The objectives of this study are: 1) to develop a series of flexible stochastic models to predict the temporal increase and spatial spread of citrus HLB and canker. They can be used in a number of ways: to predict spread and to analyze the effectiveness of control strategies both in plantations and State-wide. 2) Test various control methods under field conditions to evaluate effects and collect data to parameterize models. SEIDR model. Using Markov-chain Monte Carlo methods, and extensive data from infected areas of South Florida for successive snapshots of the occurrence of symptomatic detected trees in known populations of susceptible trees, we have been able to estimate the transmission rates and dispersal kernel for HLB. We now have a working model that focuses on the differential effects of host age on epidemiological parameters as well as variability across the plantation and that allows for uncertainty in the parameters as well as variability over time and through space. We used Baysian methods to infer posterior densities on the model parameters. The uncertainty is then incorporated in models to predict spread and to allow for uncertainty in the efficiency and comparison of control methods. A front-end (a web based version of the model) was developed for non-researcher users has been nearly finalized and is in validation testing. Both residential and commercial citrus scenarios are being tested and a wide variety of epidemiological and climate/weather variables have been included and are user selectable and changeable via sliding controls. Currently we are examining various disease control/mitigation parameters and are visualizing the effect of these various control strategies. This web tool runs simulations one at a time and is highly instructive to growers and regulators. It is based on a more formal analytical model that can run thousands of simulations based on the same parameters and provide more statistically valid predictions for regulatory intervention strategy building and regulatory/industry decision making. Via this model we have been able to examine the effects of various controls such as using insecticide applications or not, removing infected trees or not, and the effect of HLB infection in young versus older trees. Model output suggests that at least for older trees controlling secondary infections by diseased tree removal and insecticide applications plus controlling primary infection from new insect immigrations by areawide control strategies, can reduce disease increase to a manageable 2 to 5% increase per year, which appears to be economically sustainable. The model continues to be improved upon to capture more and more of the true features of the data and the disease. The model is being extended to estimate spread, should HLB be introduced into new areas such as TX, CA or AZ.
The intent of this study is to examine the effect of windbreaks, copper sprays to reduce infection, and leafminer treatments to determine there individual and combined effects on control of citrus canker in Brazilian commercial citrus and the applicability of this strategy to the US commercial citrus industry. A preliminary study was published in Crop Protection 27:807-813, that indicated that copper and insecticide applications significantly reduced canker infection but windbreaks did not have any effect. It is believed this is the case because the windbreaks were not tall enough. Thus a new series of plots with much more extensive windbreaks were established. This was accomplished via a USDA/ARS specific cooperative agreement with the University of Sao Paulo, and the Brazilian cooperator, funds were transferred for collaboration, plot maintainence and experimental conduct. Permission was obtained to use an IAPAR farm, in Xambr’, Parana state, located 350 km west from Londrina and 250 km west from Maring’ where replicated field plots were established. The cultivar used is P’ra on Rangpur lime, two years of age at the beginning of the experiment. Windbreaks were completed and plants were be established in Mid April 2010, but severe winds damaged the initial windbreaks which have now been rebuilt. The following treatments are being applied: 1) no sprays (control), 2) Cu++ sprays to reduce citrus canker incidence, and 3) insecticide sprays to inhibit infestations of Asian leafminer (secondary effects). Main effects are windbreak versus no windbreaks. Citrus canker incidence is being estimated on multiple branches on each tree treated as the number of leaves per branch infected. Data collection is underway and continuing. We anticipate running these plots for 2-3 more years to collect all necessary data. The development of the Programmable leaf wetness controller (PLWC) software was written, debugged, is complete, and the control program is working well. New leaf wetness sensors were designed and constructed and calibrated. An electronic glitch was determined in the leaf wetness sensors and an new control circuitry was designed and constructed to overcome. The new design is currently under examination. Publications: 167. Bock, C. H., Graham, J. H., Gottwald, T. R., Cook, A. Z., and Parker, P. E. 2010. Wind speed effects on the quantity of Xanthomonas citri subsp. citri dispersed downwind from canopies of grapefruit tree infected with citrus canker. Plant Di Bock C.H., Graham, J.H., Gottwald, T.R., Cook, A.Z., and Parker, P.E. 2010. Wind speed and wind-associated leaf injury affect severity of citrus canker on Swingle citrumelo. Eur J. Plant Path 128:21-38 Bock, CH, Parker, PE, Cook, AZ, Graham, JH and Gottwald, TR. 2001. Infection and decontamination of citrus canker and inoculated the surfaces. Crop Protection 30:259-264. Hall, D.G., Gottwald, T.R. and C.H. Bock. 2010. Exacerbation of citrus canker by citrus leafminer Phyllocnistis citrella in Florida. Florida Entomologist. Florida Entomologist 93:558-566. Bock, C.H., Gottwald, T.R. and Parker, P.E. 2011. Distribution of canker lesions on the surface of diseased grapefruit. Plant Pathology (Accepted).
This project has 5 objectives: (1) evaluate efficiency of ACP control techniques in cooperation with growers, (2) develop efficient monitoring methods for ACP, (3) accelerate testing of new chemistries and techniques for ACP management, (4) evaluate the economic component of the comprehensive program, and (5) provide an information bridge between researchers, growers, and industry. Dr. Moneen Jones joined the project 3 Jan 11 after the departure of Dr. Alejandro Arevalo. In the course of meetings with the Gulf Citrus Growers Association board of directors, it was agreed that the ‘Gulf CHMA’ would no longer include northeastern Glades Co where growers are working with Highlands Co growers, nor Charlotte Co where groves occur in a contiguous area that would work more efficiently as an independent CHMA. Coordinated sprays: 39071 acres Nov-Dec and 35,140 Jan-Feb for a total of 74,211 by air. LV ground equipment was used instead of fixed wing aircraft by so total acreage and frequency sprayed is as much or more than the previous two dormant seasons. Psyllid counts made by DPI-CHRP in commercial blocks went from 9.1 per 100 taps in Nov to 2.3 in Apr (N = 76 and 69 respectively). The following field and laboratory experiments have commenced. (1) A 10.9 acre trial to determine the efficacy of low volume application of 435 horticulture mineral oil sprayed at two-week intervals compared to a grower standard and untreated check. Baseline yield and PCR samples have been taken and 3 sprays applied (2 Mar, 22 Mar, 8 Apr). The grower has applied 3 qts of Carbaryl 4L + 1gal HMO (22 Mar) and 6 oz/ac of Azasol (8 Apr), both with Surround WP as a coverage applicator. Thus far, mean psyllid populations have been below the 0.2 threshold in all treatments (0.07 +/- 0.03SEM oil, 0.05 +/- 0.03SEM grower standard, 0.1 +/- SEM control), with no significant differences between treatments. Baseline total yield and quality data was obtained. (2) Evaluation of dose-response relationships of ACP adults to two insecticides: commercial grade thiamethoxam (Actara 25WG) and lambda cyhalothrin (Warrior) and a pre-mix (Endigo ZC) of the same. Psyllid colonies in replicated cages will be subjected to increasing rates of either of the two products in rotation or the premix and the rate of selection for resistance evaluated. This information is crucial for resistance management of psyllids. (3) Grower concern is mounting over increased Incidence and intensity of citrus leafminer (CLM) damage, presumably in response to psyllid sprays. We have initiated 2 field trials using pheromone traps to better evaluate and target CLM populations, particularly early season generations. Pheromone traps were placed in groves on 18 Feb, and the 1st sustained flight observed on 22 Feb with peak flight observed on 0 Mar, after 156 degree days (dd) had elapsed. The second peak flight occurred at 421 dd suggesting an approximate generation time of 265 dd. Early sprays of Intrepid 2F were applied on 24 Feb (Duda Grove, Orange Hammock), and 14 Mar (Felda Grove) according to flush presence or 1st peak moth flight respectively. The grower at Duda sprayed 16oz/ac of Movento 240SC on previously untreated plots 11 Apr. Injury to the 4 major flushes will be evaluated using a Horsefall Barret system. Thus far, CLM damage has been minimal. Second marking of flush and density determination will begin this month.
Ultra low-volume and Aerial Application of Insecticides and Horticultural Mineral to Control Asian Citrus Psyllid in Commercial Orchards. Low volume (LV) aerial and ground sprays have become an important method of application during the dormant season and at other times in SW Florida. We continue our evaluations of LV application of 435 horticultural mineral oil (HMO) which has shown promising results the last 3 years. We began a fifth trial on February 2011 in a 10.9 acre plot of ‘Valencia’ orange in Lee County to compare the efficacy of low volume spray spray of 435 horticultural spray oil (HMO) with the grower standard and an untreated control. The grower is applying a foliar nutritional program throughout the block. The 3 treatments are set out in 3×3 Latin square design (3 replications). We are using a Proptec rotary atomizer P400D spray machine for all treatments. HMO is applied alone (no water) every 2 weeks at 2 gpa. Three sprays of 435 oil (3/2/11, 3/22/11, 4/8/11) have been completed thus far. A standard is applied whenever the grower sprays the rest of the block. A grower standard of 3 qt Carbaryl 4L plus 1 gallon HMO/ac was applied in 10 gpa spray mix on 22 Mar. Surround WP (kaolin clay) at 0.5 lb/ac was included as a coverage indicator. On 8 April, 6-oz/ac of Azasol, 2-gal./ac oil, and Surround (marker) was applied in a 10-gal mix. Thus far the mean psyllid counts have been below the 0.2 adults/stem tap sample threshold in all treatments (0.03 +/- 0.01SEM oil, 0.04 +/- 0.01SEM grower standard, 0.03 +/-SEM control) with no significant differences among treatments (3/16/11, 3/30/11). Due to the repeated incidence of frost in late winter and resulting high fruit drop, harvest of the Valencias was done much earlier in the season (2/6/11) than normal (April). Samples sent to the CREC Fruit Quality Laboratory indicated that juice content was on average less than 50% (0.41). Although the total brix was within normal range of 9 – 14 for all samples, the acid content was below the normal (1.0 – 0.5) in 5 of 8 samples tested. There was no significant treatment effect on yield, but highest production was seen from trees treated with the grower standard with 12.6 lbs fruit/tree followed by HMO (10.5) and control (6.1). An experiment initiated in February compared low (5 or 10 GPA using Proptec) vs. high (40 or 120 GPA using Airblast) volume applications of Movento 240 SC (16 oz/ac) along with Mustang Max 1.5 EC (4 oz/ac in 5 GPA using Proptec), Baythroid XL 1 EC (3 oz/ac in 5 GPA using Proptec) and Provado 1.6 F + Agrimek 0.15 EC (3.5 oz/ac + 10 oz/ac in 120 GPA using Airblast). This is a repeat of an experiment run last year this time. Once again we are seeing as good or better results from the low volume applications of Movento plus oil using the Proptec as from the high volume applicaitons using conventional air blast technology. All treatments provided significant reduction in psyllid adults through 5 weeks after treatment and nymphs through 4 weeks except Mustang Max, low rate of Movento using Proptec, and Provado + Agrimek against nymphs at the last observation.
Spatial and Temporal Incidence of Ca. Liberibacter in Citrus and Psyllids Detected Using Real Time PCR, April 2011. In 2010, psyllid adults from our HLB negative colony on orange jasmine were caged on new shoots (10-12 adults/shoot/ per tree) that had been caged immediately after trimming and were not exposed to feral psyllid population. On the same tree an additional cage was placed on a previously uncaged shoot that was infested with feral psyllid nymphs. These adults and nymphs remained caged on the shoots for three weeks. Some adults from laboratory reproduced in the cages so when collected there were some nymphs available. Similarly cages with feral populations also had some nymphs and adults at the time of collection. Using PCR, 40 shoots tested HLB negative with average Ct value of 39.8 ‘ 0.07 and 15 shoots tested HLB positive with average Ct value of 27.4 ‘ 0.7. From lab reared adults caged on HLB negative shoots 69 were tested and all were negative. From their nymphal progeny 58 were tested and 1.7% were positive with Ct value 29.8. From the ones caged on HLB positive shoots 51 adults were tested and 12% were positive with average Ct value of 29.6 ‘ 0.7. Among 31 nymphs none were positive. Out of 88 adults that emerged from feral nymphs caged on HLB negative shoots 10% were positive with average Ct value of 28.9 ‘ 0.9. Only 5 nymphs were tested and all were negative. Among 53 adults that developed from feral nymphs caged on HLB positive shoots 9% were positive with average Ct value of 29.6 ‘ 0.9. No nymphs were tested. These colonies were re-treated on April 8, 2011 and titer values and CT values are being calculated to correlate with data from 2010. We are also evaluating the effect of vector management on bacterial titer and fruit yield in the same 12-acre block of a commercial orange grove. The block was divided into 16 plots organized in a randomized block design with eight replicates and four treatments: (1) Nutritional (2) Insecticides (3) Insecticides + Nutritionals and (4) Untreated. Treatments (1) and (4) remained free of insecticides and the vector was allowed to thrive. In treatments (3) and (4), the psyllid population was monitored every 2 weeks and insecticide was sprayed when insect populations surpassed the nominal threshold of 0.5 psyllids per tap sample. To assess the titer values, we selected symptomatic branches on every fifth tree in every row for real-time PCR analysis every four months. Initially CT values and the percentage of PCR positive trees did not differ between treatments. In the last two years, CT values have dropped and most trees eventually tested positive. Treated trees had significantly higher yields than the untreated trees. These results indicate that mitigation of vector pressure with insecticide decreased alleviated bacterial titer over time and positively affected yield despite the same incidence of HLB. In these trials, total of 176 psyllids (adult and nymphs) were processed on 6/19/09 sampling, 91 psyllids (adult and nymphs) 6/26/09, 149 psyllids (adult and nymphs) from B9, Silver Strand 2/8/10 sampling, 384 psyllids on 8/2/10, and 1200 since February 2011. Data are being entered into a psyllid computer data base that has been specifically designed to analyze this information and correlate treatment, psyllid CT value, and tree CT value. Another protocol that was established in 2010 was the quantification of the HLB bacteria in both the psyllid and host tissue using a standardize curve. The objectives of this grant are ahead of schedule since grant was initiated prior to release of grant funds the first year, therefore we have three years data as of this harvest.
Mr. Brandon Page was recently hired to serve as the CHMA program assistant within IFAS. Mr. Page is housed at the CREC and since his hiring a couple of weeks ago, has attended CHMA grower meetings, interacted with citrus agents at their meetings, and begun work to get the CHMA website up to date. Mr. Page has been contacting CHMA grower leaders to help facilitate their communication of ongoing psyllid control efforts through the CHMA website and through email listservs Mr. Page has setup. He has also been working to summarize data from previous and current psyllid scouting reports in a grower friendly format. In the coming months, this information will be delivered to growers in a timely manner via the website and at grower meetings. Should his assistance be needed, Mr. Page can be contacted at the CREC at 863-956-8653 (bpage@ufl.edu).
Resulting from the freeze on December 15 and two other freeze mornings in January we suffered leaf drop and ice in fruit in our foliar applied nutrition trials at Immokalee. We experienced temperatures of 25 degrees F for several hours resulting in leaf and fruit drop, and some terminal twig damage. The spring growth was good and the trees have rebounded with thick canopies, flowered and set fruit. We are completing the second year of this funded project and the third year of data collection from our experiments with the Boyd cocktail of foliar applied nutrients, phosphite, and SARs. treatments receiving the macro- and micro nutrients nutrients along with phosphite continue to produce the most yield. trials are being harvested and fruit yield will be reported in the next report. Data from the root study showed root density had increased in all treatments from 2009 to 2010 on trees where foliar nutrition was applied. Overall, root density had increased from 1.016 to 1.579 cm root/cm3 soil at depth of 0-6 inches and from 0.734 to 1.081 at a depth of 6-12 inches in flatwoods soils. Orientation of where the soil samples were taken around the tree as north, east, south, and west was not significant. Preliminary results from work with Dr. Brlansky looking at the phloem indicates open phloem sieve tubes where our foliar nutritional is being applied, and blocked phloem from samples from our untreated controls. The rehabilitation trial of 15 year-old HLB Valencia trees mechanically buckhorned in spring 2010 have shown tremendous regrowth. Compared to unpruned trees receiving the same foliage nutritional treatments, the pruned trees had twice the shoot growth in March, three times the shoot length in May, and 1.5 times the summer growth. Last week we harvested the 30 acre ‘Vlaencia’ block in a commercial with treatments of all the componet parts of the Boyd cocktail. The data is being entered in the computer for analysis and will be reported in the next quarterly report. We have completed the third year of a replicated experiment in a 12-acre experiment commercial block of 8-year-old ‘Valencia’ oranges on ‘Swingle’ to test effects of micro-nutrients + systemic acquired resistance inducers, and Asian citrus psyllid (ACP) chemical control on ACP populations on Can. Libericacter asiaticus (CLas) titer, and plant yield. Since our last report we have applied two dormant sprays on the treated plots: one application Imidan 70W at 1lb formulated material/acre in 100gal/acre on 23Nov10, and onve of Danitol 2.4EC at a rate of 12oz/acre on 1Jan11. Psyllid populations in the insecticide and insecticide+nutritional plots were zero until 25Feb11 scouting, when suddenly increased to more than 0.4 psyllids per tap sample, although psyllids on both were significantly less than the nutritional and control (P < 0.02) and 0.001, respectively). Following another spray of Danitol 2.4EC @ 12 oz/ac on 11, psyllid counts in treated blocks were reduced to 0.03/tap. In January, we collected plant samples for HLB detection, and these are still in process. We will again collect samples for HLB analysis this month. The third harvest was completed last week (4/5/11). This harvest is considered to be key to confirm the observed tendencies from years past. Once again, the best treatment was nutrition+insecticide with 101 lb/tree compared to 92, 71 and 56 lbs for the insecticide only, untreated and nutritional only treatments respectively. Main components analysis indicated again that only the insecticide factor was significant (P <0.003). Fruit samples will be sent to the CREC fruit quality laboratory for analysis of lbs. juice per box, acid, total brix, and ratio.
This program began in June 1, 2009 and ended in February 28, 2011. The goal of the program was to establish a monitoring program for Asian Citrus Psyllid to document an area wide spray psyllid suppression program. Participating agencies were: Douglas Bournique, Principal Investigator, Indian River Citrus League; Michael Rogers, PhD, UF, IFAS Lake Alfred; David Hall, PhD, USDA/ARS Ft. Pierce; Herbert N. Nigg, PhD, Professor Emeritus, UF; Calie Jenkins, FDACS; Jim Carter and Rusty Noah, FDACS, DPI, and Linda Minton, Southeastern Aerial Crop Service, Fort Pierce, Florida. The logistics of this program were as follows. An overall psyllid monitoring program for Indian River, St. Lucie and Martin counties fed data to Dr. Hall at USDA, Ft. Pierce. Data were correlated with the tracking system for area wide pesticide aerial applications through Southeastern Aerial Crop Service. Caribbean Fruit Fly monitoring was conducted in sync with aerial applications to determine if control of psyllid resulted in control of Caribbean Fruit Fly. Dr. Hall analyzed the psyllid data weekly and produced graphs and figures describing the results. The program was established with malathion based upon data provided by Dr. Rogers, UF. Mustang was added based upon psyllid data provided by Dr. Rogers and upon fly data provided by Dr. Nigg and Calie Jenkins. Asian Citrus psyllid was monitored from 6/1/2009 through 2/28/2011 in St. Lucie, Martin and Indian River counties. During the 21 month program 224,190 trees were monitored for psyllid; 29,449 psyllids were counted during this period. From June 2009 through May 2010 abandoned, fresh and juice groves were compared. Caribbean fruit fly was monitored with 400 McPhail traps distributed across a 45-square mile area within the spray program in Vero Beach/Indian River County, north and south of Highway 60 and west of I-95 (St. John’s Marsh area). Varieties included White Marsh, Pink Marsh, Star Ruby and Flame grapefruit and Navel, Hamlin, Valencia, Murcott and Temple oranges. Bait sprays were applied to maintain fly-free certification for export. Psyllid levels were higher in abandoned groves compared to commercial groves. The southeast corner of a block had the most psyllids; the center of a block had the lowest. Psyllids were widespread, but hotspots were common. Due to widespread and effective grower control of psyllid, this monitoring program provided little evidence that the area wide spray program was effective. Psyllid sprays in September 2010 and February 2011 were successful in specific blocks but overall area wide monitoring did not confirm this suppression. Data indicated that an area wide psyllid program also suppressed Caribbean Fruit Fly for the certification program. Grower participation and weather were unanticipated problems in the area wide program. This program established a monitoring program for psyllid populations that continues in 2011 through USDA and FDACS funding with regular reports from Dr. Hall, USDA. Through judicious use of funds, this project returned $20,188 to the Florida citrus growers for other programs.
We are attempting to develop RNAi-based strategies and reagents for the tomato/potato psyllid (Bactericerca cockerelli). We envision applications of our effort as a complementary means for controlling the Asian citrus psyllid, Diaphorina citri. Our hope is that by inducing effective RNAi in recipient psyllids, we can help to control psyllid-vectored plant pathogens with the ultimate target being Ca. Liberibacter asiaticus, the causal agent of citrus greening. We have cloned hundreds of B. cockerelli sequences and developed an artificial feeding system for their delivery and evaluation for RNAi effects in psyllids. Using this system, we screened the homologues of actin, ATPase, Hsp70 and CLIC for RNA interference effects against B. cockerelli. We found increased mortality of dsRNA-fed psyllids and the specific down-regulation of target gene expression. We also constructed an artificial chimeric sequence for actin, ATPase, Hsp70 and CLIC. Oral feeding of dsRNAs for this chimera sequence resulted in significantly higher mortality compared with the dsRNA of any of the individual sequence, demonstrating possible synergistic effects of these sequences on psyllid survival. Interestingly, combination of separately-synthesized dsRNA for these sequences did not increase psyllid mortality. The possible explanation is that some favorable sequence structures featured in the chimera sequence is missing in the combined dsRNAs. This is encouraging, and we will apply this sequence for in vivo expression system to test the efficiency for RNAi effects. Within a given mRNA transcript, the potency of different regions of the transcript sequences can be differentially susceptible for RNAi effects. There is accumulating evidence that the 3′-region of a mRNA is a better RNAi target than is the 5′-region. Based on this possibility, we have attempted to clone the full-length cDNAs for several selected psyllid target RNAs. We have cloned the complete coding sequence of the actin gene, and four dsRNA corresponding to different regions were synthesized and are under evaluation for qualitative and quantitative effects via artificial feeding experiments. The same approach is being used for additional psyllid genes. We are also attempting to develop means for more rapid evaluation of RNAi effects in plants by using plant virus-based expression systems. We have used a Tobacco mosaic virus (TMV)-based plant expression system to express B. cockerelli sequences in plants. However, TMV systemic expression of insert sequences requires approximately 3-4 weeks and resulting infections are non-uniform within tomatoes. We have now evaluated different virus vectors and host plants, including TMV, Tobacco rattle virus (TRV) and Potato virus X (PVX) in different host species such as tomatoes, tobacco, datura, tomatillo and Nicotiana clevelandii, all of which are good host plants for B. cockerelli. TMV systemic infections in tomatillo develop very rapidly, within one week and the tomato psyllid readily feeds on tomatillo. TRV and PVX both also offer opportunities in other plant species. The combination of viruses and plants will allow us to rapidly test RNAi activities in plants.
This project includes experiments being conducted by USDA-ARS and University of Florida on protecting newly planted citrus trees from Asian citrus psyllid and huanglongbing. This progress report reviews one experiment being conducted by USDA-ARS in east-central Florida. Three potential psyllid management programs are being investigated for protecting a new planting of citrus: (1) citrus subjected to an intensive insecticide program (8 treatments per year on a calendar schedule, annual chemical cost of $198/acre); (2) citrus interplanted with jasmine, with citrus subjected to a moderate insecticide program (4 treatments per year on a calendar schedule, annual chemical cost of $156/acre) and jasmine not treated with insecticides; and (3) citrus interplanted with jasmine, with citrus subjected to a moderate insecticide program (4 treatments per year on a calendar schedule, annual chemical cost of $156/acre) and jasmine regularly treated with insecticides (six applications of imidacloprid per year, annual chemical cost of $56/acre) (for treatment 3, a total annual chemical cost of $213/acre). The experiment was in the midst of high psyllid pressure and HLB inoculum. Numbers of psyllids captured on sticky traps indicated that relatively good psyllid control was achieved under the intensive insecticide program ‘ over all sample periods, there was a mean (SEM) number of 0.4 (0.1) psyllids per trap. Under the reduced insecticide program for citrus interplanted with jasmine, relatively poor control of psyllids was achieved in citrus when jasmine was treated with insecticides [1.4 (0.4) psyllids per trap] and even poorer control was achieved in in citrus with jasmine not treated with pesticide [4.7 (0.2) psyllids per trap]. Over all sample periods, psyllids were most abundant in jasmine not treated with insecticides [12.3 (2.9) adults per trap] and moderately abundant in jasmine treated with insecticides [2.4 (0.7) adults per trap]. Lady beetles were relatively abundant in jasmine plants whether jasmine was treated [0.11 (0.03) beetles per trap] or not treated with pesticide [0.13 (0.03) beetles per trap]. Compared to numbers of beetles trapped in jasmine, numbers trapped in citrus were similar ‘ 0.08 (0.02) per trap under treatment 1; 0.16 (0.04) per trap under treatment 2; and 0.11 (0.02) per trap under treatment 3. Although less than 1% of the trees under each treatment tested positive for HLB 12 months after planting, by August 2010 (27 months after planting), the percentage of trees infected by HLB under treatments 1, 2 and 3 averaged 28, 35, and 30%, respectively. There have been no significant differences among the three treatments in percentages of trees infected on any sample date. By February 2011 and across all three treatments, an average of 45.9% of the trees in each plot had become infected and removed. Based on these results, planting new citrus trees and getting them to a producing stage is difficult if HLB is endemic in the area surrounding the new planting and psyllids are not controlled area-wide. Under the circumstances of this small plot experiment, the incidence and spread of HLB have not been reduced under an intensive insecticide program consisting of eight calendar-based sprays annually. It remained possible that a reduction in the incidence and spread of HLB might have been seen in citrus planted with jasmine under either treatment 2 or 3 had these plants been larger in size when the citrus was planted. Also, basing psyllid sprays on scouting data may be superior to basing them on calendar dates, although more than eight sprays might have been needed.
This project started in May 2010 with the objective of evaluating impact of psyllid control programs on non target pests and beneficial insects. During first year we conducted six separate replicated experiments at SWFREC to evaluate impact of recommended and experimental insecticides using 54 treatments on psyllids, leafminers, ladybeetles, spiders, ants and lacewings in 15 yr old trees of ‘Valencia’ oranges. Highlights were reported in the quarterly reports. Two more replicated trials were initiated on oranges in commercial groves in Hendry county, one in a 35 acre block of ‘Early Gold’ and the other in a 16 acre block of ‘Valencia’. These experiments include 4 treatments: three spray programs for psyllid one receiving monthly calendar sprays, two intended to maintain ACP populations below thresholds of 0.2 or 0.7 psyllids per tap sample and an untreated check. Stem tap sampling, vacuum sampling, sticky traps and shoot examination are being used to monitor populations of psyllids and non target pests and beneficial insects. We are also ready to use exclusion techniques to evaluate pest mortality from predaceous and parasitic arthropods under different psyllid control programs and evaluate the relationship with intensity of insecticide use. About 100 cages to restrict predators and parasitoids from reaching the pests colonies on citrus trees were fabricated to make comparisons with unprotected colonies. We have also identified additional commercial groves to monitor populations of Florida red scale, lesser snow scale, and blackflies and whiteflies. Results from this year studies were presented at local and regional meetings and we are working on publications for Arthropod Management Tests, Proceedings of the Florida Horticultural Society, and peer reviewed journals. In addition to measuring the effects of insecticide use on psyllids and non targets we also surveyed grove managers in southwest FL on their insecticide use and incidence of non target pests. Thirty percent reported 6-11 sprays of insecticides to control psyllids during the past 12 months and 100%, 67%, and 33% of them reported seeing an increase in the populations of citrus leafminer, scales and mites, respectively. In contrast, 70% reported 5 or less sprays and only 14% and 29% of those reported increased citrus leafminer and mites, respectively. We also compared organic and conventional groves and found huge differences in the populations of ants and spiders between the two practices. An average of 22 ants and 11 spiders were observed per 140 tap samples conducted in the organic grove compared to 0.3 ants and 4 spiders observed in the conventional grove. Leafminer damage indicated a very serious infestation in the conventional grove compared to the organic grove, suggesting that increased insecticide use can lead to reduced populations of important natural enemies and increase in non target pests. P. A. Stansly, J. A. Qureshi and B. C. Kostyk. 2010. Efficacy of foliar applications of insecticides for control of Asian citrus psyllid and citrus leafminer in oranges during spring. Arthropod Management Tests (In press) P. A. Stansly, J. A. Qureshi and B. C. Kostyk. 2010. Foliar applications of BYI02960 compared to some commonly used insecticides for control of Asian citrus psyllid and citrus leafminer in oranges: summer. Arthropod Management Tests (In press) P. A. Stansly, J. A. Qureshi and B. C. Kostyk. 2010. Effect of spray volume and sprayer type on efficacy of insecticides for control of Asian citrus psyllid and citrus leafminer on oranges. Arthropod Management Tests (In press)
The goal of the present project is to establish economic thresholds under different juice price scenarios that optimize returns on investment when a nutrient/SAR package is being applied in groves with moderate to high incidence of HLB. Two 3-year field experiments were initiated in two commercial orange blocks in Hendry County (southwest Florida). One of the groves is planted with ‘Earlygold’ oranges and the other with ‘Valencia’ oranges. Average HLB incidence estimated in both groves based on PCR analysis of a random sample of 160 trees is 98% in ‘Earlygold’ and 76% in ‘Valencia’. Experimental design is randomized complete block with 4 replicates and 4 treatments: (1) No insecticide, (2) Calendar applications, in order to drive vector populations close to 0, (3) nominal threshold of 0.2 psyllids per tap, and (4) nominal threshold of 0.7 psyllids per tap. Calendar applications will be applied approximately every 1-2 months and consist of a rotation of insecticides recommended for managing this pest. Adult psyllid populations are being monitored every two weeks by tap sampling. Flushing patterns and flush infestation are being estimated by assessing the number of new shoots per tree and evaluating the proportion infested with psyllids. Effects of treatments on natural enemy populations is being evaluated by counting beneficials in tap samples, suction samples and flush observations. Treatments (2), (3) and (4) received the dormant spray on January 20 in the ”Early Gold’ block and on January 21 in the “Valencia” block. Both blocks were sprayed with fenpropathrin (Danitol 2.4 EC) at 8 fl oz/ac. Treatment (2) received an additional spray in both blocks on March 16 using the IGR diflubenzuron (Micromite 80WGS) at 6.25 oz/ac. ACP numbers at the present, in all the treatments of the ‘Early Gold’ block are below the nominal thresholds established (0.01 ‘ 0.01, 0.03 ‘ 0.01, 0.02 ‘ 0.01 and 0.05 ‘ 0.02 ACP adults/tap in treatments (1), (2), (3) and (4) respectively). Greatest cumulative ACP values since the beginning of the experiment are being found in treatments (1) and (4) with significantly higher numbers than in treatment (4) (P = 0.0062; df = 3,15; F = 6.03). In the ‘Valencia’ block, ACP populations are increasing in treatments that have not yet been sprayed (0.53 ‘ 0.14 in treatment (1) and 0.23 ‘ 0.06 in treatment (4) at the beginning of April). Density of ACP adults remains close to zero in treatments (2) and (3). Despite of this, no statistical differences are being found yet in the cumulative ACP numbers between treatments (P = 0.9531; df = 3,15; F = 0.11). Block 1 and 2 were harvested on December 2010 and January 2011 respectively. As yet no significant treatment effect on yield has been observed (P = 0.3582; df = 3,15; F = 1.11 for the ‘Earlygold’ block and P = 0.7033; df = 3,15; F = 0.478 for the ‘Valencia’ block). Neither is the correlation between the yield loss and adult ACP cumulative numbers significant (r2 = 0.0026; P = 0.8516; df = 1,14; F = 0.03632 for the ‘Early Gold’ block and r2 = 0.1390; P = 0.1549; df = 1,14; F = 2,261). There were no significant differences among treatments in juice quality measured as the ratio Brix/acid and the Lbs of Solids per box. Predatory flies, spiders, parasitoids and arboreal ants are the beneficial groups that are being found in highest numbers. Calendar applications seem to be negatively affecting mainly spiders and arboreal ants. Further results will be needed to confirm this tendency.
In this project we are working on 1) refinement of sampling methods, 2) testing the influence of adult density and shoot infestation on precision of estimated means and distribution of population within blocks, and 3) evaluation of methods for assessing psyllid density, shoot density, and infestation rates and their integration into a user friendly system accessible to consultants and managers. Progress for the second year is summarized for each objective. 1) Comparisons of the stem tap sampling, sticky traps and sweep nets on data collected in the commercial groves showed that although all methods detect adult psyllids, the stem tap method is rapid, works under either dry or wet conditions, and has proven to be reliable and consistent. A little more than 100 tap samples would be necessary to detect with confidence 15 psyllids with 75% precision, a reasonable threshold during the growing season when trees are producing new growth. Reliance on sticky traps would cause delay in making management decisions and allowing psyllids more time to reproduce and acquire or transmit causal pathogen of HLB. Sweep nets collect a lot of trash and incurs a risk of canker spread. An extension document (EDIS, ENY857/IN867) describing these methods and monitoring protocols for psyllids is in press. We are now comparing stem tap and vacuum sampling in commercial groves. The vacuum sampler is made from a leaf blower and has collected many psyllids where other methods fail because of low populations. 2) A peer review publication using regression and bootstrapping procedures to analyze data collected on comparisons of different sampling methods in commercial groves over a two year period is being prepared. We are using precision levels of 0.25 and 0.01 SEM:mean in order to determine the number of samples required using these methods for routine monitoring and analytical modeling respectively. 3) Detailed description of why, when, and how to monitor psyllids is provided at our website: swfrec.ifas.ufl.edu/entlab. Sampling sheets to conduct tap sampling and record data are available for download. Scouting workshops conducted in collaboration with Hendry county extension were attended by about 100 participants in February 2010 and 2011 before the start of the season to provide training in monitoring psyllids and other pests of citrus. This year training was recorded for posting on the Protect US, Community Invasive Species Network. A field demonstration of tap sampling method was part of the video. So far, more than 500 participants were trained through presentations and workshops on psyllid sampling and management. A survey of grove managers conducted by IFAS extension and SWFREC showed that to make management decisions 75% of SW Florida growers use tap sampling and 63% monitor psyllids more than 12 times a year. Scouts of Division of Plant Industry CHRP have also been trained to monitor psyllids using methods that we developed. They are using our methods to sample for psyllids in order to determine the effectiveness of area wide dormant sprays. The tap method has also been adopted by APHIS to monitor groves throughout the state in support of CHMA programs. Arevalo, A., J. Qureshi and P. Stansly. 2011. Sampling Asian citrus psyllid (ACP) in Florida citrus groves. EDIS (In press) Stansly, P., A. Arevalo and J. Qureshi. 2010. Monitoring methods for Asian citrus psyllid. Citrus Industry 91(4) 20-22.
Objectives were to: (1) import, release and evaluate new strains and species of parasitoid specific to D. citri. (2) identify genetic markers that can be used to track T. radiata in the environment, (3) develop efficient methods for mass rearing and release of T. radiata and possibly other species to increase biological control through augmentation of natural populations, and (4) transfer technology to industry clientele. A summary of accomplishments to date is given below. Objectives 1 and 3: Following initial evaluations in Florida citrus (Ref 1,2) we recommended augmentation of T. radiata to reduce psyllid populations. We brought in new strains from Vietnam, China, and Pakistan (Ref 3,5) established colonies at DPI- Gainesville as well as of the Florida strain originally brought in from Taiwan and South Vietnam both at DPI and SWFREC. So far, more than 250,000 parasitoids have been released and parasitism rates of 60% or more were observed during growing season at released sites compared to < 20% at non release sites or sites sampled in 2006-7. We also showed that parasitoid releases can be integrated with sprays of horticultural oils and nutritionals to reduce insecticide use during growing season to enhance biological control and reduce risk of pest resistance to insecticides. A Diaphorencyrtus aligarhensis colony from Pakistan was established at DPI ,Gainesville, and D. aligarhensis from China colony released with 6-19% parasitism observed in M. paniculata. We collaborated with the California Department of Food and Agriculture, USDA-ARS, USDA-APHIS, Orange Co. and FDACS-DPI to arrange and conduct a Tamaraxia rearing improvement Workshop in Florida, attended by researchers from Fl. TX. CA. Mexico, Costa Rica and Belize. Orange Co. started their production of T. radiata in 2010 and the DPI-Dundee is expected to come on line this year. Objective 2: A collaborative study with molecular biologist, USDA-ARS Mission TX using genetic markers to identify T. radiata from our colonies, Florida and Caribbean was published (Ref 3) and work aimed at identifying genetic origins of parasitoids recovered from field is in progress. A collaborative study on the searching behavior of T. radiata was also published (Ref 4). Objective 4: An extension document (Ref 5) on T. radiata was published at the Cornell Univeristy website "A Guide to Natural Enemies in North America" in addition to several talks given to clientele at local and regional meetings. References: (1) Qureshi, J. A., M. E. Rogers, D. G. Hall, and P. A. Stansly. 2009. Incidence of invasive Diaphorina citri (Hemiptera: Psyllidae) and its introduced parasitoid Tamarixia radiata (Hymenoptera: Eulophidae) in Florida citrus. Journal of Economic Entomology. 102: 247-256. (2) Qureshi, J.A., and Stansly P.A. 2009. Exclusion techniques reveal significant biotic mortality suffered by Asian citrus psyllid Diaphorina citri (Hemiptera: Psyllidae) populations in Florida citrus. Biological Control 50: 129'136. (3) Barr, N.B., D.G. Hall, A. Weathersbee, R. Nguyen, P. A. Stansly, J. A. Qureshi, and D. Flores. 2009. Comparison of laboratory colonies and field populations of Tamarixia radiata, an ecto-parasitoid of the Asian Citrus Psyllid, using ITS and COI DNA sequences. J. Econ Entomol. 102: 2325-2332. (4) Mann, R.S., J. A. Qureshi, P. A. Stansly and L.L. Stelinski. 2010. Behavioral responses of Tamarixia radiata (Hymenoptera: Eulophidae) to volatiles emanating from Diaphorina citri Kuwayama (Hemiptera: Psyllidae) and citrus. Journal of Insect Behavior. 23: 447-458. (5) Qureshi, J. A., and P. A. Stansly. 2010. Tamarixia radiata Waterston [Hymenoptera: Eulophidae], an ectoparasitoid of Diaphorina citri Kuwayama [Hemiptera: Psyllidae]: http://www.nysaes.cornell.edu/ent/biocontrol/parasitoids/Tamarixia.html
The objectives of the 3-year projects were: 1) Developing a system for screening antimicrobial molecules against Las bacteria; 2) Screening and evaluating anti-microbial molecules for suppression of Las bacteria. The major accomplishments are summarized as follows: 1. Development of two screening systems (1) Regeneration system of Las-infected periwinkle cuttings: An optimized system using Las-infected periwinkle cuttings was developed to screen chemical compounds effective for controlling the bacterial population while simultaneously assessing their phytotoxicity. The optimal regeneration conditions were determined to be the use of vermiculite as a growth medium for the cuttings, and a fertilization routine using half-strength Murashige and Tucker medium supplemented with both naphthalene acetic acid (4 .g/ml) and indole-3- butyric acid (4 .g/ml). This system allowed a plant regeneration rate of 60.6% for Las-infected cuttings in contrast to the <1% regeneration rate with water alone. (2) Grafting system of HLB-affected citrus scions: The HLB-affected scions from different phenotypic types (yellow shoot and Blotchy mottle) and different cultivars (lemon and grape fruit) were grafted onto Las-free citrus rootstocks (sour orange and grapefruit). The results showed that more than 60% of HLB-affected lemon scions survived and 70% of the inoculated rootstocks were infected at 6 months after grafted using HLB-affected scions with high Las bacterial titers. The results also showed that plant growth regulators (PGRs) increased the survival rates of the grafted scions, but had no effects on the infection rates. 2. Screening antimicrobial compounds against Las bacteria Using the above two screening systems, several chemicals were evaluated for control of Las bacteria in the greenhouse, including antibiotics (Penicillin, Streptomycin, Oxytetracycline, Kasumycin, Metronidazole), a biocide (DBNPA), two peptides (D2A21 and D4E1), two fungicides (Zineb and captain) and Systemic Acquired Resistance (SAR) substances (SA, antiguard and ortho-phenylphenol). Some were effective, such as penicillin and streptomycin, both peptides and Oxytetracycline; some were partially effective, such as DBNPA. The SAR substances, Metronidazole and Zineb were not effective in this research. Kasumycin and Captain need to be tested further. 3. Monitoring the antibiotic effects in the field: Two kinds of antibiotic combinations, PS (Penicillin and Streptomycin) and KO (Kasumycin and Oxytetracycline), were tested in the field at the USHRL farm. The primary results showed that application of the PS via trunk injection eliminated or suppressed the Las bacterium in the HLB-affected citrus plants. The residues of antibiotics were also tested and were not detected in fruit after one months. The field trial is still in progress. Two papers has been or will be published in Phytopathology 2010 and 2011. Four abstracts or posters have been or will be presented at International Citrus meetings or the APS annual meeting. Future research: Continue to monitor treated, field trees; develop an improved method for treating trees with antibiotics; test additional antimicrobial compounds; test antimicrobial compounds in combination with growth enhancing molecules.
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