002-01M - Rootstock Interactions with Disturbed Soil Profiles in Flatwoods Citrus
002-03M - Enhancing Citrus Cropping Through Controlling Flowering and Improving Fruit Size Through Thinning
002-07M - Ecolyst Application Timing, Juice Brix, and Profitability of Oranges
002-13M - Implementation of the Decision Information System for Florida Citrus
005-04M - Tree Pruning Studies to Improve the Production and Harvesting of Florida Oranges
981-02M - Development of a Precision Agriculture System to Manage Florida Citrus
981-10M - Phosphorus/Potassium Soil Test Calibration and Effects on Fresh Citrus Fruit Quality

001-11M - Sprayer Air Energy Demand for Satisfactory Spray Coverage
001-15M - A Computer Decision-Aid To Evaluate Tree Replacement Strategies
991-40M - Detecting and Managing Water Stress in Flatwoods Citrus

003-01P - Diaprepes Damage and Interactions with Phytophthora
003-02P - Investigations into an Unknown Flaky Bark Disease on Grapefruit
003-04P - Studies to Determine the Cause and Develop Strategies to Control Citrus Blight
003-11P - Evaluation of Exotic Pathogen Threats to Florida
928-74P - Development of Methods to Manage Citrus Tristeza Virus
971-43P - Development of Detection Methods for Citrus Psorosis Virus and Use of the Virus as a Vector to Express Foreign Genes in Citrus
991-50P - Optimization of PCR Viroid Detection in Budwood Source Trees

981-29P - Research in Support of Eradication and Control of Citrus Canker
991-36P - Improving Performance of Fungicides for Control of Postbloom Fruit Drop, Greasy Spot and Alternaria Brown Spot
991-37P - Reducing Postbloom Fruit Drop Through Use of Plant Growth Regulators to Concentrate Bloom

002-06E - Residual Efficacy of Micromite on Diaprepes abbreviatus and Impact on Egg Parasitoids
002-15E - A Hydrophilic Particle Film for Control of Diaprepes abbreviatus and Other Citrus Pests
003-09E - Integrated Mite and Greasy Spot Control on Florida Citrus
942-18E - Biological and Chemical Controls for Citrus Root Weevil Larvae and Adults: Long-Term Control in Large Field Plots
971-14E - Mortality and Suppression of Egg Laying of Diaprepes abbreviatus
971-21E - Classical Biological Control of Citrus Psylla and Pink Mealybug
981-50E - Classical Biological Control of the Brown Citrus Aphid

Completed Projects
002-03E - Evaluating Biological Control Potential of Native Florida Nematodes Against Citrus Root Weevil (Diaprepes)
981-42E - Classical Biological Control of Diaprepes abbreviatus
991-52E - Field Tests of Alternative Candidates for Malathion and Efficacy Test for Diazinon in Mediterranean Fruit Fly Eradication and Caribbean Fruit Fly Protocol Programs

001-01I - A Scion and Rootstock Database for Information Management and Developing Recommendations for Growers
001-03I - Establishment of a Core Citrus Transformation Lab to Support the Genetic Improvement of Citrus
003-02I - Transfer and Testing of Potential Canker Resistance Genes to Florida Citrus
928-27I - Development and Evaluation of Improved Citrus Rootstocks
942-27I - Utilization of Gene-Mapping and Marker-Assisted Selection for Citrus Variety Improvement
981-30I - Field Evaluation of Promising USDA Rootstock Selections
991-98I - New Scion Variety Development for Florida Citrus Growers

Completed Projects
999-21O - Development of a Central Internet Resource for Citrus Information Worldwide

INTRODUCTION

Presented in this Ninth Annual Report is information about research conducted during Fiscal Year 2000-2001 supported by the Florida Citrus Production Research Advisory Council operating under the Florida Citrus Production Research Funding Order. This research support program was established under the Florida Marketing Act which enables Florida citrus growers to tax themselves for the purpose of providing funding to support needed research. Growers approved this marketing order by referendum in 1991 and the Council began its work in 1992.

Balance Forward 7-1-2000                         $1,466,970.22

Collections 7-1-2000 thru 6-30-2001            1,918,420.82

Refunds                                                                3,593.19

Research Projects                                         $1,172,437.00

Administrative Cost                                             44,485.80

Available for 2001-2002                             $2,172,061.43

December 31, 2001

Dear Florida Citrus Grower:

Looking over the past year, there has been major turmoil in the world, in our country and in the Florida citrus industry. Our troubles seem small in comparison to the overall scheme of things and, tough as it may seem, if we remain clever and diligent, the industry will weather the storm. The Florida Citrus Production Research Advisory Council (FCPRAC) has completed its ninth year under the grower-approved Florida Citrus Production Research Funding Order. The assessment to raise funds for citrus production research remains at ¾ of a cent per box for FY 2001-2002. The Council is striving towards coordinating research efforts statewide. Thus, eliminating duplication of work while encouraging cooperation. Some projects are long-term and broad in scope while many focus on short-term problems. More projects are forthcoming which will consolidate research agencies and pool research efforts. Administrative costs were 3.6% this year, due to the support of UF-IFAS CREC for office space and clerical support. Further savings are provided by UF-IFAS and USDA-ARS because they have waived normal overhead costs on all our projects.

Collections for FY 2000-2001 totaled $1,918,421.

Funding for research projects was $1,172,437.

Funding was provided for 38 projects selected from 44 proposals.

10 Plant Pathology

10 Entomology

8 Plant Improvement/Other

Over the past nine years, FCPRAC has directed $10,753,000 in funding on 346 new and continued Florida citrus production research projects. Your funds have enhanced the citrus research effort, much of which would have been left undone without this program.

A thank you goes to your Council members (listed previously) for their many volunteer hours away from work to make this program a success. I wish to express regret at the passing of Jim Simpson, who was past chairman of the council for four years. His quiet wisdom will be sorely missed!

This is my final year as chairman of your Box Tax Committee. As we continue to strive to maintain world-class citrus research in Florida, communicate your needs to the Council members. Statewide coordination of research is vital to get the most out of our funding dollars. Great strides have been made in this area and hopefully these efforts continue into the future. Thank you for your support and God bless America.

Andrew B. Pike

FCPRAC Chairman

^Z  Smaller numbers in parentheses are numbers of projects (new and continued), larger numbers are funding in dollars.

The Council views the monies invested through this program to be contributed by growers to enhance the existing research effort. In order to assure growers that their tax monies are in fact enhancing programs, the Council monitors overall citrus production research expenditures in relation to our funding. This section provides a summary of information received from IFAS and USDA-ARS regarding their research expenditures. The Council has not verified this information, and because we have not established firm definitions of each aspect of the research, we may see some adjustments in the future. Most of this information has not been presented in this form before. The Council can only provide this information because of the candid disclosures of the research institutions. We appreciate their openness and cooperation.

Progress Report for FY 00-01, Year 1 of 3.

Abstract

Rootstock selection in flatwoods Florida citrus groves is compromised to some extent by the natural variation among soil series, and the variation introduced by the bedding process required in these regions. The physical and chemical changes caused by bedding are largely unstudied. Nevertheless, they are a key element in tree performance because the surface of the natural soil and the overburden added from bedding are where most tree roots are located. We propose to characterize the natural and disturbed profiles of several representative soils planted with citrus, and several sites in which bedding rendered the soil unsuitable for commercial rootstocks, or where the rootsystem was able to overcome adverse conditions by expanding into more favorable parts of the profile.

Objectives

Summary of Accomplishments

A project manager was hired. The first phase of locating Indian River grove sites of poorly performing citrus trees on Swingle citrumelo, Carrizo citrange, Cleopatra mandarin, and Smooth Flat Seville rootstocks has been completed. These sites were matched with nearby locations, generally within the same block, of trees performing well. Samples have been taken from 20 such sites to confirm the Wabasso, Riviera, Winder, Chobee, and Pineda soils and characterize the specific locations. Tree sizes were measured, and tree condition described. Preliminary data to compare EM38 and Veris electrical conductivity measurements have been conducted; on Pineda soil, the correlation was excellent suggesting that both machines provide similar site information. Trees on 7 rootstocks planted in 5 soil types were measured for the second year, and two water table wells were installed in each site.

FCPRAC Grants $ 30,000
Agency Contribution $ 35,000
Other Grants $ 48,000

Total $113,000

Investigators: L. Gene Albrigo, IFAS - UF - CREC;Ed Stover,IFAS - UF - IRREC

Progress Report for FY 00-01, Year 1 of 2.

Excessive flowering compromises production of some Florida citrus varieties. GA applied during floral initiation reduces flowering, increases leafy bloom, alters bloom timing, and often increases total crop. Initial studies focused on Ambersweet and Navel, but other varieties may benefit from control of flowering. Time of GA application appears to influence tree response. We are studying the relationship between variety, environmental conditions before application, time of GA application, and tree response. GA was applied at mid Dec., early Jan., and late Jan. timings to Valencia, Ambersweet, and Late Navel and at the middle timing, three rates of GA were compared. Bloom was affected in all varieties, but only Ambersweet showed increased cropping. Cumulative effects of different thinning strategies were compared on Murcott, Sunburst and Flame. After one year, more large sized fruit were produced on NAA-thinned Sunburst and one of two Murcott blocks. Complete data on fruit number and yield per tree and fruit size distribution will be assessed again this year.

Summary of Accomplishments

In the Ridge, GA applied to Ambersweet on Dec. 30, 1999 or Jan. 20, 2000 increased yields by 30% with no significant increase from the Jan. 11th timing. In the Indian River area, GA applications influenced timing of flowering in all varieties. Late Jan. or early Feb. 2000, GA reduced bloom duration in Ambersweet and Late Navel. Only Ambersweet displayed an overall reduction in flowering from GA applications in 1999-2000. Only Ambersweet displayed a significant influence on cropping following GA treatment, with early Jan. treatments increasing cropping >50%. Initial results suggest that GA at 15 g/acre is as effective as 20 g/acre. Cumulative effects of different thinning strategies were compared on Murcott, Sunburst, and Flame. In the first year, more large sized fruit were produced on NAA-thinned Sunburst and one of two Murcott blocks. All experiments were established again this year. Flowering data were collected in the spring and complete data on fruit number and yield per tree and fruit size distribution will be assessed at harvest.

FCPRAC Grants $ 34,000
Agency Contributions $ 75,000
Grower Contributions-Time $ 5,000
Other Grants $ 0

Total $114,000

Thirty percent of 1 faculty and 25 percent of 1 faculty were applied to this project. Other infrastructure support was supplied at two locations of the University of Florida.

Investigator: Fred Davies, UF - Gainesville

Progress report for FY 00-01, Year 1 of 2.

Abstract

Ecolyst [diethyl -2-4-(4 methylbenzyloxy) ethyamine hydrochloride] is a recently developed plant growth regulator (PGR) that has been reported to increase juice Brix of Valencia oranges during preliminary experiments. Ecolyst has been applied during bloom; however, little is known about when and at what tree developmental stage Ecolyst should be applied for optimum results. Our objectives were to determine optimum application timing based on tree developmental stage, and to assess the overall effect of Ecolyst on yields, tree health, and grove profitability. Ecolyst was applied during Spring 2000 to 2 commercial blocks of Hamlin and Valencia oranges. Application times included: 1) prebloom; 2) 25-50% flowering; 3) full bloom; 4) petal fall; and 5) initial set. These times were chosen to determine if Ecolyst has effects on leaves alone, flowers and leaves, or leaves and fruitlets alone. Fruit were harvested in 2 locations at 4 dates and juice Brix, titratable acidity and ratio of Brix:acid determined. Early application of Ecolyst was most effective for increasing juice Brix by an average of 0.28°. Ecolyst increased Brix on 3 of the 8 harvest dates. Ecolyst did not affect any other fruit quality factor, tree vigor, health, or yields.

Objectives

Summary of Accomplishments

Ecolyst (6 g/acre) was applied to mature Hamlin and Valencia orange trees in Bartow and Lake Wales, Florida, in Spring of 2000. Applications were made at 5 different stages of flowering/fruit set from prebloom until initial fruit set. Ecolyst increased juice Brix on average by 0.28° and was effective on 3 of 8 harvest dates at the 2 locations. The reason for the variable response is unknown. The experiment was repeated in Spring 2001 using the same trees and application timings to determine if the product has cumulative effects. Ecolyst had no effect on juice acid, fruit size, yields, or tree vigor or appearance. Ecolyst has the potential to be of importance to the processing orange industry in Florida, but needs to be more consistent in its performance.

Funding:

FCPRAC Grants $24,000
Agency Contribution $30,000
Other Grants $20,000

Investigators: L. Gene Albrigo; William S. Castle; Ronald P. Muraro; L. W. Timmer; T. Adair Wheaton, IFAS - UF - CREC
Howard W. Beck ; James J. Ferguson; J. David Martsolf; Fedro S. Zazueta, UF - Gainesville

Progress Report for FY 00-01, Year 1 of 2.

Abstract

Making decisions about the best production practices, their timing and integration of options, has become very complex. Growers can use help-guides to effectively consider all of the options. Expert systems tied together on the basis of vegetative and fruit development stage can help to clarify and suggest timely options, provide production practices record keeping and free up time for other management decisions. Several units for the eventual integrated decision support system for citrus were developed to the stage of functioning prototypes during the early years of work. During this year’ s support, the Copper Spray Schedule was tested for the third year by growers and the data collected for flowering intensity and bloom date was modeled and incorporated into a flowering expert system to be tested in 2001-2002.

Objectives

Summary of Accomplishments

The Cu Spray Scheduling System for disease control was validated by grower tests and Cu residue analysis for a third year. Data was collected to add additional cultivar growth curves; some data was available to add temperature effects on rate of fruit growth. The Production Practices Scheduling System was improved and further developed through interaction with 3 grove production operations. Grower requirements for record keeping continue to be emphasized and will be tested in 2001-2002. Most work has concerned climatic effects on flowering intensity and time of bloom. Flowering data has been modeled and a flowering expert system was developed to run in 2001-2002. The production practices prototype will run and have grower testing in 2002. Several growers continue to cooperate in the integration of production practices, development of appropriate record keeping and improvement of the user interface.

FCPRAC Grants $ 32,500
Agency Contributions $ 44,500
Grower Contributions-Time $ 20,000

Total $ 97,000

Ten percent of 2 faculty, plus 5 percent of 3 growers’ and 10 percent of 1 grower’s time were used. Other infrastructure support was supplied at two locations of the University of Florida.

Investigators: J. D. Whitney; T. A. Wheaton; W. S. Castle; S. H. Futch; J. K Burns, IFAS - UF - CREC
R. E. Rouse,IFAS - UF - SWFREC

Progress Report for FY 00-01, Year 1 of 3-5 years.

Abstract

Controlling tree size and maintaining good fruit production have been a problem in some orange plantings, particularly in cases where vigorous scion/rootstock combinations have been planted at close tree spacings. Fruit production is usually high early in the life of these plantings, and then becomes marginal after the trees have reached containment size. Low fruit production not only reduces gross returns but further reduces net returns because the per box harvesting costs can be higher.

Hedging, topping, nutritional, irrigation and tree thinning treatments have been under investigation to improve production and improve manual harvesting. The effects of many of these treatments on fruit yields and quality in Florida are not known.

Summary of Accomplishments

This was the final year that data (5 years total) were collected in Experiments 1 and 2 in FCPRAC 951-23 and are included in this report.

In the hedging/topping/skirting experiment (Experiment 1) in 15 ft tall Valencia Rohde Red/Carrizo trees, fall topping had higher box and lb solids/acre yields than did spring topping for the third consecutive year. After October hedging and topping, some young flush was killed by 3 January freezes (grower recorded lows in the mid 20s). Angle topping had higher box and lb solids/acre yields than did flat topping.

In the adjacent nutrition (nitrogen)/irrigation experiment (Experiment 2) in the same Valencia grove, irrigation (no irrigation 7/00-2/01 vs. grower irrigation year round) and nitrogen (130 to 220 lb/acre) effects were not significant. The droughty conditions in fall 2000 and the lack of differences in these data and similar data from previous years all provide evidence that these trees (particularly those with no irrigation at 130 lb N/acre) on 2-row beds may have been receiving a substantial portion of their nutrients and water from the water table below the root system. Manual harvesting rates were positively correlated with box/acre yields at an average fruit size of 154 fruit/box.

In the 11-year-old 24 x 8 ft Hamlin/Carrizo tree thinning experiment (Experiment 5), the 12/98 clipping of every second and every third trees reduced lb solids and box/acre yields for the second subsequent season compared to solid hedgerow. A similar thinning experiment was initiated (trees clipped 5/00) in 11-year-old 24 x 8 ft Valencia/Swingle trees. Unexpectedly, as with the thinned Hamlin trees last season, per tree yields of the thinned Valencia trees for the first season after thinning were less than the hedgerow trees.

FCPRAC Grants                                                 $21,865
IFAS Contribution                                             $25,000
Orange Service Co. Pruning in-kind donation $ 7,000

Investigators: J. D. Whitney; T. A. Wheaton; W. M. Miller, IFAS - UF - CREC
J. K. Schueller,IFAS - UF - Gainesville

Progress Report for FY 00-01, Year 2 of 3.

Abstract

Although citrus growers usually manage their groves on a whole grove or block basis with uniform production inputs, considerable variability in various grove characteristics may exist. Some of the characteristics critical to management decisions are fruit yield and quality, tree size and health, soil type and fertility, leaf analysis, pest populations, water requirements, etc. Precision agriculture techniques can provide the tools that will allow grove owners to determine these characteristics in site-specific areas within the grove. Using these characteristics, the grower can then make decisions on adjustments to cultural practice inputs that will increase profits and apply the inputs in site-specific areas with precision agriculture equipment. Accurate yield maps are essential for determining profits/losses in site-specific areas and for determining whether changes in cultural practice inputs improve profits.

Objectives

Summary of Accomplishments

We integrated components of a GeoFocus, Inc. yield monitor unit with an automatic triggering system that actuated the yield monitor to record a DGPS location each time a fruit tub was loaded on a goat truck. The system replaced the need for the goat truck operator to push a button which is often forgotten and a source of error in citrus yield mapping. In field tests with a commercial harvester, the triggering system functioned satisfactorily but the GeoFocus unit would record no information if the DGPS signal was not available. We designed, fabricated, and field tested our own system by integrating an automatic triggering system, a microprocessor, and a DGPS unit. Missed tub locations were 2% or less in commercial harvesting operations. Progress was made on a method of dynamically weighing fruit as it was loaded in the grove. Ultrasonic and laser sensors were tested and found to give reasonably good measures of tree canopy sizes. The laser sensor also has good potential for measuring foliage density that could provide an index of tree health. We have continued to work with interested growers to identify reasons for spatial variability in yield and tree size/health, and to determine the reasons and possible remedial actions. In most cases, the variability has been related to soil characteristics and/or water drainage. An analysis was made of errors resulting from implementation of variable rate fertilizer applications. The CREC hosted a precision agriculture workshop October 10, 2000.

FCPRAC Grants $ 35,000
IFAS Contribution $ 65,000
FDACS Grant $ 5,000

Total $105,000

Investigators: Thomas Obreza; Robert Rouse, IFAS - UF - SWFREC

Progress Report for FY 00-01, Year 3 of 5.

Phosphorus movement to surface water and nutritional effects on fruit quality emphasize judicious use of P fertilizer. Citrus response to P is rare because it usually accumulates in soil. A calibration experiment using modern soil extractants was started in 1998 in a newly-planted citrus grove that was very low in soil-test P and K. A range of P and K fertilizer rates were applied to generate a wide range of soil-test P and K. Tree growth and fruit yield were measured and related to soil tests. This research will enable the Florida citrus industry to more appropriately allocate P and K fertilizer costs, minimize impact on surface water quality, and produce higher quality fruit by understanding the main effects and interactions of P and K.

Summary of Accomplishments

In autumn 1997, Flame grapefruit and Hamlin orange trees were planted at the SWFREC-Immokalee. Three-tree plots have been fertilized with four rates each of P2O5 and K2O to establish a range of soil test values. To assess fertilizer effects in 2000-01, soil and leaves were sampled in July, canopy volume was measured in September, and the first grapefruit yield was measured in February.

Mehlich I soil test P increased from Very Low to Very High as P fertilizer increased from 0 to 200 lb P 2O5/acre. Since P had accumulated in the soil, P fertilization was discontinued for the 2001-02 season. Soil test K only slightly increased (from Very Low to Low) as K fertilizer increased from 0 to 400 lb K2O/acre. Increasing the P or K fertilizer rate resulted in progressively higher leaf tissue P and K concentrations. This effect was much stronger for K than for P.

Grapefruit tree canopy volume increased from 230 to 319 cu. ft. as K fertilizer increased from 0 to 200 lb K2O/acre, while yield increased from 3 to 15 lb/tree as K fertilizer increased from 0 to 400 lb K2O/acre. Fertilization with P did not positively affect tree canopy volume or grapefruit yield.

The continued failure of K to accumulate in the soil will support the current practice of annually applying K fertilizer at similar rates as N. The lack of tree response to P fertilizer is surprising considering the very low soil test P in the control plots.

FCPRAC Grants $ 6,000
Agency Contribution (IFAS citrus grove and grove care, salaries) $12,000
Other Grants (Foundation for Agronomic Research) $ 2,000

Total $20,000

MANAGEMENT/PHYSIOLOGY

Investigator: Masoud Salyani, IFAS - UF - CREC

Project Report for FY 00-01, Year 1 of 1.

Sprayer air volume/energy, air distribution in open area and within canopy, and spray deposition were measured, using a Curtec, PowerBlast (4 fan sizes), and Titan tower (2 fan speeds). Ground speed and volume rate ranges were 0-4 mph and 26-384 gpa for air velocity and deposition measurements, respectively. Weather data were recorded during all experiments.

Air velocities decreased as ground speed increased. Mean deposition of Curtec was affected by spray volume and deposition increased at higher rates. With PowerBlast, spray volume did not have a significant effect on mean deposition but the fan size did. With Titan, deposition was affected by spray volume but not by the fan speed. The interaction between air volume and spray volume was significant in PB applications. The results suggest that high air volume rates may not give significant increase in spray deposition. The air and spray penetration largely depended on the tree canopy structure and prevailing wind direction.

Objectives

Summary of Accomplishments

FCPRAC Grants OPS Technician $13,500
Operating Expenses $ 6,500
$20,000  IFAS/CREC
Eng. Technician 50%
P. Investigator 25%

Other $ 0

Investigators: Fritz Roka, UF - IFAS- SWFREC

Ronald Muraro, UF - IFAS - CREC

Progress Report for FY 00-01, Year 1 of 1.

Abstract

Citrus growers face a variety of tree replacement strategies ranging from annual resetting individual trees to pushing and replanting entire blocks. A generic recommendation, which would define the most profitable course of action, is difficult, if not impossible given the number of horticultural and economic variables that need to be considered. This project develops a decision-aid tool, which incorporates a grower’s individual economic and production situation, and analyzes alternative tree replacement strategies.

A preliminary citrus reset analysis program has been developed and is being circulated for review. Additional material is available outlining data requirements and output results. The current model is the third revision and has evolved from interviews with selected growers. Default values for input costs and tree yields are imbedded in the model. Annual budget data provide a guide for input costs and an ongoing yield study in southwest Florida provides a basis for yield estimates by tree age.

Multiple reset strategies can be specified. Tree replacement scenarios are compared by estimating a 15-year cumulative cash flow. The program allows a grower to input specific cost and production values that match their specific situations. The program also allows a grower to input their best guess as to future market conditions.

The model has already been used to demonstrate that, under conditions of individual tree decline (i.e., CTV, blight, etc.), an annual reset strategy returns the highest cumulative net cash flow. This result assumes that the only decision is when to replace a tree and not whether to change scion variety or grove infrastructure (i.e., irrigation, tree density, drainage flows, etc.). The model’s value as a decision making tool increases under conditions of general grove decline, or when changes to grove infrastructure, variety and/or rootstock selections are being considered.

A final round of field testing is underway and computer programmers are being consulted to improve usability and model performance.

FCPRAC Grants $14,445
Agency contribution (IFAS) $12,000
Other Grants $ 0

Total $26,445

Investigator: Brian J. Boman,UF - IFAS - IRREC

Progress Report for FY 00-01, Year 2 of 2.

Abstract

This project investigates the effects of irrigation management and soil water status on tree response for both young and mature flatwoods citrus. Tensiometers and EnviroSCAN capacitance sensors are used to monitor to soil moisture status. Moisture stress in the trees is determined with measurements of stomatal conductance. Measurements have been taken on stressed and unstressed trees under various evaporative demand, soil moisture, and water table conditions. Soil moisture and stomatal conductance will be correlated to develop stress indices for various water table depths, soil moisture content, time of day, and climatic conditions.

One experiment is being conducted on young Valencia on smooth flat Seville trees that were planted in 1998. Trees are watered with 4 regimes: daily, 3 times/day, every 3 days, and at a soil moisture of 15 cbar. Treatment effects are evaluated with tree growth and flush status measurements. Another experiment is in a Valencia on rough lemon rootstock block that is 12 years old. Irrigation treatments are either on a daily or twice per week basis. Measurements of stomatal resistance under various soil moisture and environmental conditions have been taken. Fruit yield and juice quality parameters will be measured at harvest.

Objectives

Summary of Accomplishments

Both the young tree and mature tree experiments were started in the summer of 1999 when the Enviroscan system, tensiometers, and irrigation systems were installed for both experiments. Rainfall, since the study began, has been significantly lower than the long-term normal, requiring frequent irrigations. Growth measurements taken at two-month intervals on the young trees have shown that increases in trunk diameter were similar for all treatments throughout the first year of the study. Multiple irrigation per day has resulted in essentially the same trunk growth as the once-a-day treatment. By May of 2001, the treatments watered once or more daily had 10% more trunk diameter increase than the tensiometer and 3-day irrigation interval treatments.

Canopy growth was similar for all treatments for most of 1999 and 2000. By March of 2001, the daily irrigation regime had resulted in resulted in the greatest canopy development. Canopy diameter for the daily irrigation was about 6% more than the 3-day or 3-times per day treatments and about 10% more than the trees with tensiometer-controlled irrigations.

In the mature Valencia experiment, soil moisture, weather parameter, and stomatal resistance measurements have been taken under a variety of conditions to characterize stress levels. Yields in April of 2001 showed the higher irrigation rate to have about 13% higher yields than the low irrigation level. Yields and juice quality measurements will be taken at the normal harvest time in the spring of 2002 to conclude the experiment.

FCPRAC Grant $18,000 (FY 2000)

IFAS Contribution $18,000
Other grants $12,000

Top of Document  |  FDACS Contents Page

PLANT PATHOLOGY

Progress Report for FY 00-01, Year 1 of 3.

Abstract

Interactions of several stress agents in Florida citrus groves exacerbate Phytophthora diseases, even on a normally resistant rootstock like Swingle citrumelo. A more aggressive species of Phytophthora, P. palmivora, attacks Swingle, as well as Carrizo citrange and other rootstocks infested with Diaprepes abbreviatus on heavier, calcareous soils in other areas of the industry, even in absence of Diaprepes. Specific methods for identification and evaluation of Phytophthora resistance and tolerance to Diaprepes and marginal soils are proposed. The goal of this project is to continue research directed toward providing rootstock options for management of root weevils and other prevalent soil stress agents in Florida groves. This will be accomplished through greater resistance of rootstocks to Phytophthora spp. to increase tolerance of soil and pest interactions.

Objectives

Summary of Accomplishments

A Diaprepes-infested grove planted on poorly-drained soils types with damaging populations of Phytophthora palmivora and P. nicotianae was selected for intensive sampling of Diaprepes and Phytophthora populations in relation to maintenance of tree health with Ridomil Gold. Nova tangelo trees on Cleopatra mandarin did not decline between Oct 1999 and May 2000, while trees in alternating beds of Sunburst tangerine on Swingle citrumelo declined significantly. Relative abundance of Diaprepes adults from 99 locations did not differ between trees on the two rootstocks indicating that larval feeding pressure was similar. Populations of P. nicotianae from the same 99 sites were also similar on the two rootstocks, while populations of P. palmivora were significantly higher for trees on Swingle than Cleopatra. Higher populations of P. nicotianae from Swingle were correlated with greater recovery of Diaprepes adults from these tree locations. Decline in tree condition on Swingle citrumelo was correlated with P. palmivora populations but not with P. nicotianae. For Swingle, the interaction with P. palmivora results in tree death while health of trees on Cleopatra is maintained with applications of Ridomil Gold. These relationships indicate that the interaction of P. nicotianae is with fibrous roots during the initial stages of root attack by larvae and that the interaction of P. palmovora is with advanced stages of structural root attack. The differential susceptibility of Cleopatra vs. Swingle to the Phytophthora palmivora/Diaprepes complex is further justification for seeking sources of resistance to P. palmivora in citrus species such as mandarins and pummelos.

FCPRAC Grants $ 44,900
Agency Contribution $120,000

Other grants $ 20,000

Investigators: P. D. Roberts,IFAS - UF - SWFREC
T. R. Gottwald,USDA-ARS, Ft. Pierce
P. J. Sieburth,FDACS - DPI
S. M. Garnsey,IFAS - UF - CREC

Progress Report for FY 00-01, Year 2 of 3.

A disease problem of unknown etiology that causes severe bark flaking in grapefruit was found in several commercial groves in SW and central Florida in 1998 and in additional groves in subsequent years. Trees exhibiting symptoms are typically 4-7 years. Affected grapefruit varieties are White Marsh, Rio Red, and Flame. Trees are on Carrizo, Swingle, and Rough Lemon. An associated decline is reported and trees with flaky bark were removed on 400 acres. Initial investigations into the cause of the flaky bark symptoms were negative for any insect or pathogen, environmental stresses, nutritional or pH related damage. Observed trees showed a slow increase in disease incidence and severity during from 1998-99 indicating spread and persistence of the disease. Identification of the cause of the flaky bark disease and its impact on trees will lead to understanding and control of the problem.

            1. Identify the cause of the flaky bark disease.
            2. Measure the increase and spread of flaky bark symptoms.
            3. Determine the impact of flaky bark on tree health related to decline and yield.
            4. Determine the extent of the problem on citrus in different production regions beyond Central and Southwest Florida.
            5. Formulate control methods.

Plots were established at three groves containing symptomatic trees. Each tree in a 20 x 20 tree plot was visually assessed for presence of flaky bark and rated for severity. Trees were re-examined after 6 months and will be monitored at yearly intervals. Trees exhibited an increase of flaky bark incidence and severity confirming preliminary data of persistence and spread of the disease. The data collected during 3 years will be analyzed by temporal and spatial modeling programs to characterize whether spread is consistent with movement via a vector, mechanical transmission, or occurs randomly.

To determine whether an insect pest or fungal or bacterial pathogen is involved, trees at 2 test sites in 4 replicate plots of 5 to 10 trees were sprayed on the lesions with at a solution of copper and Ridomil or an insecticide. Control trees were untreated. Trees are being monitored for any change in symptoms using the methodology described above.

Both control and inoculated trees in the transmission studies established in 1998 showed symptoms in 2000-01. Additional inoculations were made or will be made to other varieties in the field and greenhouse trials. Development of symptoms will indicate a transmissible agent.

Non-pathogenic factors and association continue to be examined. Fungi and bacteria were isolated from diseased samples. Only one fungus was consistently recovered but it is also a common saprophyte; its pathogenic role is under investigation.

Additional sites were identified but none are beyond central and southwest Florida.

FCPRAC Grant $21,500
UF, SWFREC $ 0
Other Grants $ 0

Investigator: Kenneth Derrick, IFAS - UF - CREC

Progress Report for FY 00-01, Year 2 of 3.

Abstract

The Florida citrus industry loses more than 600,000 bearing trees per year to citrus blight. There are no reliable methods for controlling blight and the cause of the disease is unknown. The symptoms associated with citrus blight can be reproduced by root graft inoculations, which indicates the disease is caused by a pathogen. A major research objective is to induce symptoms of blight in producing trees in a grove or in plants in the greenhouse by inoculations using either cultures of microorganisms or extracts from roots of trees with blight. Blight associated protein p12 is always present in trees with blight and appears to be involved in cell growth. Research is in progress to determine if p12 produced by the tree in an effort to resist the disease and with transgenic expression of the p12 gene in scions and rootstocks provide resistance to blight. In addition, using cDNA subtraction methods, we have found several additional genes that are either up or down regulated in blight affected trees.

Objectives

Summary of Accomplishments

We have developed an efficient Agrobacterium-mediated transformation system for citrus. The p12 gene has been used to produce transgenic rootstocks (rough lemon, Carrizo citrange) expressing both sense (p12 producing) and antisense (blocking p12 production) directions. Some of the transgenic plants have multiple copies as shown by Southern blots. Further evaluations of these plants are in progress. Selected plants will be increased to produce trees for field trails for resistance to blight. This past year we have made a search for additional genes that are either up or down regulated in response to blight using cDNA subtraction methods. Numerous genes that are affected by trees with blight have been identified, some of which are expected for diseased plants and some of which are of unknown function.

Numerous trees have been inoculated with either cultures or extracts from roots of trees with blight. These trees are being monitored by p12 assays and observed for symptoms of blight. Attempts to associate pathogen DNA with blight are being made using DNA subtraction methods.

FCPRAC Grant $56,822
OE from IFAS $ 1,500

Total $58,322

Project No. 003-11P
Investigators: Harold W. Browning

Stephen M. Garnsey, IFAS - UF - CREC

Progress Report for FY 00-01, Year 1 of 3.

Abstract

The proposed research will generate a risk-based framework from which decisions can be made on relative importance of citrus diseases and what research needs to be done to address the most critical questions. This approach could be expanded to other research areas beyond the introduction of Exotic Diseases, making it a model for risk assessment and prioritization of research.

Objectives

Summary of Accomplishments

A list of 17 exotic citrus pathogens was selected for evaluation after review by Florida citrus pathologists. Criteria for an objective evaluation of exotic pathogen threats were also reviewed and 21 factors in six major categories were selected. Evaluation forms suitable for the different types of pathogens were developed and tested with a select panel of Florida scientists. The final evaluation process developed reflected numerous inputs received in the initial test. The process includes development of background information sheets for each pathogen, and independent rating of each pathogen for 21 criteria by members of a select working group. This group includes scientists with expertise in pathology, entomology, genetics, molecular biology and economics, and where possible, working experience with each disease. The independent ratings are compared and a consensus scoring is developed in a joint meeting of the working group. Evaluations have been done for five diseases and the system worked well. We are now preparing the background information sheets needed to complete the evaluation of the remaining diseases this fall. We are also noting needs for research that will improve knowledge of exotic pathogens and their control. An Exotic Pests of Citrus Technical Advisory Task Force (EPCTATF) was established in May by the Florida Department of Agriculture and Consumer Services. The Task Force chairperson has been advised of the activities of this project and invited to participate in our evaluation efforts.

FCPRAC Grants $ 20,000
Agency Contribution 0
Other Grants $ 0

Investigators: William Dawson ; S. Gowda; Dennis J. Lewandowski, IFAS - UF - CREC

Progress Report for FY 00-01, Year 3 of 5.

Citrus tristeza virus (CTV) has caused considerable damage to citrus in Florida by killing trees on sour orange rootstocks, and there is a continuous threat of introduction of stem pitting strains that could destroy the economic viability of the industry. This research program is designed to provide new methods to manage diseases caused by citrus tristeza virus. Cross protection has been a practice that has allowed citrus production in areas with severe stem pitting diseases. However, this procedure which relied on finding some natural strain that would protect against a severe strain has not been effective in Florida. New technologies now allow approaches that have not been possible previously. We are genetic engineering "ideal" mild strains to use to cross protect existing citrus planting and new plants before resistant plants are available against decline and stem pitting diseases. The overall objective is to remove CTV as a threat to citrus production in Florida.

We are attempting to create "ideal" cross protecting isolates of CTV by genetic engineering which can be used to inoculate trees against disease. This is a difficult and labor intensive effort, but we have made considerable progress toward this goal. In the first phase of this project, we developed genetic systems necessary to allow manipulation of the virus. We completed sequencing the two prevalent Florida strains, the decline CTV isolate (T-36) and the mild CTV isolate (T-30). Both have been assembled into a series of full-genomic cDNAs from which RNA transcripts can be produced in the test tube to infect protoplasts. We can now manipulate the virus and put the altered virus back into citrus trees. This completes the most difficult components of this project. This now allows us to identify sequences of the virus that cause disease and cross protection and to design protecting strains. We have ongoing experiments to examine the mechanism of cross protection. We have created several mutants of CTV and are determining whether these mutants can exclude the severe virus from infecting citrus trees. We are racing to have protecting isolates available to protect against any new severe isolates that begin threatening Florida citrus and to allow use of the sour orange rootstock wherever needed.

FCPRAC Grants $ 47,590
Agency Contribution 0
Other Grants $ 155,000

Investigators: Kenneth Derrick ; Gary Barthe, IFAS - UF- CREC

Progress Report for FY 00-01, Year 1 of 3.

Abstract

There is a need for methods for rapid indexing of citrus budwood for psorosis. Indexing for psorosis is now done by graft inoculation of citrus seedlings and observing leaf symptoms, which can be transitory and very mild. Also, there are some isolates that apparently do not induce any leaf symptoms, and bioindexing for psorosis is time consuming and subject to considerable error. Psorosis is one of the few remaining viruslike pathogens of citrus that cannot be indexed by nonbiological methods. We characterized an unusual spiral shaped virus, referred to as a spirovirus, that is associated with psorosis. We have had numerous requests from regulatory agencies and diagnostic laboratories for nonbiological methods for detecting this virus for use in citrus clean stock programs. This project is designed to meet that need. In addition, the virus associated with psorosis has some unusual properties that make it an ideal choice for use as a vector for expressing foreign genes in citrus. The most obvious advantage of using a virus vector for citrus is that foreign genes can be expressed in existing trees.

Objectives

Summary of Accomplishments

Several strains of the psorosis virus and some additional unknown infectious agents have been isolated from grove trees. Efforts are being made to characterize these unknowns using procedures similar to those that were used to characterize citrus psorosis virus.

The sequence of the viral genome segment that encodes for the coat protein has been determined for isolate CRSV-4 and is being used to make various RNA transcripts for potential use as a virus-based gene vector.

We have developed an efficient Agrobacterium-mediated transformation system for citrus. Constructs of the coat protein gene of citrus psorosis virus been made and will be used to make transgenic plants. This should be a model system for testing coat protein mediated resistance in citrus.

Reliable PCR based detection methods for several isolates of the virus that causes citrus psorosis were developed in this project. In response to call outs from growers to examine citrus trees showing bark scaling we are now making assays using the PCR methods for citrus psorosis virus and by biological indexing.

FCPRAC Grant for OE $20,000
IFAS provides salary for PI and one technician.

Investigator: Peggy Jane Sieburth, FDACS - DPI

Progress Report for FY 00-01, Year 2 of 3.

Further optimization of viroid PCR testing by determining tissue type and time of year that should be used for sweet orange, grapefruit, and mandarin types will be determined for each viroid. The presence and distribution of viroid I will be determined. s-PAGE equipment will be purchased and protocols written up to be ready for s-PAGE in year 3. New primers will be incorporated to improve the detection of viroids for which tests are not robust. The Florida citrus industry will benefit by improved testing to detect viroids in budwood sources.

The remaining 11 viroid inoculated field trees were planted out for use for the tissue and time of year studies. The leaf blade tissue and the wooded bark had the lowest concentrations of viroids. Viroid III replicated to higher concentrations than viroid II. It will be important to see if this also holds true for the time of year study. Samples for the time of year study for year 3 were sampled, extracted, and frozen for the months August through October of 2000 and April through July of 2001. A centrifuge, rotor, and adapters, as well as a vertical gel unit, were purchased to be used for s-PAGE research in year 3; s-PAGE protocols are in place. The sensitivity of detection of PCR products was increased by running acrylamide gels stained with silver and Gel Star stains as well as running Metaphor agarose gels. These 2 new detection methods have been essential for our detection of products from PCR for viroids IV, I, and the new CEV Primers. The new CEV primers appear to be promising and the annealing temperature was optimized with the new gradient thermocycler. A problem with false positives still needs to be resolved. These primers have been adapted to work with the same buffer concentrations as viroids II and III opening the possibility of multiplexing with primers for viroids II and III. This would triple the number of trees that could be tested for all 3 viroids.

FCPRAC Grants $23,500
Agency Contribution $16,000
Other Grants $ 0

Total $39,500
 

Investigators: T. R. Gottwald, USDA-ARS, Orlando
J. H. Graham, IFAS - UF - CREC

Project Report for FY 00-01, Year 3 of 3.

Abstract

Asiatic Citrus Canker (ACC) has spread from residential Dade Co. and infested residential and commercial areas of Manatee Co. to other locations in South Florida in spite of aggressive survey and eradication efforts. Outbreaks in commercial citrus areas were predominately traced back to the Miami infestation and presumably occurred due to human movement. In spite of significant removal of trees from the core areas of infestations, the inoculum has been spread repeatedly by hurricanes, tropical rainstorms, tornadoes and over long distances by humans.

Objectives

Summary of Accomplishments

Studies were conducted to determine the longevity and epidemiological significance of bacterial survival on plant material and inanimate objects in both shade and sun. Survival on most surfaces was 24 to 72 hours unless surfaces were kept moist and in the shade.

Bacterial aerosols were generated by chipping machinery and at landfills when debris was dumped. However, only the debris that escaped the chipping machinery was found to contain viable bacteria that initiated disease in trap plants. New chemical materials including Induced Systemic Resistance (ISR) compounds were evaluated for augmentation of traditional chemical and horticultural control strategies. The most promising compounds have been taken to Brazil for further field-testing.

Studies on bacterial spread in urban Miami determined disease gradients in Miami resulting from rainstorms. To accomplish this, nearly 19,000 trees were located via differential GPS, and assessed three times over 18 months to date infections. Spread from point sources of infection was calculated. The majority of the disease spread by rainstorms was contained within 1900 feet of known infected source trees. This research prompted USDA, APHIS, and the Citrus Canker Eradication Program to replace the 125-ft rule to define exposed trees by a 1900-ft rule in January 2000.

A sentinel tree survey method to locate citrus canker infections was also developed as another outcome of the epidemiology study. The method has been deployed, validated, and implemented statewide by APHIS and the Citrus Canker Eradication Program to find infestations before they spread.

FCPRAC Grants $ 43,745
Agency (USDA, ARS) Contribution $311,717

Other Grants (USDA, APHIS) $283,490 (not included

Total $355,462 in total)

Investigators: L. W. Timmer,IFAS - UF - CREC
P. D. Roberts, IFAS - UF - SWFREC

Progress Report for FY 00-01, Year 2 of 2.

Abstract

Postbloom fruit drop (PFD) has caused sporadic, but often severe, losses on oranges. Control with Benlate has not always been effective, but whether control failures have been due to resistance in the pathogen, poor timing of applications, or to highly favorable conditions for disease is uncertain. Greasy spot causes excessive defoliation and yield loss as well as reducing fruit quality. More complete information is needed on the best timing of spray applications and other materials need to be evaluated for control. Currently registered fungicides are not highly effective for control of Alternaria brown spot. Development of better methods of timing spray applications are needed to maximize the effectiveness of available products.

Objectives

Summary of Accomplishments

Isolates of Colletotrichum acutatum, the cause of postbloom fruit drop, were collected from 9 groves statewide (180 total) and assessed for sensitivity to Benlate. No resistant isolate was detected. The sensitivity of isolates from groves never sprayed with Benlate was the same as that of isolates from groves sprayed frequently. In greenhouse tests, Benlate was effective as a preventive application and as postinfectional sprays for up to 48 hours after infection, but Benlate did not kill ungerminated spores, prevent spore germination, or prevent spore production, but did reduce growth of the fungus significantly. Fungicide tests produced little data in 2000 and 2001 due to low disease levels.

In timing trials for control of greasy spot in Lake Alfred, LaBelle, and Ft. Pierce, a single well-timed spray of a copper fungicide was as effective as a two-spray program. However, the best month for application varied with year and location. Generally, for a single spray, June was the most effective timing and for a two-spray schedule, the June + August timing was best. A micronutrient spray + petroleum oil was nearly as effective as a copper fungicide. Peak ascospore release was not a good indicator for timing of sprays.

The Alter-Rater model was developed to assist in timing of fungicide applications for Alternaria brown spot. In the model, points are assigned for each day based on occurrence of rainfall, duration of leaf wetness and average daily temperature. In 2000, the Alter-Rater predicted from 4 to 10 sprays depending upon disease history and variety and predicted fewer sprays than the Copper Model to achieve the same control.

FCPRAC Grant $ 53,000

UF, CREC $ 85,000

Other Grants $ 5,000

Total $143,000

IFAS - UF - IRREC

Progress Report for FY 00-01, Year 2 of 2.

Abstract

PFD is a serious problem in several Florida citrus varieties, reducing yield when conditions are favorable for disease. The causal organism occurs on leaves, but large populations only develop on flower petals. Severe PFD is likely when prolonged bloom combines with regular rainfall to enhance initial infection, spore dispersal, and repeated secondary infection. In four years of study, GA applied at appropriate timings during late fall and winter has been demonstrated to reduce numbers of flowers, alter time of peak bloom, reduce bloom duration, and decrease or eliminate bouquet bloom. All of these factors should help reduce severity of PFD.

Objectives

The purpose of this research is to identify methods to concentrate the citrus bloom period and assess effectiveness in overcoming PFD reduction of cropping. Our specific goals are to:

Summary of Accomplishments

PFD development is enhanced by prolonged and heavy bloom, and is often difficult to control with fungicides. This project assesses use of PGRs to manipulate bloom and reduce susceptibility to PFD in Navel (3 years) and Valencia (2 years). 30 ppm GA was applied late-Nov, mid-Dec, early-Jan, late-Jan, as well as repeated applications of the 2 earliest timings, 2 latest timings and the earliest and latest timing. All GA treatments affected bloom intensity and some affected bloom timing. Following GA-treatment, total flowers/tree ranged from 8-60% of controls. Early GA treatments delayed bloom while late treatments produced earlier bloom, and the greatest shift in bloom timing occurred following 2 early or late applications. The most effective Navel treatments reduced duration of bloom by 30-43%. In Navels, peak bloom differed by 3 weeks between the earliest and latest treatments, while Valencia displayed a two-week differential. GA treatments had varying effects on yield/tree in 2000 Navels, with Dec 17 treatments increasing yields 42%, no effect of most treatments, and the double January treatment decreasing yield by 28%, but providing earlier maturity. Yield data on 2000 Valencia showed no reduction in cropping even with 90% reduction in flowering, but larger mean fruit size. No significant PFD has been observed during these

years of study, but reduced bloom and shift in bloom timing is likely to be beneficial in many years when PFD is a factor. Dormex treatments on Navel and Valencia resulted in some defoliation but no change in bloom timing or duration.

FCPRAC Grants $ 40,000
Agency Contributions $ 96,000
Grower Contributions-Time $ 10,000
Other Related Grants $ 40,000

Total $186,000

One faculty member and associated program at 15% of total time.

Top of Document  |  FDACS Contents Page

Investigators: Philip A. Stansly, IFAS - UF - SWFREC
Jorge Peña, IFAS - UF - TREC

Progress Report for FY 00-01, Year 1 of 2.

Abstract

Among the weapons in a limited arsenal against Diaprepes, long residual and compatibility with biological control are considered advantages of egg sterilization with Micromite® (diflubenzeron), over insecticidal control of adults. Micromite is often applied in summer for both rust mite and Diaprepes control. Under these conditions, the duration of residue effectiveness has not been evaluated. Information on the ability of parasitoids to develop in Diaprepes eggs sterilized with Micromite will benefit box tax funded introduction efforts. This research would provide the grower with guidelines for the most effective use of Micromite.

Summary of Accomplishments

The treatments were evaluated under two different field conditions, 27 Sept 2000 and 6 Jul 2001, in a grove of Hamlin orange trees in Hendry County. Diaprepes abbreviatus egg masses were collected weekly, and hatch rates evaluated from trees sprayed with either Micromite plus 1% crop oil or 3% crop oil alone, and compared to untreated trees. Diaprepes abbreviatus eggs in wax paper strips parasitized by the egg parasitoid, Ceratogramma etienne, were stapled to the foliage while treatments were applied 27 Sept. Treatments were applied with an airblast speed sprayer at 400 psi delivering 91 GPA. Under both growing conditions, there was a significant reduction of egg hatch rates for the first 27days in the Micromite treated trees starting less than 4% at 12 days after treatment and increasing to 56% on day 33, which was no longer significantly different from the untreated trees. The loss of Micromite efficacy generally followed the same rate for both periods despite over 7.5 inches of rain during the summer, while the fall period had only 1.4 inches of rain. The hatch rate for the 3% oil treated trees was similar to the untreated, however, fewer egg masses were laid in the oil treated trees for the first week. The treatments did have an impact on the emergence of the egg parasitoid, Ceratogramma etienne, from parasitized Diaprepes abbreviatus eggs. Oil reduced emergence of parasitoids when applied close to the time of emergence, whereas Micromite had its greatest effects applied when parasitoids were less mature.

FCPRAC Grant $ 9,500
Agency Contribution
BioScientist $ 5,500
Ag Tech $ 5,000
Secretarial $ 1,000
Supplies $ 800

Other Grants $ 0

Investigators: Stephen L. Lapointe ,Cindy McKenzie; Allen Weathersbee ; Tim Gottwald,USDA-ARS, Ft. Pierce

Progress Report for FY 00-01, Year 1 of 2.

Root-feeding weevils are a severe constraint to the profitability of Florida citrus. The lack of controls for the Diaprepes root weevil (DRW) necessitates new approaches based on emerging technologies. One of these is kaolin-based particle film technology, an invention of USDA-ARS. We recognized the potential application of this approach for control of DRW. In our laboratory, adult DRW were deterred from feeding, and oviposition was suppressed on Surround™- treated leaves. In 2001, we initiated efforts to demonstrate Surround’s effectiveness in the field, to establish the dose required for deterrence, and to determine feasibility under real weathering conditions. The expected output is a novel means of control for citrus root weevils in an environmentally appropriate and nontoxic manner that will contribute to the economic sustainability of Florida's citriculture. Specific objectives are outlined below:

Objectives

Summary of Accomplishments

Greenhouse studies wherein adult Diaprepes root weevil (DRW) were exposed to foliage treated with Surround WP (Engelhard Corp., Iselin, NJ), a kaolin-based particle film, demonstrated potential for breaking the cycle of DRW infestation by inhibiting oviposition. In cages, DRW were deterred from feeding; oviposition was suppressed on treated leaves (Lapointe 2000). Deterrence declined logarithmically with decreasing residue. Based on these results and FCPRAC support, we initiated field trials at 3 sites. A trial consisting of 168 Hamlin/Carrizo was established at USDA-ARS, Ft. Pierce, in 1999. This site has not been infested by DRW and tests the effect of Surround on tree growth and nontarget pests. Surround had a dramatic, positive effect on tree growth. Since planting, treated trees grew between 32 and 42% more that untreated trees (stem diameter). We continue to document this as well as fruit set, yield, and quality. Two trials were established in 2001. The 1st consists of 576 trees in a DRW-infested field at IFAS, IRREC, and the 2nd was established in a DRW-infested commercial grove (Sexton Grove Services). Through July, 2001, fewer egg masses were laid on Surround-treated foliage by DRW and blue-green weevils despite heavy rains. We expect a season-long reduction in oviposition of 70%. Trees will be destructively sampled in early 2002 to measure efficacy as determined by root damage and number of larvae/tree. As a result of this work, Engelhard Corporation will provide experimental formulations with increased rainfastness, and expects to market a kaolin-based product in Florida.

FCPRAC Grants $ 36,000
USDA-ARS Contribution
Salary of PI’s (20% of  SL, 5% each of CM, AW, & TG) $ 41,000
Salary, Technicians (25% of ASH/KM) $ 10,000
Spray booth $ 25,000
Supplies, vehicles, travel, greenhouse & lab  facilities, insect rearing, etc. $ 25,000 Other Grants $ 0

Total $ 137,000

Investigator: Carl C. Childers, IFAS - UF - CREC
W. Calvin Welbourn, FDACS - DPI

Progress Report for FY 00-01, Year 1 of 2.

Citrus rust mites and the fungal pathogen, greasy spot, are recognized as key fruit and foliar pests, respectively, on Florida citrus. Control approaches to date have focused on each pest separately instead of developing a more comprehensive control approach. Current economic issues require Florida citrus growers to seek alternative strategies to reduce their production costs. Four citrus growers (two Valencia and two Hamlin orange groves), previously on crop protection programs that included both copper formulations and acaricides other than petroleum oil, were switched to an IPDM (Integrated Pest and Disease Management) program beginning in early 2000 as part of a 3 year USDA CSREES grant. This FCPRAC grant was an extension of this research and Dr. Arturo Goldarazena was hired July 1, 2000, to assist in the project goals. The objectives were to determine the positive and negative effects resulting from switching spray programs in our test areas to 435 petroleum oil only sprays for greasy spot control versus the more expensive copper/acaricide programs used previously. An additional objective was to determine the time required to re-establish the beneficial mite complex within each of the 4 cooperator test sites. These efforts are directed at reducing grower spray costs, minimizing pest mite populations, and optimizing conditions for the beneficial mite complex.

Summary of Accomplishments

Each of 4 grove sites was monitored for pest and beneficial mites and greasy spot control versus the grower’s original programs. One of the 4 test sites required a Vendex application to reduce excessive rust mite buildup in addition to 2 petroleum oil applications during 2000. Three oil sprays were required at a second grove site after the first year. The other 2 sites had only 2 oil applications each. No additional pest mite or insect problems or excessive greasy spot infections developed in any of the 4 sites during 2000. Results, to date, are very encouraging using 435 oil only. An additional field experiment evaluated the impact of 2 new fungicides (Enable and BASF 500) and 2 acaricides (Micromite and Danitol) were applied as separate treatments to identify positive or negative impacts versus 435 oil only or copper only. No negatives have been observed to date with these 4 products. Copper formulations alone or with oil have been shown to flare pest mite populations. To date, only 435 oil has been tested and it does not result in pest mite increases following 2-3 applications per year. Beneficial mite populations in the 4 sites did not increase significantly in our test areas compared with the growers’ programs after the first year. Goldarazena has identified 13 species of Tarsonemidae on Florida citrus of which 4 are new. The taxonomic steps are critical in accurately identifying the species that occur on Florida citrus. Most are believed to be fungivores and one or more may offer potential as biological control agents of fungal pathogens. Feeding studies will be initiated in January 2002.

FCPRAC Grants $ 30,000
IFAS Contribution $ 50,000
USDA CSREES $ 50,000

Investigators: Clay W. McCoy, Robin Stuart IFAS - UF - CREC

Progress Report for FY 00-01, Year 1 of 3.

Abstract

The Diaprepes problem in Florida is extensive, the insect continues to spread at an alarming rate. Larval feeding on the roots can cause tree loss and/or decline directly, or indirectly by opening infection courts for root rot diseases. Economic management of this pest and soil diseases is vital to grower success. For some time now, chemical and biological tools have been tested, and registered for grower use against weevil larvae and adults. Suppression of the larvae and adult weevils with chemicals and biologicals has been documented via research. However, these suppressive methods cannot guarantee grower profitability.

In 2000-2001, our research focused on the following three objectives that should benefit the grower in his attempts to manage Diaprepes economically.

Objectives

Summary of Accomplishments

After 3 years comparing different weevil management strategies (foliar, soil, foliar plus soil and no treatment) with and without Phytophthora control in a flatwoods grove, the following trends have been detected based on weevil monitoring, fibrous root density and fruit yield measurements: 1) Diaprepes and Pachnaeus co-exist in the grove at moderate levels with adult emergence for both species occurring only from mid-April to mid-June; 2) Two foliar sprays timed to early May and June reduced adult numbers temporarily but had no apparent long-term effect on yield; 3) Capture as a soil barrier and two applications of nematodes for larval control had no significant effect on fibrous root density and fruit yield compared to the untreated control; and 4) Ridomil applied twice per year was not significantly different from no Ridomil, although the 3-year trend suggests possible change in the future.

Spring and fall field trails were conducted to determine the efficacy of two species of entompathogenic nematodes for control of larvae of Diaprepes in a citrus grove with sandy clay loam (alfisol) type soil. Both BioVector 355 as a water-dispersible granule and GrubstakeTM 100 as a paste on sponge at rates from 20,000-100,000 IJs/ft2 failed to reduce larval populations in the tree rhizosphere at 25 days post-treatment.

Funding:
FCPRAC Grants $ 20,000

Total $160,000

IFAS - UF - CREC

Sam E. Simpson

FDACS - DPI

Progress Report for FY 00-01, Year 3 of 4.

Abstract

Better and more lasting control strategies for Diaprepes root weevil control are an important and essential tool for Florida citrus growers. Presently, control methods are limited or not effective for the desired effect. This proposal investigates the effectiveness of spray oils on reducing or interrupting egg deposition, and determining proper dosages of a variety of pesticides for adult weevil control. These investigations can provide the grower with the most efficient and effective pesticide needed for adult weevil control.

Objectives

Summary of Accomplishments

This project made progress faster than any other project we have had funded by FCPRAC. We have developed a pesticide bioassay for oral dermal toxicity. We have bioassays 25 pesticides and have determined that 13 of these would be effective within 72 h of application. These compounds are Fury, Imidan, Lannate, Pounce, F0510 (a pyrethroid) Supracide, Vydate, Avaunt, Capture, EXP 61685 (Fipronil derivative), Fipronil, Furadan, Baythroid, and Carzol. We have data that if given a choice Diaprepes will lay eggs on foliage which have not been treated with petroleum spray oil. Eggs and egg masses were about one-fourth compared to controls. This project will be completed in 2001-2002.

FCPRAC Grants $ 48,000

UF - Gainesville

Dr. Ru Nguyen

DPI - Gainesville

Progress Report for FY 00-01

Length of Project: about 4 years

The Asian citrus psyllid was discovered in June 1998 in Florida. By June 1999, it had spread to 12 counties and by June 2000, it was in 21. We imported two parasitoid species from Taiwan and Vietnam in November 1998. We evaluated both species and submitted our application in June 1999 to state and federal regulatory authorities to release the first species (Tamarixia radiata). The first releases of T. radiata took place on July 15, 1999. Between July 15 and December 1999, approximately 12,000 T. radiata were released. Permission to release the second species, Diaphorencyrtus aligarhensis, was obtained on March 10, 2000, and releases were made during the 2000 growing season along with releases of T. radiata. Surveys indicate T. radiata is persisting and spreading. Surveys conducted during August-October 2001 will resolve further the distribution of T. radiata and D. aligarhensis.

We hope to discover the pink mealybug while it is still in a relatively small area in Florida. Two parasitoids are potentially available for importation, rearing and release.

When this project began neither pest was present in Florida, but both were targets of classical biological control programs because effective natural enemies are known. This project began January 1, 1998.

The Asian citrus psylla was found in Southeast Florida in June 1998. By June 2001, this pest could be found in all citrus growing areas of Florida. Parasitoids of the psylla were identified in Taiwan, Thailand, and Vietnam, and we imported them and developed rearing methods. In addition, we developed a molecular test (polymerase chain reaction) to confirm the absence of greening disease in the psyllid colony and in the imported parasitoids.

We evaluated the host range of T. radiata and D. aligarhensis, obtained permission to release T. radiata on July 12, 1999, and made the first releases on July 15, 1999. By December 1999, approximately 12,000 T. radiata had been released. Between August 1, 2000 and August 1, 2001, we released an additional 16,233 T. radiata in as many sites as possible, focusing especially on the newly infested areas.

On March 10, 2000, we obtained permission to release D. aligarhensis and are releasing both parasitoid species during the 2000 growing season; a total of 3239 D. aligarhensis have been released during the past year.

We continue to watch and wait for the pink mealybug. As soon as it is confirmed present in Florida, we expect to import and evaluate parasitoids for release in Florida.

FCPRAC Grant $ 32,000

UF - Gainesville

Dr. Ru Nguyen

DPI - Gainesville

Progress Report for FY 00-01

Length of Project: ca. 4 years

The brown citrus aphid is an efficient vector of virulent strains of citrus tristeza virus and also serves as a direct pest of young flush in citrus trees. Our goal is to identify host-specific parasitoids of the brown citrus aphid, import them into quarantine, evaluate them, and after approval by state and federal regulatory agencies, release them into Florida's citrus groves for permanent establishment. Lipolexis scutellaris, a parasitoid of the brown citrus aphid, was imported into quarantine in August 1999. Rearing methods were developed and a risk analysis was conducted; permission to release L. scutellaris was granted in June 2000 and the first releases took place on June 28, 2000. Between then and now (August 1, 2001) we have produced 23,308 L. scutellaris for release.

This project began officially on July 1, 1998. During 1999-2000, we maintained citrus trees in culture for rearing the aphids and clean aphid colonies. We identified parasitoids from brown citrus aphid in Vietnam and Guam and asked cooperators there to rear them for identification. In June 1999, the first shipment of Lipolexis scutellaris was sent from Guam to the quarantine facility in Gainesville and a successful colony was obtained in August 1999. Rearing methods were developed, risk assessments conducted, and an application was submitted to the Department of Agriculture and Consumer services for permission to release L. scutellaris in Florida. Permission was granted to release L. scutellaris in June 1999. First releases of L. scutellaris were made on June 28, 2000, in Gainesville and the first recoveries of adults occurred on July 10, 2000, indicating the first generation successfully had developed in the field. Since then, we have released approximately 23,000 L. scutellaris throughout the citrus growing areas of Florida. A disease problem in the

colonies arose during spring 2001, but we believe we have solved that and intend to release additional L. scutellaris during the 2001 growing season.

IFAS Contribution $33,000

ENTOMOLOGY

Investigators: Larry Duncan

IFAS - UF - CREC

Progress Report for FY 00-01, Year 1 of 1.

Abstract

A newly discovered Steinernema sp. is widespread in citrus orchards on Florida's central ridge. Steinernema sp. is most abundant during the early summer months and its activity declines during autumn. During the first weeks following application, Steinernema sp. is as effective against Diaprepes abbreviatus as the commercially available S. riobrave and it persists in soil longer than S. riobrave. Introduction of S. riobrave to soil displaced native Heterorhabditid spp., but not Steinernema sp. Due to the relatively short persistence of S. riobrave, displacement of native nematode species was correlated with reduced natural control of D. abbreviatus during intervals between nematode applications.

Objectives

Summary of Accomplishments

The new Steinernema sp. was described (Nguyen and Duncan, manuscript in review). Two orchards were surveyed between March and November by burying caged D. abbreviatus larvae and evaluating mortality after 7 days. In a grove on sandy clay loam soil (Poinciana site), we recovered Heterorhabditis indica. Monthly incidence of the nematode was correlated with numbers of D. abbreviatus eggs captured in funnel traps, consistent with density dependent response by nematode populations to insect availability. In a second grove on sandy soil (Bartow site), we recovered Steinernema sp., H. zealandica, H. indica, and S. riobrave at significantly higher levels than at the Poinciana site. Natural control by Steinernema sp. increases from May-July and declines significantly thereafter. The application of S. riobrave displaces H. indica and H. zealandica, but not Steinernema sp. Consequently, average mortality of D. abbreviatus larvae was 24% lower in plots treated with S. riobrave during all months except those in which nematodes were applied. These results suggest that use of nematodes with greater persistence than S. riobrave is desirable to avoid attenuating insect control during intervals between nematode application. Six months following application to soil, infection and reproduction by Steinernema sp. was significantly greater (double) than that by S. riobrave . There was no difference between efficacy of S. riobrave and Steinernema sp. during the first week after application. Surveys of orchards on the central ridge revealed widespread distribution of Steinernema sp. and the nematode was equally abundant in orchards with incipient and long-standing histories of infestation by D. abbreviatus.

FCPRAC Grants $18,000

Agency Contribution $19,500

IFAS - UF - TREC

IFAS - UF - CREC

Robert Bullock

IFAS - UF - IRREC

Clay McCoy

IFAS - UF - CREC

D. Hall

S. Lapointe

USDA, Orlando

J. Etienne

INRA, Guadeloupe

J. Knapp

IFAS - UF - SWFREC

Ru Nguyen

DPI, Gainesville

R. Adair

Kerr Center, Vero Beach

Progress Report for FY 00-01, Year 3 of 3.

Classical biological control of Diaprepes abbreviatus offers the promise of providing long-term, relatively inexpensive, control that can be part of sound management of the root weevil. This proposal investigates the success of biological control of Diaprepes abbreviatus in citrus orchards through exploration, collection, identification, and introduction of exotic egg and adult parasitoids of the root weevil from regions where species of Diaprepes are maintained under sub-economic damaging levels. Promising biological control candidates are mass-reared, released in citrus orchards, and their establishment evaluated in different citrus producing areas. If successful, biological control will reduce production costs by reducing pesticide applications in citrus orchards.

During 2000-2001, we obtained permission to release from quarantine Aprostocetus vaquitarum. Aprostocetus vaquitarum has been reared and 5,000 adults have been released in citrus groves located in 11 Florida counties. Releases of this new parasitoid are being monitored every 2 weeks on citrus groves. Another released parasitoid, Quadrastichus haitiensis, was considered established in Glades County, approximately 3 years after its initial release. This parasitoid has not established in other citrus growing counties in Florida. Candidate parasitoids, i.e., Pediobius spp., and Horismenus bennetti introduced by D. Hall and J. Eger from Belize, are currently being tested against D. abbreviatus under quarantine conditions. An exploratory trip was conducted in Cuba to collect and identify other parasitoids of the root weevil or related species. The adult parasitoid, Cenosoma spp., (Diptera: Tachinidae) was identified as a promising candidate for introduction into Florida. This candidate, however, could not be introduced at this time for the lack of necessary permits from the Cuban government to authorize its exportation. Efforts will continue to introduce this parasitoid into Florida.

Funding:

FCPRAC Grants $ 53,181

IFAS Contribution $152,000

Other Grants

NBCI, FNGA, SHARE $ 33,500

Reed E. Burns, Jr.

Richard D. Gaskalla

FDACS - DPI - Gainesville

Sam Simpson

FDACS - DPI - Winter Haven

Tim Holler

USDA - APHIS - Gainesville

Progress Report for FY 00-01, Year 2 of 2.

Abstract

Malathion and diazinon have been used for many years in Medfly eradication programs and for the Caribfly Fly Free Protocol. Increasing concern from the public sector, environmentalists, and the EPA about the continued use of these materials has placed renewed emphasis on identifying alternatives. This investigation will provide practical comparisons of alternative chemicals to malathion under field conditions and assess the effectiveness of diazinon as a soil treatment. These pesticides have been essential in the successful eradication of infestations or the rapid knockdown of high fruit fly populations prior to the initiation of Sterile Insect Technique. Field testing of alternatives following laboratory screening is necessary to confirm efficacy. Large plot field tests will be used for the comparison of chemicals and application methods. Bench top and field tests will be used for the assessment of diazinon and alternative soil treatment materials.

Summary of Accomplishments

Aerial applications by helicopter were applied to large (10 acre) replicated plots (4 reps) in citrus groves. The standard application of malathion (96.5% Fyfanon®) 20% plus Nulure® 80% at 12 oz mix/acre was compared to spinosad/SolBait (GF-120®) at 48 oz mix/acre and untreated controls. Plots were separated by a minimum buffer of 400 ft. Dyed, sterile, adult male and female Caribbean fruit flies were released in the plots prior to treatments. Efficacy data was obtained by comparing the number of trapped flies in each replicated treatment plot.

Aerial applications of spinosad/SolBait (GF-120®) were equally as effective in reducing adult Caribflies in citrus groves as the standard malathion bait spray currently used in Florida’s Caribbean fruit fly Protocol Program. Previous trials demonstrated that foliar spot applications of the spinosad treatment were also equally effective against adult Caribflies. The proposal to allow the Dow AgroSciences product, GF-120®, as an alternative to the standard malathion treatment for use in the Florida Caribfly Protocol Program is being recommended.

Techniques were developed for laboratory efficacy tests of diazinon soil drenches and comparisons with possible alternatives for use in fruit fly eradication programs. Diazinon at the standard EPA Emergency Exemption rate was compared to bifenthrin (Talstar GC®), lambda-cyhalothrin (Scimitar GC®) and spinosad (Conserve SC®) at the maximum labeled rate. Bifenthrin has demonstrated limited potential in these tests.

FCPRAC Grants $15,570

Agency Contributions ca. $50,821

Top of Document  |  FDACS Contents Page

Progress Report for FY 00-01

Year 1 of 1: extended 1 year

Circumstances within the Florida citrus industry in recent years (e.g., the demise of trees on sour orange from CTV) have given a new priority to the search for improved scion and rootstock cultivars, and more specific recommendations. The timely gathering and practical use of information and data to meet this priority is becoming increasingly difficult. Many new scions and rootstocks are being produced each year that require evaluation, and many commercial plantings are being established at the same time as research plots. Therefore, to effectively manage the expanding scope and magnitude of information and data available, we are proposing to create rootstock and plant breeding databases using Microsoft Access®. These databases will be the means to develop more site-specific rootstock recommendations of state-wide significance, and to operate a more efficient, productive cultivar improvement program, respectively.

A primary system manager was hired who is learning the Microsoft Access® software used in ths project. The primary data inputs have been identified and are being formatted. A preliminary list of commercial sites for collecting rootstock and scion information has been assembled with some follow-up contacts.

FCPRAC Grants $ 30,000

Agency Contribution $ 12,000

Total $ 42,000

H. W. Browning

D. J. Cantliffe

IFAS - UF - CREC

Core Lab Directors: J. W. Grosser and G. A. Moore

Progress Report for FY 00-01, Year 2 of 10.

Abstract

Several laboratories within IFAS and elsewhere are conducting basic research leading to the identification and cloning of individual genes that have potential to improve citrus cultivars for various traits including fruit/juice quality, disease and insect resistance, and cold-hardiness. However, most of these labs are not equipped and do not have the expertise or resources to transfer such genes to the appropriate citrus cultivars. Therefore, a core citrus transformation laboratory must be established to provide the service of transferring newly available genes to the appropriate citrus cultivars if the ongoing "revolution in plant biology" is to include citrus in a timely fashion. Once established, this core lab will allow the Florida citrus industry to efficiently leverage the millions of research dollars being spent on fundamental plant biology in the various research disciplines.

Objectives

Summary of Accomplishments

Following a national search, Dr. Vladimir Orbovic was selected to manage the core lab facility and he has since hired one full-time and another half-time technical assistant. The core lab is now fully equipped. Two methods of citrus transformation are being established in the facility. The first method is incubation of explants in Agrobacterium, known to be able to induce introduction of foreign genes into plant genome. Shoots regenerated from explants treated with bacteria are tested for presence of reporter gene inducing blue staining of transformed tissue. Through the multi-step procedure in vitro, shoots are grown into seedlings which are then subjected to test for presence of a gene of interest. Until now, 12 citrus cultivars were tested and some transgenic plants have already been produced. The second method involves the chemically induced transformation of embryogenic protoplasts. Transformed colonies are visually selected under the microscope by using the GFP (green fluorescent protein) reporter gene which produces a protein fluorescing green when irradiated with blue light. Transgenic colonies of two orange cultivars have been recovered and work is in progress to obtain first transgenic embryos. Efforts are now directed toward fine-tuning of both methods so that efficiency of transformation can be improved.

Dr. Orbovic will visit another core transformation lab (already functioning for other non-citrus commodities) early this fall, which should provide good insights on how to manage our lab. We expect to begin providing the service of citrus transformation to other researchers before the end of the year.

FCPRAC Grant $ 60,000

IFAS Contribution $ 60,000

Other Grants $ 0

IFAS - UF – CREC

Progress Report for FY 00-01, Year 1 of 3.

Abstract

The development of canker resistance in commercially important scions is critical to the future economic well-being of the Florida Citrus Industry. We propose to introduce genes (from the rice Xa21 gene family) that confer broad spectrum resistance to Xanthomonas oryzae (rice bacterial blight) in rice. Since the canker pathogen is in the same genus, these genes may have potential to function against canker in citrus. Initially, transformation experiments will be conducted with new embryogenic lines of superior Valencia and Hamlin sweet orange clones. Transformed colonies will be selected via expression of GFP (green fluorescence protein). Transformed plants will be selected via expression of GFP (green fluorescence protein). Transformed plants will be regenerated via somatic embryogenesis. Transgenic plants will be assayed for canker resistance by Dr. Jim Graham, using standard methods. Any transgene that is shown to significantly improve canker resistance in sweet orange will then be transferred to all commercially important Florida scions.

Objectives

Summary of Accomplishments

A citrus transformation vector-plasmid was constructed containing both the Xa21 resistance gene and the GFP (green fluorescent protein) reporter gene, each under the control of a different promoter. This was accomplished with some difficulty, as the original map provided with the Xa21 gene was inadequate. Transformation experiments were initiated, with emphasis on using the canker susceptible Hamlin sweet orange somaclone C1-46 embryogenic callus line. Transformation experiments with Valencia sweet orange somaclones B6-68 and T2-42, and C. amblycarpa mandarin were also conducted. Transformation was accomplished using our recently developed methodology-polyethylene glycol (PEG) induced DNA uptake by protoplasts, followed by GFP selection of transgenic colonies. Transformed colonies fluorescing "green" under blue light have been identified and recovered from these experiments, and they are currently being physically separated from non-transformed colonies. These experiments are ongoing, and additional transgenic colonies will be recovered as they are identified. Recovered transgenic colonies are being cultured on somatic embryogenesis induction medium containing maltose as the carbohydrate source to induce somatic embryo development, as necessary to regenerate transgenic plants. We expect to have transgenic plants containing the Xa21 gene during the coming year. A c-DNA clone of the Xa21 gene that does not contain the monocot (rice) intron has also been obtained from the University of California-Davis, and construction of a transformation vector-plasmid is underway. This c-DNA copy of the gene may have an advantage since we don’t know if citrus can properly process the monocot intron found in the wild type gene.

FCPRAC Grant $ 37,000

IFAS Contribution $ 0

(Will be continued in subsequent years as a part of 0110-03I Block Grant).

F. G. Gmitter, Jr.

W. S. Castle

IFAS - UF - CREC

Progress Report for FY 00-01, Year 8 of 20.

Abstract

The goal of this project is to develop the improved rootstocks that the Florida industry will rely on to remain competitive and profitable in the future, and to provide growers with information necessary to make the best rootstock choice for any situation. When new rootstock germplasm is developed and reaches an advanced stage of evaluation, the plant material goes into commercial trial, and appropriate data entered into formalized decision-making models. New improved rootstocks will help Florida growers to compete internationally. Tree loss and associated production losses, and tree replacement costs will be minimized. Citriculture will have a reduced impact on the environment through the biological control of diseases, thereby reducing chemical applications. New, widely adapted rootstocks will allow citriculture to expand into marginal areas. Overall, growers can expect savings in production costs, more continuous and higher productivity, and increased tree longevity.

Objectives

Summary of Accomplishments

Sexual Hybridization Program: From more than 25 crosses that were made at the diploid level in the spring of 2000 (using several trifoliate-derived parents onto sour orange-pummelo hybrids, or onto Ichang hybrids), 15 set fruit and over 1400 seeds were harvested and planted. Because polyembryonic seed were used, hybrids among the seedling populations are being identified morphologically. Fewer rootstock crosses were made during spring of 2001. Seed number/fruit was determined among >350 new citrange hybrids, as well as whether the seeds were mono- or polyembryonic. At least 70 citranges producing seedy polyembryonic seedy fruit were identified for further evaluation, and 8 seedy monoembryonic types were found which could be used for subsequent breeding cycles.

Somatic Hybridization Program: Continued propagation and planting of new material into blight hotspots (with Orie Lee), and as resets in other trials to replace poorly performing selections. Provided seed of 6 promising somatic hybrids to Reed Bros. Nursery for larger scale trials to be planted with Harold McTeer and Southern Gardens Citrus. Tetraploid Rootstock Breeding: Collected several hundred seed from crosses of somatic hybrid rootstocks (sour orange + Rangpur and Nova + HB pummelo as females); and selected 50 hybrids from 7 different parental combinations for further evaluation following screening (screening funded by the IFAS/USDA Cooperative Diaprepes agreement) for adaptation to high pH calcareous soils and Phytophthora resistance (6 hybrids also selected for salinity tolerance). Expanded the 2001 tetraploid crosses to include more pollen parents. Conducted extensive somatic fusion experiments (designed to build a sour orange replacement) by fusing C. ambylcarpa and Shekwasha mandarins (and Volkamer lemon) with selected pummelo material. The first plant regeneration using the widely-adapted C. ambylcarpa as a parent was achieved.

Continuing Field Trials: Planted the first half of a trial of selected diploid pummelo material into a high pH calcareous site infested with Diaprepes (Fort Pierce REC with Ed Stover). Continued data collection from a Murcott trial comparing 31 rootstocks in calcareous soil; best rootstocks so far for yield and soil adaptation are Volk, Smooth Flat Seville, and C. ambylcarpa. Collected yield, fruit quality, and yield efficiency data from two major somatic hybrid rootstocks trials (US Sugar and H. McTeer); best performing somatic hybrid rootstocks include sour orange + Carrizo, Cleopatra + trifoliate orange, sour orange + Palestine sweet lime, sour orange + rangpur, and Cleo + rough lemon. Two field days were held, one showing the somatic hybrid rootstocks at the McTeer trial, and the second showing a large Marsh grapefruit rootstock trial at Hobe Sound (Becker), where a second year of data was collected. A Tahiti lime trial of nearly 1000 trees on 52 rootstocks (including sexual and somatic hybrids) was planted in limerock at Miami to test for tolerance to calcareous soil. Liners of selected sexual and somatic hybrids, and other selections were propagated for an Indian River grapefruit rootstock trial (with Scott Growers), and a navel rootstock trial at Conserv II.

FCPRAC Grant $ 87,000

IFAS Contribution $315,000

(Will be continued in subsequent years as a part of 0110-03I Block Grant).

Progress Report for FY 00-01, Final Year.

Abstract

The greatest impediment to developing genetically improved, superior new citrus varieties has been the lack of simple, yet effective, screening and selection procedures. The development of varieties improved for multiple traits requires screening and selection from large families to identify individuals with multi-trait improvements. By identifying easily-scored molecular markers linked to economically important genes, selection for desired traits can be quickly accomplished indirectly by selecting for the markers.

Florida growers will benefit from this research, because genetically superior varieties will become available much quicker than ever before.

Objectives

The overall goal of this project is to use previously developed markers to screen and select rootstock hybrids with resistance or tolerance to CTV, citrus nematode, cold, and salinity, and to develop new markers for other important genetic traits including resistance to fungal pathogens, and fruit quality characteristics.

Summary of Accomplishments

Substantial progress was made toward the objectives of tagging genes for cold hardiness and those involved in the development of fruit color. Full cDNA sequences of some genes involved in cold acclimation in citrus have been obtained, as well as several of their promoter sequences. All the first genes in the pathway of citrus color formation (phytoene synthase, phytoene desaturase, zeta-carotene desaturase, lycopene cyclase) have been cloned and sequenced. There are clear differences in their expression and, surprisingly, in gene sequence between red and white grapefruit. These results will enable precise tagging of genes, as well as open the possibilities of manipulations for variety improvement. A study of QTLs (quantitative trait loci) controlling morphological development was completed this past year. Additional work on developing inter-simple sequence repeat (ISSR) markers was performed, which now provides a new class of markers useful for gene mapping. High resolution, fine mapping of the CTV resistance gene region, using BAC clone ends, has resulted in the development of new markers that completely cosegregate with the gene, which results in extremely precise determination of susceptibility or resistance. These resistance gene markers, and those developed previously for citrus nematode resistance, have been used to identify rootstock candidates for advanced testing.

FCPRAC Grants $ 49,000z

$ 20,000y

Agency Contribution $ 60,000x

Other Grants $110,000w

zFunds from this granted project, 942-27.

yFunds allocated to Gmitter from FCPRAC Project No. 928-27, indirectly related to 942-27.

xEstimated IFAS contribution based on salaries of PIs, technical support staff, and graduate students; percentage of time allocated to the project; and research support funds. This figure does not include overhead, which is substantially greater than the figure given.

wIdentification and functional analysis of cDNA sequences of the CTV-resistance gene; indirectly related to 942-27.

Investigators: Kim D. Bowman

USHRL - USDA-ARS, Ft. Pierce

Ed Stover

IFAS - UF - IRREC

Bob Rouse

IFAS - UF - SWFREC

Progress Report for FY 00-01, Year 3 of 8.

Abstract

Growers do not make a good profit from trees that die from disease, are slow to begin bearing, produce poor quality fruit, are too large for easy harvest, or never produce good yields. Efficiency of production can be improved and profits increased by planting trees on improved rootstocks. Several new USDA hybrid rootstocks have had outstanding performance in some field locations. Trials with these new hybrid rootstocks have been established in several locations around Florida. This project will focus on collecting complete performance information from existing trials and establishing new rootstock trials at additional sites. The proposed research will help identify superior new rootstocks for commercial use by the Florida industry.

Objectives

Summary of Accomplishments

Excellent progress has been made on evaluation of new rootstock selections in several established trials. During this fiscal year, performance information was collected from trials of new rootstocks in Lake, Polk, Indian River, St. Lucie, Martin, and Collier counties. Performance of rootstocks US-812, US-852, US-897, US-942, and US-802 has continued to be good, and each has appeared to be superior to standard rootstocks for some production situations. The performance of US-812 rootstock has been outstanding in multiple trials and it was officially released by USDA for use in Florida on May 11, 2001. US-897 and US-942 rootstocks appear to combine good fruit quality, yield, and disease resistance with semi-dwarf tree size, and will be considered for release in a couple more years. Several other promising new rootstocks that combine disease resistance with high productivity and broad soil adaptation are also in the pipeline, but at an earlier stage in the evaluation process. Preliminary work with sour orange and related hybrids has been described in presentations for the International Citrus Congress and at the 2001 meeting of the Florida State Horticultural Society. New cooperative field trials have been established in Indian River, St. Lucie, Collier, Lee, and Dade counties during this fiscal year. Several other grower trials and demonstration blocks of new USDA rootstocks were also started in other locations.

FCPRAC Grants $ 32,000

Total $ 462,000

(Will be continued in subsequent years as a part of 0110-03I Block Grant).

J. W. Grosser

W. S. Castle

IFAS - UF - CREC

Progress Report for FY 00-01, Final Year.

Varieties well-adapted to Florida growing conditions are the basis of the citrus industry. However, there are obvious drawbacks with currently grown varieties. Early oranges are of poor quality, with inadequate color. New pigmented grapefruit varieties have been developed to satisfy consumer demand, but their horticultural performance is inadequate. Florida mandarins produce seedy fruit that are unacceptable to the market. New varieties that overcome these drawbacks can provide the basis for new opportunities. Multiple strategies are being followed to achieve the goal of providing growers with the best possible varieties in the future.

Summary of Accomplishments

Embryos were rescued from 13 interploid crosses (2000) for seedless variety development; from these, a total of 765 hybrids were recovered. In 2001, 25 interploid crosses were made, along with 15 crosses for breeding parent improvement. Several new somatic hybrids, from late maturing selections, were created and planted out for future use in crosses. Protoplast fusion experiments, using Satsuma and Ortanique, were conducted to produce potentially seedless cybrids. New somaclone families of Flame and other grapefruit, and

from various early and late oranges, were propagated and planted. Two early Duncan grapefruit selections and 3 mandarin hybrids were irradiated to induce seedlessness. First fruit evaluations from mandarin families provided several interesting selections characterized by large fruit size, EZ peeling, and excellent appearance and eating quality. New field trials of low-seeded Murcotts, LB8-9, and more than 35 selected orange somaclones (including 4 early Valencias, >20 late Valencias, and 10 improved Hamlin clones) were planted. Another season's data were collected from various scion variety trials throughout Florida. Propagation of the newly released early-season oranges has continued. We have provided almost 37,000 Earlygold buds and 5,000 Itaborai buds. New orange selections introduced by seed have been planted in two locations and are expected to produce fruit the next season.

Investigators: M. A. Ritenour

IFAS - UF - IRREC

M. E. Tignor, Jr.

University of Vermont

Progress Report for FY 00-01, Year 2 of 2.

The World Wide Web has been growing exponentially since 1993. However, unless a person is fairly adept at using search engines, it can be arduous or impossible to find specific information. The Florida Citrus Industry will be surveyed initially to determine the types of information they would like to access from a centralized citrus web site. Then a web site will be constructed allowing easy access to that information.

Web Site Address (URL): http://www.fcprac.ifas.ufl.edu or http://flcitrus.ifas.ufl.edu (both access the same site)

A Dell PowerEdge 2300 Server was purchased, installed, and is presently on-line. The site has been organized with main topic areas on the left side of the page and more specific topic areas at the top (depending on the topic chosen). Information can be found following either the topical arrangement, or by using the site search engine. As of August 10, 2001, information on the web site includes:

FCPRAC Grants $2,500

Total $9,370