered 

trees or nursery increase blocks, which 

are also regulated by CDFA. 

There is also provision for the distribution 

of limited amounts of “Early 

Release” budwood from containergrown 

trees of some selected newer 

varieties maintained in the protected 

screenhouse at Lindcove. “Early Release” 

variety trees have not fruited 

but have otherwise undergone all the 

required indexing and are registered 

with CDFA. Recipients of small lots of 

“Early Release” budwood understand 

that the fruiting characteristics of that 

particular budline have not yet been 

evaluated by CCPP. A waiver of liability 

for budwood that may not be horticulturally 

true-to-type or may contain budsports 

must be signed prior to receiving 

“Early Release” budwood. 

Budwood from the CCPP Protected 

Foundation Block is cut three times per 

year: January, June and September. The 

CCPP primarily serves the California 

citrus nurserymen and growers, but 

clients outside the state can request 

budwood. Budwood cut dates, order 

forms, prices, and other information 

is available at http://ccpp.ucr.edu/budwood/budwood.php. 

Letters are sent 

out prior to each cut and announce the 

specific date of the cut as well as a list 

of available varieties. 

Fig. 9. Schematic representation of Florida’s citrus budwood introduction 

program-Citrus Germplasm Introduction Program (CGIP). ELISA: enzyme-linked 

immunosorbent assay, CTV: Citrus tristeza virus, TLCSV: Tatter leaf citrange stunt 

virus, S. citri: Spiroplasma citri, X. fastidiosa: Xylella fastidiosa, PCR: polymerase 

chain reaction, rt: reverse transcription, CLBV: Citrus leaf blotch virus, CpsV: Citrus 

psorosis virus, sPAGE: sequential polyacrylamide gel electrophoresis, dsRNA: 

double stranded RNA, CG: Concave gum, CVV: Citrus variegated virus. 

G. Outreach 

The CCPP makes all the information 

related to budwood distribution, 

variety evaluation, citrus disease and 

management issues available to the 

public via the web www.ccpp.ucr.edu 

and publication in agricultural magazines 

(for recently distributed citrus 

varieties see Citrograph March/April 

2010 pages 20-26), peer-reviewed journals, 

and scientific conferences. Yearly 

Foundation-Evaluation Block inspections 

or “walk-throughs” are scheduled 

by the CCPP for the benefit of the citrus 

nursery personnel and interested growers. 

The CCPP also is present at many 

local and international agricultural 

shows with booths displaying the citrus 

varieties of its collection and distributing 

information as to the program and 

its objectives. 

For more information on CCPP visit: 

www.ccpp.ucr.edu or contact 

Georgios Vidalakis, vidalg@ucr.edu 

or John Bash, john.bash@ucr.edu 

Tel: 951 684 8580 

Department of Plant Pathology and 

Microbiology 

University of California 

Riverside, CA 92521 

U.S.A. 

Florida 

In 1975, the Florida Department 

of Agriculture and Consumer Services 

(FDACS) Bureau of Citrus Budwood 

Registration in Winter Haven began 

removing graft-transmissible pathogens 

from Florida-grown citrus using shoottip-grafting 

and heat therapy. However, 

there was no approved method of importation 

for new citrus varieties into 

Florida, which most likely contributed to 


Table 1. Comparative summary of the citrus quarantine programs in USA 

Variety Introduction Therapy Commercial Foundation Blocks 

under Quarantine Budwood Distribution Re-testing 

California 

Citrus Clonal Protection Program (CCPP) Yes Yes Yes Yes 

Florida 

Citrus Germplasm Introduction Program (CGIP) Yes Yes No N/A 

Citrus Nursery Stock Certification Program No Yes Yes Yes 

Arizona 

Certified Budwood Program No No Yes Yes 

Texas 

Texas A & M University-Kingsville 

Citrus Center Program No Yes Yes Yes 

Louisiana 

Louisiana State University No No No N/A 

Agricultural Center Citrus Research Station 

material from other programs 

Alabama 

Auburn University No No No N/A 

Alabama Agricultural Experiment Station 


Hawaii 

University of Hawaii No No No N/A 

Department of Plant and Environmental 


Protection Sciences 

N/A: not applicable 

the illegal introduction of citrus varieties 

into that state. In one budwood importation 

case, more than 210 acres or 95,000 

trees were found as grove plantings and 

nursery stock infected with viral diseases 

exotic to Florida. 

Aware of the risk associated with the 

introduction of out-of-state budwood, 

FDACS proposed the establishment of 

an indexing program to be conducted in 

quarantine greenhouses and laboratories 

where foreign and domestic citrus 

germplasm could be shoot-tip grafted, indexed, 

and released as healthy budwood. 

By 1976, a plant quarantine facility with 

two indexing greenhouses (760 sq ft ~70 

m 2 ) and adjoining laboratory space was 

constructed by the FDACS Bureau of 

Plant Pathology in Gainesville, Florida. 

Two more greenhouses were added in 

1980, and for the next five years, three 

employees worked part-time “cleaning-up” 

and indexing citrus budwood, 

maintaining a maximum of five citrus 

selections and releasing one healthy 

variety every other year. Recognizing 

the need to increase the capacity of the 

introduction program, additional greenhouse 

space (3,000 sq ft ~280 m 2 ) and an 

office/headhouse facility (560 sq ft ~50 

m 2 ) were constructed in 2000. Backup 


foundation facilities (screenhouse and 

office/headhouse) are scheduled to be 

built in the near future. 

Today, the Citrus Germplasm Introduction 

Program (CGIP) can handle 30 

foreign and domestic varieties, with up 

to 10 new imports each year, as well as 

numerous Florida-grown field-selections 

in various stages of therapy and indexing. 

The program currently consists of 

three full-time employees who are crosstrained 

in duties and responsibilities: 

one manager who directs the program, 

compiles reports, maintains records and 

reads citrus indicators, one biologist who 

performs shoot-tip grafting, conducts 

laboratory-based testing and transmission 

electron microscopy, and one greenhouse 

technician who is responsible 

for greenhouse maintenance, pesticide 

application, plant propagations and graft 

inoculations. Additional program direction 

and decision-making is provided by 

the FDACS Division of Plant Industry’s 

(DPI) Assistant Director. Funding for 

the program is primarily provided by 

the state of Florida while additional 

funds are provided by national programs 

(e.g. Citrus Health Response Program 

(CHRP) and industry research grants. 

New varieties for introduction into 

Florida are chosen from requests submitted 

by individuals, companies and 

researchers. All requests must be approved 

by a citrus advisory committee 

and the Director of DPI. Importation of 

foreign citrus budwood is restricted by 

the USDA and requires a non-transferrable 

departmental permit issued to the 

program manager of the introduction 

program. This is the second of the three 

permits that allow introduction of citrus 

germplasm in the USA. Once budwood 

is received, it undergoes therapy and 

indexing to produce plants with no 

detectable pathogens. The process of 

introduction requires 18 months to five 

or more years depending on budwood 

quality and vigor, and then approval 

for release from the Citrus Budwood 

Technical Advisory Committee, DPI 

Director, and USDA (Fig. 9). Between 

2003 and 2008, a total of 138 selections 

were released from the program. In addition, 

more than 250 field selections of 

the University of Florida (UF) breeding 

program were submitted to CGIP that 

were either infected with severe strains 

of CTV or exposed to citrus canker or 

Huanglongbing (citrus greening). 

For more information on the Citrus 

Germplasm Introduction Program in

Florida visit: http://fl-dpi.com/enpp/ 

germplasm/protocol.html or contact 

Lisa L. Williams, 

willial1@doacs.state.fl.us 

Tel: 352 372 3505 ext 498 

Citrus Germplasm Introduction 

Program 

FDACS DPI 

1911 SW 34th St. 

Gainesville, FL 32608 

U.S.A. 

Arizona, Texas, Louisiana, Alabama, 

and Hawaii 

The states of Arizona, Texas, Louisiana, 

Alabama and Hawaii do not have 

a Quarantine-Introduction program. 

Citrus budwood is distributed to these 

states from the CCPP, NCGRCD and/or 

the Florida Bureau of Citrus Budwood. 

In the case of Texas, testing and therapy 

protocols are employed for some local 

citrus selections. 

Authors’ affiliation information 

1 

Citrus Clonal Protection Program, 

Department of Plant Pathology and Microbiology, 

University of California, Riverside, 

CA 92521, USA, vidalg@ucr.edu 

2 

Texas A & M University-Kingsville, 

Citrus Center, Weslaco, TX 78596, USA, 

JDaGraca@ag.tamu.edu 

3 

Florida Department of Agriculture and 

Consumer Services. PO Box 147100, Gainesville, 

FL, dixonw@doacs.state.fl.us 

4 

Department of Plant Pathology and 

Crop Physiology, Louisiana State University 

Agricultural Center, 302 Life Science, 

Baton Rouge, LA 70803, USA, DFerrin@ 

agctr.lsu.edu 

5 

Florida Department of Consumer Services’, 

Bureau of Citrus Budwood Registration, 

3027 Lake Alfred Rd. (US 17), Winter 

Haven, FL 33881, USA, kesingm@doacs. 

state.fl.us & sieburp@doacs.state.fl.us 

6 

USDA-ARS National Clonal Germplasm 

Repository for Citrus & Dates, Riverside, 

CA 92507, USA., robert.krueger@ars. 

usda.gov & richard.lee@ars.usda.gov 

7 

Department of Plant and Environmental 

Protection Sciences, College of Tropical 

Agriculture and Human Resources, University 

of Hawaii, 3050 Maile Way, Honolulu, HI 

96822, USA, melzer@hawaii.edu 

8 

Alabama Agricultural Experiment 

Station, Auburn University, 411 North 

McGregor Ave., P.O. Box 8276, Mobile, AL 

36689, USA, olivejw@auburn.edu 

9 

Citrus Research Board, 323 W. Oak, 

P.O. Box 230, Visalia, CA 93279, marylou@ 

citrusresearch.org 

10 

Citrus Germplasm Introduction Program, 

Division of Plant Industry, 1911 SW 

34th St. Gainesville, FL, 32608, USA, willial1@doacs.state.fl.us 

11 

University of Arizona, Yuma Agriculture 

Center, 6425 W. 8th Street, Yuma, AZ 

85364, USA, gwright@ag.arizona.edu 

Selected literature 

Bash J. 1997. The California Citrus 

Clonal Protection Program. Pages 323-327 

in: Proceedings of the 5th ISCN International 

Congress. 

Calavan C.E., Mather S.M., and McEachern 

E.H. 1978. Registration, certification, and 

indexing of citrus trees. In Reuther W., Calavan 

C. E., and Carman G. E. (eds.). The citrus 

industry Vol. IV. Crop protection. Chapter 

3, pages 185-222. University of California, 

Division of Agricultural Sciences. 

Calavan EC, CN Roistacher, and EM 

Nauer 1972. Thermotherapy of citrus for 

inactivation of certain viruses. Plant Disease 

Rep 56:976–980. 

Frison, E. A., and Taber, M. M. (eds.). 

1991. FAO/IBPR Technical guidelines for the 

safe movement of citrus germplasm. FAO, 

Rome. 50 pages. 

Gumpf D. J., Bash J., Greer G., Diaz J., 

Serna R. and J. Semancik. 1996. The California 

Citrus Clonal Protection Program. Proc. 

Int. Soc. Citriculture, 445-447. 

Gumpf, D. J. 1999. Citrus quarantine, 

California. pp. 151-156. In: R. P. Kahn and S. B. 

Mathur (eds.) Plant pest and pathogen exclusion: 

containment facilities and safeguards. 

American Phytopathological Society Press. 

Hiltabrand W.F. 1959. Certification program 

for maintenance of virus-free propagation 

sources of citrus in California. In: 

Wallace J. M. (ed.) Citrus virus diseases. pp. 

229-31. Univ. Calif. Div. Agr. Sci., Berkeley. 

Kahn T.L., Krueger R.R., Gumpf D.J., 

Roose M.L., Arpaia M.L., Batkin T.A., 

Bash J.A., Bier O.J., Clegg M.T., Cockerham 

S.T., Coggins C.W. Jr., Durling D., Elliott G., 

Mauk P.A., McGuire P.E., Orman C., Qualset 

C.O., Roberts P.A., Soost R.K., Turco J., Van 

Gundy S.G., and Zuckerman B. 2001. Citrus 

Genetic Resources in California. Analysis 

and Recommendations for Long-Term 

Conservation. Report of the Citrus Genetic 

Resources Assessment Task Force. Report 

No. 22. Genetic Resources Conservation Program. 

Division of Agriculture and Natural 

Resources. University of California. http:// 

www.grcp.ucdavis.edu/publications/doc22/ 

full.pdf 

Lee, R. F. 2003. Certification programs 

for citrus. Pgs 291-305. In: Management of 

Fruits and Vegetable Diseases. Diagnosis 

and Management. Vol I. (Naqvi, S. A. M. 

H., Ed.) Kluwer Academic Publishers, The 

Netherlands. 

Lee, R. F., P. Lehmann and L. Navarro. 

1999. Nursery practices, budwood and 

rootstock certification programs. In: Citrus 

Health Guide. L. W. Timmer and L. Duncan, 

Eds. APS Press, Minn. Pgs 35-46. 

Nauer E. M., E. C. Calavan, C. N. Roistacher, 

R. L. Blue and J. H. Goodale. 1967. 

The Citrus Variety Improvement Program 

in California. California Citrograph, 52: 133, 

142, 144, 146, 148, 151, 152. 

Navarro, L., Roistacher, C. N., Murashige, 

T. 1975. Improvement of shoot tip grafting in 

vitro for virus-free citrus. J. Am. Soc. Hortic. 

Sci. 160:471-479. 

Reuther W. 1959. A program for establishing 

and maintaining virus-free citrus 

stock. In: Wallace J. M. (ed.) Citrus virus 

diseases. pp. 215-17. Univ. Calif. Div. Agr. 

Sci., Berkeley. 

Reuther W. 1981. The Citrus Clonal Protection 

Program. Calif. Agriculture. 35: 30-32. 

Reuther W., Calavan E. C., Nauer E. M. 

and Roistacher C. N. 1972. The California 

citrus variety improvement program after 

twelve years. pp. 271-278 In: Proc. 5th Conf. 

Int. Organ. Citrus Virologists. IOCV, Riverside. 

Roistacher, C. N. 1991. Graft transmissible 

diseases of citrus. Handbook for detection 

and diagnosis. FAO, Rome 1990. 

Rucks P.. 1994. Quality tree program 

for Florida citrus. Proc. Fla. State Hort. Soc. 

107:4-8. 

Skaria, M., C. J. Kahlke, N. Solis-Gracia 

and R. Prewett. 1997. Virus-free citrus budwood 

production and tristeza management 

program in Texas through industry partnership. 

Subtrop. Plant Sci. 49: 1-7. 

Wallace J.M. and Drake R.J. 1959. An 

indexing program to avoid viruses in citrus 

introduced into the United States. In: Wallace 

J. M. (ed.) Citrus virus diseases. pp. 209-214. 

Univ. Calif. Div. Agr. Sci., Berkeley. 

Wallace, J. M. 1978. Virus and viruslike 

diseases. In Reuther W., Calavan C. E., and 

Carman G. E. (eds.). The citrus industry 

Vol. IV. Crop protection. Chapter 2, pages 

67-184. University of California, Division of 

Agricultural Sciences. l 

Jul 9 

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