During this 2nd year, data were collected from field experiment 1 (E1) until Nov/11 when all trees from experimental area were eradicated and E1 finished. The results from E1 have been compared with the results of other similar experiment (E 2) where HLB epidemics will be followed until 2012. While E1 have been carried out in a region with high external inoculum pressure because of its proximity with groves without HLB management, E2 is in a region with lower external inoculum pressure, located in the middle of a large farm with regional disease management (4 to 14 annual insecticide applications and 3 to 4 annual HLB-symptomatic trees eradication in the area up to 2 km surrounded the experimental area). The main results so far indicate that area-wild management of HLB (AWM) is essential to control the disease: i) The disease epidemics started 299 days later in area under AWM. In E1 the disease epidemics started in average about 587 days after planting, while in E2 it started later, 886 days after planting. ii) The disease epidemics were slower in area under AWM. The annual disease progress rate estimated by Gompertz model reduced 75% (1.18 for E1 and 0.30 for E2) and the cumulative incidence of HLB-symptomatic trees was reduced in 91% (E1 ‘ 76.9% and 53.1% and E2 ‘ 6.3% and 4.6% for plots without and with ACP control, respectively). iii) The local program for ACP control in E1 was efficient to reduce the number of adult psyllids captured on yellow stick traps in 81% and to reduce the number of eggs and nymphs observed on new shoots in 95%. However this local vector control reduced HLB-incidence in only 31%. iv) AWM of ACP increased the efficiency of local control measures because reduces the migrant psyllid population. The cumulative number of caught ACP adults/trap/assessment in plots without vector control was 0.46 and 0.12 for E1 and E2; and ACP population is decreased year after year even in plots without insecticide application). v) Differences on the time that a symptomatic tree remained exposed in the field before be eliminated were observed among different frequencies of local inoculum reduction. However, such differences did not result in significant differences on HLB progress rate and final HLB incidence among different frequencies of local inoculum reduction in both experiments. vi) AWM of bacterial inoculum (symptomatic trees) reduced the migrant infective psyllid population that reaches the local plots. For E1, in average, 5% of all psyllids captured on yellow stick traps of from the winter/07 to spring/10 tested positive for the presence of Candidatus Liberibacter asiaticus by conventional PCR. However, no psyllid sample was positive for CLas in E2. Infective ACPs were found both in plots with and without vector control program. This result could explain why even with similar population of adults ACP in plots with vector control (0.08 in E1 and 0.09 in E2), the incidence of HLB-symptomatic trees were much lower in vector controlled plots of E2 (53.1% in E1 and 4.6% in E2). vii) AWM reduced the control costs because with less intensive vector control program (insecticide sprays every 28 days, or even no insecticide sprays) it was possible to be more efficient than a high intensive vector control program (insecticide sprays every 14 days) applied locally within a region without regional management. viii) AWM allowed solid block replanting with the guarantee of future yield. In plots of E2 without and with vector control the yield still increasing (2 ton/ha in the 1st, 16 in the 2nd and 38 in the 3rd harvest) while in plots of E1 the yield decreased year after year (2 ton/ha in the 1st, 9 in the 2nd and 10 in the 3rd harvest for plots with insecticide application, and 2 ton/ha in the 1st, 4 in the 2nd and 3 in the 3rd harvest for plots without insecticide application).A paper with the temporal analysis of both experiments is on preparation. The results of this project were also being presented to growers to help the establishment of growers’ groups for AWM.
1) Evaluation of screens impregnated with insecticide barriers. As explained in the previous report, the experiment is being conducted on two farms located in S’o Paulo. In the farm located in S’o Manuel, the experiment was installed on 12/14/2010 and nine evaluations were performed. In the area with insecticide barrier net, no psyllids were collected. However, in the area without the barrier, the capture of adults of ACP was also low, with only two individuals collected. In Descalvado, the experiment was started on 02/08/2011 and was performed four evaluations. In this area the capture was also very low and only one psyllid was collected in the area with barrier. The low ACP capture observed in both properties, probably is related to the large amount of rainfall that occurred during the evaluations, which may have interfered in the dispersal of D. citri in citrus groves in the neighboring properties. 2) Evaluate the impact of treatment of plants with systemic insecticides on the transmission of Ca. L. asiaticus by starved psyllids. The citrus trees that will be used in this experiment have already been purchased and will be delivered to Fundecitrus in early June, in the same month, the experiment will be installed. 3) Evaluation of the effectiveness of systemic insecticides and extraction of the sap of the phloem and xylem. This will be installed in the spring (outubro/2011), favorable time for absorption and translocation of systemic insecticides on citrus plants. The equipment for this experiment are being purchased.
Exp.1 ‘ During this second year project we just monthly looked for HLB symptoms and infection by PCR analysis. In the compartments where citrus plants served as primary source of inoculum of CLas or CLam we observed a predominance of infective psyllids and diseased plants with positive conventional PCR for CLas. In average 30.4% of psyllids collected from inoculum source plants and 8.4% collected from test plants were positive for CLas and no one for CLam. In average 14.4% of test plant were positive for CLas and 1.9% for CLam. For three Clam citrus infected plants, two had also CLas in a mix infection. Average Ct value for leaves with CLas were 24.7 and for CLam 33.7, indicating a higher titer for CLas than for CLam. In compartment where Murraya exotica served as source of inoculum, 46.0% and 9.4% of psyllids collected respectively in source plants and test plants were PCR positive for CLam, whereas in compartment where Citrus sinensis served as source of inoculum, 6.35 and 4.7% of psyllids collected respectively in source plants and test plants were PCR positive for CLam. 8.2% of test plants were PCR positive for CLam when inoculum source was Murraya exotica and up to now no infected test plant was detected when citrus plants served as primary source of inoculum of CLam. For this experiment, symptoms observation and leaf sampling for PCR analysis will be done at least until Dec/11. New inoculum source Citrus and Murraya plants were prepared to repeat this experiment. Because we were not successful to obtain Murraya infected with CLas after many attempts by grafting or natural inoculations, we decided to replicate the first experiment with the same treatments; however we used higher and older source of inoculum plants and 100 test plants per compartment. The replication was started in Jan/11 with the first release of HLB-free ACPs. Exp. 2- Emerging ACP adults from nymphs reared on inoculum sources plants were used for inoculation in Mar/10. Until now no symptomatic test plant was observed. Exp. 3 ‘ During this year many problems with inoculum sources, ACP rearing, bacterial acquisition and screenhouse wind damages made impossible the re-inoculation of the three screenhouse protected sweet orange cultivars (Hamlin, Pera and Valencia) at different ages (planted in 1999, 2004 and 2006) with CLas or CLam by D. citri. Monthly assessments for symptom severity have been done, but no HLB-symptoms were observed yet on inoculated trees. Also, leaf samples have been collected to detect the presence of Liberibacter species on inoculated shoot. New inoculation of these trees is planned in Jun/11. Some symptomatic trees that appeared before the inoculation were maintained in the screenhouse and the severity progress was assessed during last year project. For Hamlin/Rangpur 99, the annual severity increased from 24.3 to 27.5% (average of 7 trees); for Valencia/Rangpur 99, from 24.5 to 38.5% (average of 5 trees); and for Hamlin/Rangpur 04, from 35.0 to 57.5% (average of 2 trees). As an alternative for this experiment, 30 trees from each five citrus blocks at different scion/rootstock combinations (Hamlin/Swingle 07, Valencia/Volkamer 07, Valencia/Swingle 07, Valencia/Swingle 99, Valencia/Swingle 95), showing very low symptoms severity, were selected in Jun/10 in farms without removal of symptomatic trees but with strong ACP control program. After one year, the disease severity increased in average from 6.2 to 7.5% for Val/Sw 95, from 4.6 to 8.5% for Val/Sw 99, from 7.9 to 15.3% for Val/Sw 07, from 8.6 to 19.3% for Val/Volk 07, and from 12.8 to 19.2% for Ham/Sw 07. As expected, the disease severity progress is faster in younger trees. Assessments of disease severity and yield (healthy versus diseased trees) will be continued for more years to allow modeling of disease severity progress.
During the first year of our CRDF funded project, we have demonstrated that we currently have the tools necessary to greatly reduce the likelihood of young trees from becoming infected with HLB; the focus now is to determine the most cost-effective (and practical) manner for Florida citrus growers to achieve this goal in order to maintain the long-term viability of the Florida citrus industry. During 2010, we began by evaluating the most effective way to protect young trees from psyllids using soil-applied systemic insecticides. In these evaluations we used three different active ingredients, imidacloprid (Admire Pro), thiamethoxam (Platinum) and clothianidin (Belay). While most growers have had extensive experience with imidacloprid products, thiamethoxam was labeled for use in citrus in 2009 and clothianidin was registered for use on non-bearing citrus most recently in 2011. Due to the differences in the water solubility of these products (differences in availability and rate of uptake by the citrus root system), and our past success using these products via different application methods, we examined three different application methods for the most effective use of these products; soil drench (standard), soil band spray, and trunk application. The use of trunk applications was examined as a result of reports from South Africa touting trunk applications of imidacloprid (Confidor) as providing several MONTHS of residual control of the African citrus psyllid. In our trial work, we obtained the South African formulation (Confidor) and compared the efficacy of that product, using rates typical to those applied in S.A., to the products available for use in the U.S. For all three active ingredients and application methods evaluated, soil drench and trunk applications were most effective and consistent. Regardless of the particular product used, our results suggest that Florida citrus growers using soil-band applications of any of these three neonicotinoids will likely experience significant variation in psyllid control (failures) on a tree-by-tree basis and thus should not use this application method until further work on application volumes and subsequent irrigation practices can be investigated to make this method of application more reliable. While Florida citrus growers now have 3 “neonics” that can provide nearly season-long control of psyllids, additional control methods are needed to prevent HLB infection as neonic levels decline between applications and also to minimize the likelihood of resistance to this important group of pesticides that can be used for young tree protection. [Ongoing work in our CRDF funded project Huanglongbing: Understanding the vector-pathogen interaction… has shown that all 3 of these neonics can disrupt psyllid feeding behavior such that pathogen transmission is unlikley to occur.] As part of the overall goal of the current project, we are investigating the use of products that could potentially deter psyllid feeding in addition to that provided by systemic neonic products, particularly between neonic applications. The results of choice and no-choice experiments in the laboratory have demonstrated that the use of our primary psyllid repellent of choice can provide relatively extended and efficient reduction in psyllid feeding. These results have been further confirmed using EPG monitors to demonstrate a reduction in psyllid (phloem) feeding behaviors responsible for successful transmission of the HLB pathogen. This work is being continued in 2011 in field studies investigating these methods and the benefit of supplemental foliar sprays of different modes of action for protection young trees from HLB infection prior to reaching fruit-bearing age.
A series of greenhouse research experiments have been completed that show that a number of commercial formulations of plant growth regulators (PGRs) (GA biosynthesis inhibitors) reduce Asian citrus psyllid fitness. Specifically, we found that two of the PGRs tested (prohexadione calcium and mefluidide) reduced ACP fecundity and survivorship while two others, uniconazole and paclobutrazol, reduced fecundity or survivorship, respectively. These results have been summarized in a manuscript that has been submitted to the Entomological Society of America for publication in a peer reviewed journal. A follow-up study to determine the duration of efficacy of these treatments has recently been completed using one of the PGRs (prohexadione calcium). Unfortunately, we had very poor egg laying in all treatments, including untreated control trees, and the experiment was unsuccessful. We are trying to determine why this happened and repeat the experiment. An experiment has been completed to begin to determine what changes are occurring within plants that elicit the observed changes in psyllid fitness. Large container grown trees were treated with prohexadione calcium and tissue samples were harvested at 3 day intervals. The samples have been analyzed for nutrients and free amino acid content. We are still working on analyzing phenolic and flavonoid contents as well. Data analysis of the amino acids has not progressed as quickly as we had anticipated, but we will have them complete by the end of the project year. Results of this study will be used to develop further studies to determine the basis for the observed effects to be conducted in both field and greenhouse studies this summer. New work is being developed to determine whether the effects of PGRs on psyllid fitness correspond with changes in either acquisition or transmission of Candidatus Liberibacter asiaticus (Las). The first step in preparing for that line of research is to develop a population of Las-infected trees that can be used in acquisition studies. Greenhouse grown Las-infected trees used as infected budwood source material has been confirmed Las+ by PCR . Budwood from these trees has been harvested and used to graft inoculate a population of citrus trees. We are sampling these trees periodically for confirmation of Las transmission by PCR. Psyllid acquisition studies will proceed as soon as the new plant material has been successfully infected. We anticipate that occurring during the next quarter. In the interim, a population of ACP is being maintained and increased for use as soon as the plant material is ready. Field trials are planned for 2011 to test the efficacy of the PGRs against field populations of ACP. This trial was attempted in 2010, but we were unable to develop a sufficient ACP population in our field plots due to area wide ACP management. If this is the situation again this season, we will cage psyllids on treated trees to make the assessments. This trial will begin in mid-June or at the onset of the rainy season and summer flush development.
Oviposition and nymphal development experiments were conducted that included topical applications of dsRNA targeting specific psyllid genes. Elevated psyllid nymphal mortality was observed in plants on which dsRNA targeting distinct psyllid genes was applied to the soil of small potted citrus plants. This mortality was seen in the early instars but not later in nymphal development. Ultimately, adult psyllids did emerge from the surviving nymphs, but the number of emerging adults was reduced significantly (greater than 60%) as compared to plants either treated with water or dsRNA with a sequence that did not match any known psyllid gene. These experiments are being repeated. Continued bioinformatic analysis of psyllid transcriptome response to dsRNA feeding shows the major perturbations in the digestive tract gene regulation are in the pathways related to the genes being targeted. Observed changes include the apparent up-regulation of genes in the same pathway as the targeted gene showing how the cells are trying to compensate for the loss of function of this pathway due to dsRNA inhibition. Finally, field experiments have been initiated to test the effectiveness of topically applied dsRNA as a psyllid control strategy. Trees have been treated and performance is being evaluated.
The data pertaining to low volume field trials of the 2009 and 2010 seasons were analyzed to establish the relationship between the weather parameters and efficacy of the Asian citrus psyllid (ACP) control. Throughout the trials, application time wind speed varied from 0.9 ‘ 5.9 m/s and relative humidity from 87.6 to 91.3%. Mortality of the adult ACP at day-3 was not correlated with the humidity, but was significantly correlated with humidity at day-28, i.e., higher humidity resulted in better residual ACP control. Considering both the day-3 and day-28 efficacy results, wind speed did not appear to have a meaningful correlation with ACP control. Furthermore, the control of ACP nymphs was not affected significantly by the weather parameters. Air temperature at the time of application did not have a significant effect on mortality of either nymph or adult ACP. For the five top ranked treatments, the lowest relative humidity was 91.5% and the highest wind speed 1.8 m/s. The most effective application against both life stages occurred during meteorological conditions of 94.5% relative humidity and 0.9 m/s ambient wind speed. Data analysis will be continued to investigate the effect of post-treatment weather conditions on residual control of psyllids.
This project was designed to examine the potential disease control of citrus huanglongbing (HLB) by interplanting citrus with guava. In Vietnam guava has been shown to be an effective deterrent to HLB, slowing the disease and keeping plantings alive for up to 15 years that normally succumb in 2-3 year. For all plots and experiments, Guava trees, (Vietnamese white cultivar) were propagated and grown to appropriate size requiring ~1 year. Both nursery and field citrus trees are assayed for HLB every 60 days, and have been assayed multiple times. Psyllid populations are monitored continuously every 2 weeks to document repulsion of the vector. Results: Guava vs no guava nurseries: Two nursery sites, a guava protected citrus nursery versus an unprotected nursery, have were established with disease free, PCR-negative citrus trees (2 sweet orange and 1 grapefruit cultivars) in June 2009 and were located in the protected and unprotected plots. The guava trees were grown to appropriate size as indicated in Vietnam prior to outplanintg. To date HLB appears to be progressing more slowly in nursery plots interplanted with guava than in non interplanted plots. The freezes discussed below did not adversely affect these nursery plots. Citrus/guava interplantings: 2 commercial plantings with multiple replications were established but due to freezes and property sales these plantings are no longer viable. A third trial planting was established at the USHRL Picos Farm in Fort Pierce. The Picos plot was interplanted with citrus in August 2009. Severe frosts during 2008/2009 and again during 2009/2010 winters affected the USHRL plots and caused a delay in the experiment. A final hard freeze during the 2010/2011 season killed most of the guava trees. Data analysis to date indicates no differences were observed among treatments, i.e., guava interplanted vs. non-interplanted plots prior to the final demise of the plots. Our interpretation is that Florida is actually a subtropical environment, prone to intermittent freezes and cool or cold temperatures. Whereas, Vietnam and Indonesia, where the guava effect seems to work, are truly tropical without such broad temperature swings. After freezes it takes a considerable time to either replant guava or for the freeze damage guava to recover. Even during cool weather guava trees are very sensitive and do not continue to flourish and grow. It is the new flush of guava which appears to be the best at producing ACP repellent volatiles. Cool or freezing temperatures inhibits volatile production and thus the citrus crop is left unprotected from ACP. While guava not be a viable deterrent as an intercrop, it still may be possible to identify individual volatiles from guava that might be useful under field applications as chemical applications. We are now switching direction slightly to investigate other more temperate Myrtaceous plant species that are more cold tolerant and might be useful as intercrops. Research continues using a Y-tube olfactometer to continue to investigate guava volatiles as repellents of the psyllid as well as to investigate the feasibility of other Myrtaceous plants.
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.
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