Scion/Rootstock Incompatibility as the Cause of Tree Decline in Fukumoto Navel Craig Kallsen and Neil O'Connell
Fukumoto navel is an early-maturing navel with highly marketable fruit characteristics. While the fruit is in demand, many growers have had problems with tree decline. Graft union incompatibility appears to be the major reason for decline, but why some orchards are severely affected by decline and others suffer little damage remains a question.
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Petroleum Oils as Navel Orange and Tangelo Fruit Thinning Agents Craig Kallsen
Based on the apparent ability of petroleum oils to affect fruit bearing, the objective of this research was to determine if concentrated sprays of narrow-range oil could be used as fruit thinning agents for navel oranges and tangelos in the San Joaquin Valley of California.
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Registration of 2,4-D for Fruit Size and Yield Increase of Mandarins and Mandarin Hybrids in California C. Thomas Chao
The overall goal of this project is to have permanent registration of 2,4-D for fruit size increase of mandarins and mandarin hybrids in California. 2005-2006 was the third and last year of the project.
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Improving Efficacy of GA3 to Increase Fruit Set and Yield of Clementine Mandarins in California C. Thomas Chao and Carol J. Lovatt
The goal of this research is to identify the proper dose and best timing of GA3 application for increasing fruit set and packout of commercially valuable large size fruit of Nules Clementine mandarin and to demonstrate the negative effects resulting from use of high rates of GA3 or from numerous applications of lower rates of GA3 on yield and fruit size in the current and following years.
( 162 kb)

Production and Management Strategies for New Mandarins in California C. Thomas Chao
Understanding the process of compatibility and cross-pollination will help growers manage the issue of seediness in mandarin production. There were two objectives for 2005-2006: (1) Study the compability and seediness among new mandarins and existing citrus cultivars, and (2) Study strategies to enhance fruit set, yield, and fruit quality of new mandarins through pollination.
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Using Regulated Deficit Irrigation to Optimize Fruit Size in Late Harvest Navels David A. Goldhamer
This paper summarizes our four-year experiment on regulated deficit irrigation (RDI) with late harvest (Lane Late) citrus. Grower profits with late harvest navels can be significantly reduced due to both excessively large fruit and granulation. We evaluated four RDI regimes in addition to a fully irrigated Control in a commercial orchard in eastern Tulare County.
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Irrigation Stress and Early-Navel Fruit Maturity Craig Kallsen and Blake Sanden
Previous experiments conducted in Florida with sweet orange and in Japan with Satsuma mandarins demonstrated that water stress increased fruit soluble solids... The objective of this experiment was to measure the effects of water stress on yield and fruit quality factors, such as fruit size, color, juiciness, and sweetness of early-maturing Beck navel in the southern San Joaquin Valley of California.
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Etiology and Management of Rind Breakdown of Mandarins J. E. Adaskaveg
Preharvest rind breakdown of mandarins has caused severe crop losses in many citrus growing areas of California... In four years of study in Butte County and in three years in Fresno County, fungicide treatments only slightly and inconsistently reduced the incidence of disease. Thus our data indicate that mandarin rind breakdown is a physiological, abiotic disorder of fruit rather than a pathological problem caused by fungi or other organisms.
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Production Trial of Newly Introduced Citrus Cultivars in California C. Thomas Chao
The overall objective of this project was to establish a long-term production evaluation system for all newly introduced citrus cultivars in California. The specific objectives at this stage were to evaluate fruit quality and production potential of new citrus cultivars at trials that have already been established.
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Citrus Rootstock Breeding and Evaluation Mikeal L. Roose
Citrus rootstock breeding is a very long-term project aimed at providing the California citrus industry with a diversity of new rootstocks that improve productivity and profitability. New hybrid rootstocks and those imported from elsewhere are compared with standard rootstocks for yield, tree size, disease resistance, fruit quality, soil adaptation, compatibility with important scion varieties and other traits.
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Citrus Variety Evaluation for Trueness-to-Type and Commercial Potential Tracy L. Kahn
Our project continues to provide the industry with preliminary data on the characteristics of new citrus varieties in California and evaluate trueness-to-type of varieties distributed by the Citrus Clonal Protection Program (CCPP). We also direct the citrus demonstration blocks and the Citrus Variety Collection as resources for evaluations and as demonstration material to allow growers to view trees and fruit of new and commercial citrus varieties.
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Breeding of New Citrus Scion Varieties Mikeal L. Roose
The UC Riverside citrus scion breeding program is a long-term project, funded by the CRB since 1994, that is focused on developing new mandarin, orange, lemon and grapefruit cultivars suitable for California. Identification of the correct parents to hybridize remains a high priority which is being addressed by ongoing work with DNA markers.
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Harvest and Evaluation of Strain Trials at Lindcove Research and Extension Center Mary Lu Arpaia
This project provides support for the continued maintenance of two trials at the UC Lindcove Research and Extension Center in Exeter, CA. There is one trial evaluating the potential of 17 navel strains and another trial evaluating the Delta, Midknight, and Olinda Valencia strains on two rootstocks. The data collected includes yield, packout, color and fruit quality.
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Evaluation of Lemon Selections for the Desert Glenn C. Wright and Tracy L. Kahn
To maintain and increase its market share, the California lemon industry must develop high quality lemon varieties that produce satisfactory income for the grower, meet the needs of the marketplace, and are adaptable to the varied California climate. This project is designed to assess several lemon selections under desert conditions, in a 10-year trial.
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Genetic Engineering of Citrus Henry J. Fisk and Abhaya M. Dandekar
The main focus of this project has been on the development of genetic transformation methods for citrus rootstock and scion cultivars important to the California industry. Establishment of this technology would represent a significant advancement towards efforts to better understand and improve these species using methods based in conventional breeding, biotechnology, or a combination of the two.
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Development of Citrus Culivars with Reduced Juvenility Henry J. Fisk
The primary focus of this project has been to learn more about the flowering response in citrus in attempt to reduce juvenility. A key hypothesis that formed the basis of this work was that transgenic citrus species over-expressing a genetic regulator of flowering response from Arabidopsis thaliana or its functional equivalent from Washington navel orange would have reduced juvenility characteristics with respect to flowering.
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Physiological and Biochemical Determinants of Sugar and Acid Content in Citrus Fruits and Citrus Fruit Proteomics Eduardo Blumwald
The sugar content and acidity of the juice cells are key determinants of citrus fruit quality. Total acid and sugar contents in the fruit are determined by the relative influence of two processes: sugar and acid transport into the fruit, and sugar and acid metabolism. The understanding of the mechanisms regulating these two processes is vital to the development of practices that would assure optimal sugar concentrations and acidity in the fruit at harvest and the development of postharvest pra
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Improving Peel Quality of California Citrus Fruit Abhaya M. Dandekar
Peel disorders lower fruit quality and thus returns to growers and producers. Peel quality results from specific gene expression in peel tissues; disorders are caused by lack of or aberrant expression of specific genes. Our study has two objectives: survey gene expression patterns in peel that determine citrus fruit quality, and identify and validate genes associated with fruit quality and peel-related disorders.
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Evaluating and Validating Seedlessness Strategies for Citrus Abhaya M. Dandekar
Several genetic strategies reduce or eliminate seeds in fruit. We are evaluating the ability of ovule-specific auxin regulation to induce parthenocarpy. Parthenocarpy is fruit formation in the absence of fertilization. It occurs naturally in some plants and results in seedless fruits. We are testing this strategy in tomato and then citrus by manipulating auxin synthesis or responsiveness in ovules of these plants with tissue-specific promoters.
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EST Libraries and Bioinformatics for California Citrus Timothy J. Close and Mikeal L. Roose
This project produces fundamental resources and information in the area of "Genomics" that facilitate other research and practical applications. The information is about the genes, proteins, and metabolic pathways of citrus. Research applications include identification of genes that underlay retention of flavor during fruit storage, predisposition of sour orange to quick decline, and development of transgenic strategies to investigate gene-trait relationships and develop new varieties.
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Genetic Maps of Sweet Orange and Trifoliate Orange Mikeal L. Roose and Timothy J. Close
Genetic linkage maps are valuable for citrus breeding because they help breeders locate and select for genes that control valuable traits. They are also an essential component in genomics research. In this project, which involves collaboration between the Roose and Close labs at UCR and the Gmitter and Chaparro labs at the University of Florida, the main objective is to develop very detailed reference maps of sweet orange and trifoliate orange.
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Biology and Management of Septoria Spot of Citrus J. E. Adaskaveg
Because recent outbreaks of Septoria spot have caused trade restrictions for California oranges in the Korean market, epidemiological field studies have been initiated to identify specific environmental conditions conducive for disease development and to determine when infections occur and the duration of the latent period for symptoms to develop. Additionally, new rapid detection methods for correctly diagnosing the disease are being developed and management practices are being re-assessed.
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Etiology, Epidemiology, and Management of Hyphoderma Gummosis J. E. Adaskaveg
This new disease of lemon represents a serious threat to the industry. Once branches are invaded by the pathogen, dieback, tree decline and eventual tree death occurs rapidly... Historically, most branch and trunk invading organisms are often difficult to manage, and with little or no prior information specifically available about this disease the problem will be challenging. Thus, information needs to be developed on the biology and ecology of the pathogen as well as on the epidemiology and ma
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Development and Management of a Genomics Database for Microarray-based Detection Systems for Citrus Pathogens Edwin Civerolo
The overall goal is to develop a comprehensive bioinformatics data warehouse of citrus pathogens and pests to aid in the disease early diagnosis and pathogen detection. The specific objective was to maintain and update the genomic information as well as conduct comparative analyses for the development of microarray-based pathogen detection systems. The citrus pathogens targeted for this project were Xylella fastidiosa, citrus tristeza virus, and huanglongbing.
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Evaluation of Transgenic Carrizo for Rootstock and Scion Delivery of CTV Silencing Bryce W. Falk
This project builds from our previous project on CTV RNA silencing. There we showed that we could construct artificial resistance transgenes for Citrus tristeza virus (CTV) and these were effective for conferring resistance in transgenic Nicotiana benthamiana plants when the plants were inoculated using a heterologous virus that contained CTV sequences. While we were evaluating the transgenic N. benthamiana plants, we also developed transgenic Carrizo plants containing the same transgenes. Ou
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San Joaquin Valley Insecticide Efficacy Trials for Citrus Pests Beth Grafton-Cardwell
The purpose of this project is to screen new insecticides for efficacy against pests including scales, mites, katydids and ants. Information derived from this project is used to update the UC IPM Pest Management Guidelines, produce Arthropod Management Test articles, and support new insecticide registrations.
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Long-Term Effects of Chloronicotinyls on Citrus IPM Beth Grafton-Cardwell
The question that we asked with this set of experiments is whether or not the glassy-winged sharpshooter (GWSS) treatments of Assail or Admire help or hinder control of other pests of citrus. Secondly, we wanted to know if increasing the rate of Assail would be of benefit in controlling those other pests.
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Monitoring for Pesticide Resistance in California Red Scale Beth Grafton-Cardwell
The purpose of our current project is to determine if organophosphate insecticide-resistant populations of California red scale have lost any of their resistance to organophosphates (Lorsban or Supracide)and to see if any populations have developed resistance to Esteem.
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Evaluation of the Effects of Micromite (diflubenzuron) on Forktailed Katydids Beth Grafton-Cardwell
Micromite (diflubenzuron, Dimilin) is a recently registered insect growth regulator that appears to have good activity on katydid nymphs and is relatively safe for natural enemies. During 2004-2006 we conducted a detailed greenhouse study to determine the effect of Micromite on katydid eggs, nymphs, and adults.
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Infrastructure for Armored Scale Research Robert F. Luck
This is a continuing project with the purpose of supporting all aspects of California red scale (CRS) pest management strategies. CRS remains a primary pest of citrus in the San Joaquin Valley. As new pests enter California citrus, red scale research must develop efficacious control tactics that can integrate into new pest management practices.
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Integrating Chloronicotinyl Pesticides with Red Scale Biological Control Joseph G. Morse, Robert F. Luck, and Beth Grafton-Cardwell
The mission of this project was to investigate the impact of Admire and Assail on the natural enemies suppressing California red scale (CRS) in the San Joaquin Valley (SJV), including Aphytis melinus. This project interfaced with Grafton-Cardwell's CRB project, "Long-term effects of chloronicotinyls on citrus IPM."
( 360 kb)

Survey for Soft Scale Parasitoids in Interior Southern California Joseph G. Morse and Robert F. Luck
This project sought to identify the complex of parasitoids attacking soft scales year-round in southern California with the intent of improving biological control of black scale in southern California and citricola scale in the San Joaquin Valley.
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Management of Citrus Thrips Joseph G. Morse
Citrus thrips populations vary from year to year and require that growers and pest control advisors monitor carefully and apply treatments on an as-needed basis. This research project attempts to optimize cultural, biological, and/or chemical controls, which might be used to manage economic citrus thrips populations.
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Management of Bean Thrips Joseph G. Morse
This insect is not considered an economic pest on citrus in California but it became a problem for California growers shipping navel oranges to Australia during the 1996-97 season... We are winding down this project generally as proposed but with some changes in objectives based on feedback from citrus growers, results from field trials, and feedback from USDA-APHIS.
( 139 kb)

Seasonal Phenology of Leafminer Peggy A. Mauk and Gary Bender
The objectives of this study were to determine the host plants used by citrus leafminer (CLM) throughout the year in the Southern California (Escondido) area, to determine seasonal phenology, to determine the periods of moth flight activity in Southern California, and to determine the species of parasites attacking CLM on various host plants throughout the year in the Southern California area.
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Texas Mite and Yuma Spider Mite Studies David Haviland
Texas citrus mite and Yuma spider mite are new pests of citrus in the lower San Joaquin Valley. Both of these pests have been long-time residents in southern citrus production areas of California but are behaving differently in the San Joaquin Valley. We began work in 2006 to gain an understanding of the basic biology of Texas citrus mite and Yuma spider mite in citrus in the SJV including seasonal fluctuations in mite density, their location in the trees, and the effects on the crop.
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Improvement of Citrus Peelminer Pheromone Lures Jocelyn G. Millar
Several years ago, we identified what appeared to be the main component of the pheromone of the citrus peelminer. However, in numerous trials conducted over several years in a variety of crops, the pheromone has not worked well enough and/or consistently enough to be incorporated into routine IPM programs. We suspect that the problem is due to subtleties in the chemistry of the pheromone.
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Foreign Exploration and Rearing Citrus Peelminer/Parasitoids at UCR Quarantine Facility Joseph Morse, Robert Luck, David Headrick, and Beth Grafton-Cardwell
Citrus peelminer (CPM) has become an economic problem in both the San Joaquin and Coachella Valleys... We need to determine whether to import parasitoids from Mexico for release in the SJV and the Coachella Valley. We also need to determine whether inoculative or augmentation releases of native parasitoids should be pursued as a CPM suppression tactic.
( 299 kb)

Survey of California Citrus and Other Plants for Brevipalpus Mites That Could Potentially Vector Citrus Leprosis Virus Beth Grafton-Cardwell, Carl Childers, Jose Carlos Rodriguez, Joseph Morse
Citrus leprosis disease is present in a number of South American countries and was recently found in Mexico. Leprosis virus is transmitted by Brevipalpus sp. mites. While we do not have the disease in California, we do have at least two species of Brevipalpus mites in citrus, and there may be additional species of Brevipalpus mites in California of which we are not yet aware.
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Diaprepes Phenology and Insecticidal Control in San Diego County Kris Godfrey and Gary Bender
Diaprepes root weevil is a serious threat to agricultural and nursery production in California. Research on phenology and insecticidal control began in July 2006 in San Diego County after infestations were found in Orange, Los Angeles, and San Diego counties in late 2005 and early 2006. Initial efforts of this research focused on investigating the phenology of the weevil to determine the proper timing of treatment efforts. This report summarizies research activities from July 2006 through Oct
( 157 kb)

Field Management Plan and Biocontrol Rearing System for Citrus Peelminer David H. Headrick and Beth Grafton-Cardwell
This project has four objectives: (1) Development of a pheromone-based monitoring system, (2) Development of a degree-day model, (3) Biological control introduction and augmentation, and (4) Development of arcIMS as a tool to map peelminer infestations and evaluate neighboring crop effects. This report includes information from travel to Hermosillo, Mexico, in November 2006.
( 447 kb)

Evaluation of New Postharvest Treatments to Reduce Postharvest Decays and Improve Fruit Quality in Citrus Packinghouse Operations J. E. Adaskaveg
New fungicides are being developed for the management of postharvest decays of citrus... Overall, our research objectives include new concepts for managing postharvest decays and reducing the development of resistance in populations of postharvest pathogens of citrus using integraged approaches.
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New Methods to Control Postharvest Decays of Citrus Joseph L. Smilanick
The purpose of this project is to evaluate new methods to extend the postharvest life of fresh citrus fruit. Currently, our research is organized in pursuit of three objectives: (1) Optimize effectiveness of packinghouse treatments to minimize decay losses, (2) Evaluate populations of the green mold pathogen Penicillium digitatum, particularly regarding their sensitivity to fungicides, and (3) Characterize molecular aspects of fungicide resistance among isolates of P. digitatum.
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Survey of Sensing Methods for Detection of Freeze Damage in Oranges James F. Thompson, David Slaughter, and Michael McCarthy
The goal of this project is to develop and test field methods for using an ethanol sensor and magnetic resonance to measure whether a sample of oranges contains a threshold level of freeze-damaged fruit.
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Relationship Between SSC/TA Ratio and Acceptability of Navel Orange Mary Lu Arpaia and David Obenland
The anticipated outcome of this project will be a database that will assist the California citrus industry in deciding whether the current legal minimum maturity is adequate and is supplying consumers with fruit of acceptable quality or whether the legal minimum maturity needs to be modified.
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Robotic Mechanical Harvester for Fresh Market Citrus Bret Wallach
2005-2006 was the third year of collaboration between Vision Robotics Corporation and the CRB on the robotic mechanical harvester. The harvester is a multi-year project which will ultimately require significant private funding. This is a two robot system, the scout and the picker.
( 180 kb)

Support for a Dedicated Facility for Sensory Evaluation at the UC Kearney Research and Extension Center M. L. Arpaia and J. E. Adaskaveg
Sensory analysis is a crucial part of the postharvest research program in general and plays a pivotal role in our citrus research efforts. Sensory analysis focuses on research developments for an improved consumer product. The objective of this project is to gather funding from various sources in order to construct a dedicated facility for sensory evaluation at the UC Kearney Ag Center in Parlier.
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Efficacy of Ozone Combination Treatment to Control Bean Thrips in Navel Oranges James G. Leesch
This project continued research on the use of ozone combined with carbon dioxide and vacuum to control bean thrips in navel oranges, including investigating wax type and cultivar to mitigate any phytotoxic damage to navel oranges.
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2005-2006 Assessment Rate, Income and Expenses
An assessment rate of 28 mills (2.80 cents) per standard field box (55 lb. equivalent) was recommended by the Citrus Research Board to the Department of Food and Agriculture for the State of California in order to provide the funds to support 2005-2006 research projects...
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Citrus Clonal Protection Program Geogios Vidalakis
The California Citrus Clonal Protection Program (CCPP) is a part of the University of California/Riverside Department of Plant Pathology. The CCPP is a cooperative program with the California Department of Food and Agriculture, the U.S. Department of Agriculture Animal and Plant Health Inspection Service (USDA-APHIS), and the citrus growers of the state of California represented by the Citrus Research Board.
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California Citrus Quality Council (CCQC) Hugh W. Ewart, President
As specifically provided for in the California Citrus Improvement Program marketing order, this ongoing Quality Assurance Program is conducted by the California Citrus Quality Council (CCQC) under an operating agreement with the California Citrus Research Board. CCQC's mission is to represent the California citrus industry in response to problems and issues which arise in state, national, or international arenas and which affect the industry generally in areas of quarantine matters, technical a
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