This project was designed to examine the potential disease control of citrus huanglongbing (HLB) by interplanting citrus with guava as previously demonstrated in Vietnam and Indonesia. Guava was shown to repel psyllid vectors and slow the disease, extending the economic life of plantings by several years. White guava trees were brought back to Florida from Vietnam under permit, propagated and both nursery and field citrus trees were assayed for HLB every 60 days, and have been assayed multiple times. Psyllid populations were monitored continuously ea. 2 weeks . Results: Guava/commercial citrus interplantings: with multiple replications were established but due to freezes and property sales these plantings were not viable and were discontinued. 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 indicated no differences were observed among treatments, i.e., guava interplanted vs. non-interplanted plots prior to the final demise of the plots. Guava vs no guava nurseries: Two nursery sites, a guava protected citrus nursery versus an unprotected nursery, 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. HLB progressed more slowly in nursery plots interplanted with guava than in non-interplanted plots. The freezes discussed below did not adversely affect these nursery plots as they were more protected. Interpretation: 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. In mid-2011, we began examining more temperate, i.e., cold tolerant Myrtaceous plant species as citrus intercrops to determine If alternative Myrtaceous plants could be identified to be repellent to ACP. We abandoned this research when CRDF discontinued funding for this project.
We have continued to examine the latency period of Las in the psyllid by examining replication of Las in psyllid nymphs and adults. To examine latency in nymphs, ten adult ACP pairs (males + females) caged on young leaves of Las-infected ‘Valencia’ sweet orange plants. After a 5 d oviposition period, adult ACP were removed. Nymphs were allowed to develop on infected plants for varying acquisition access periods. Subsamples of nymphs were collected periodically and remaining nymphs were transferred to healthy or infected plants. Ten adults from each replicate were collected immediately after emergence and remaining adults were subsampled and transferred to healthy (uninfected) plants every 5 d, for 45 d. Similarly, latency in adult psyllids was assessed by enclosing one hundred newly emerged adults on Las-infected plants for various acquisition access periods. Subsamples of adults were collected every 5 d and remaining adults were and transferred to healthy (uninfected) plants. Quantitative real-time PCR (qPCR) is being used to to assess Las titers in all psyllids and recipient plants. Each experiment was replicated five times on different plants. Psyllid bioassays and testing are ongoing. In addition to examining psyllid latency and Las replication, we have continued experiments to assess psyllid suitability as a host for Las by examining the effect of endosymbionts on psyllid survival and transmission. Microinjections of psyllids with antibiotics are currently being used to clear psyllids of symbionts for fitness, acquisition, and inoculation bioassays comparing ‘natural’ verses aposymbiotic psyllids. Concurrently, we are developing breeding lines of psyllids to whether there is a genetic basis for vector efficiency.
Data collection from the 10-acre young tree protection multi-year trial continues. Since the October 2011 update, foliar treatments have been applied as planned on 3 separate dates (9 total applications since planting). Soil-applied neonicotinoids have been applied on two separate dates (5 total applications since planting). Leaf samples from plots continue to be collected at two week intervals for pesticide residue analysis. Psyllid and leafminer counts have been continued every two weeks. Psyllid populations continue to remain below detectable levels. However, leafminer damage has remained extremely high, particularly in the control and foliar-applied broad spectrum insecticide treatments. As a result, significant differences were present in the trees growth data recently collected that is most likely attributable to the severe damage caused by leafminer in certain treatments. As a result, in November, the entire block was sprayed with abamectin once to help get the leafminer population under control. PCR testing of leaf samples from our plots has failed to detect any Las positive trees in any of the treatments (including controls) to date. Laboratory bioassays with the psyllid deterrent material used in two of the treatments in the field trial were conducted to determine the effect on psyllid host plant selection and psyllid feeding behavior. Effects on host plant selection were examined using choice test with treated and untreated plants in the same cage wherein psyllids were released. In choice tests, psyllids overwhelming chose to land on and subsequently feed on untreated plants by a factor of 6:1. Effects on feeding behavior were examined using an EPG monitor which showed that psyllid feeding behavior was disrupted on plants treated with the deterrent such that phloem feeding did not occur. Additional experiments were conducted that point to a likely mechanism (explanation) for how this feeding disruption occurred. A third field trial comparing application methods and rates of neonicotinoid insecticides, was initiated in January. Given the overall low psyllid population in the plots at this time of year, the primary goal was to compare pesticide rate of uptake of the different application methods in the winter months which was determined by collection of leaves for analysis of pesticide residue in the plant. We also began work looking at the effects of climate (time of year) on the efficacy of pesticide applications. In January, foliar applications were made in the field to replicated plots. Treatments included an organophosphate insecticide, a pyrethroid insecticide and a neonicotinoid. At 1, 7, 14, 21, and 28 days after application, adult psyllids will be caged on treated plants and then later recovered to determine the actual residual activity of these pesticides. This will be repeated throughout the year to determine if the duration of efficacy changes with the season.
The CHMA assistant position has been advertised twice to ensure all qualified applicants have been reached. Interviews for three candidates have been scheduled. No funds have been spent from this grant to date. No further action to report at this time.
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. The following is an update of ongoing field and laboratory experiments. The potential for ACP resistance is uppermost in many grower’s minds and management programs are based on rotation of modes of action. Nevertheless, many practical questions remain on how this is best accomplished. Experiments are underway to 1) compare selection rates for resistance using mixture (AgriFlex) versus rotation of its two components, and 2) evaluate stability of insecticide resistance and number of generations required to return tolerant populations to susceptibility. We applied the first round of LD25 applications on 7 Dec. This month we are testing a sample of the population with the LD80 to determine if resistance has begun. If resistance is not present, we will again treat our psyllid populations with LD25 applications of their respective insecticide. The plan is to evaluate rate of resistance induction in caged psyllids using the LC25 dose, then using discriminating dose bioassays to monitor response to 5 treatments: the premix, rotation, each insecticide alone, and a check. Later, insecticides will be withdrawn and return to susceptibility evaluated. Citrus leafminer (CLM) incidence and damage has been increasing, possibly due to increased use of broad spectrum insecticides to control ACP. Canker is also on the rise and growers are demanding assistance with management of CLM, thought to exacerbate the disease. We have been monitoring CLM using sticky card pheromone traps in citrus groves as well as a natural preserve (Okaloacoochee Slough State Forest) in an attempt to determine effective distances from source to trap. In the process we have found what we believe to be 5 different leafminer species attracted to the pheromone lure. Therefore we embarked on an investigation using of bucket pheromone traps to collect identifiable specimens in different locations. Representative moths will then be keyed to species by a taxonomist and subject to DNA bar coding. A botanist has identified the species of plants where mines are found, so that we have a better indication of the species present near the pheromone traps. Within the next few months, these pheromone will be used in conjunction with mark and recapture experiments to determine distance traveled by CLM, and development of a preliminary degree-day model. We have started a colony of CLM to to rear the parasitoid Citrastichus phyllocnistoides and support a program for monitoring CLM susceptibility to key insecticides. And, this spring we will use a diagnostic dose to monitor resistance in field populations of CLM exposed to intensive versus modest insecticide use. We are collaborating with the DPI CHRP program to evaluate results of the cooperative (area wide) ACP management program, in SW Florida, now the Gulf CHMA which uses a sampling protocol of 50 taps/block. We now present this data spatially and temporally by way of interactive GIS maps available on our website http://swfrec.ifas.ufl.edu/entomology/extension/chma/ for growers to use.
Low volume (LV) aerial and ground sprays have become an important method of application in Florida citrus. We continue our evaluations of LV application of 435 horticultural mineral oil (HMO) which has shown promising results the last 3 years. This report documents updated results from the fifth trial begun on February 2011 in a 10.9 acre plot of ‘Valencia’ orange in Lee County. The efficacy of low volume spray spray of 435 horticultural spray oil (HMO) with the Grower Standard and an Untreated control are being compared. This trial is the first with sufficiently high ACP populations to assess the ability of LV oil sprays to provide suppression. Three sprays of 435 oil (12, 20 Oct @ 2gal/ac; 3 Nov @ 2gal/ac) have been completed since the last report. No insecticide sprays have been applied to the Grower Standard plots since the last report. All plots will receive a dormant spray this month of Danital on 9 Jan in conformance with IFAS recommendations. Mean adult psyllid populations over the last 3 months were 0.11 +/- 0.023, 0.07+/- 0.023 and 0.203+/-0.023 for the Grower Standard, Oil, and Untreated Check respectively. The Grower Standard (p = 0.005) and Oil treatments (p < 0.0001) had significantly fewer psyllids than the Untreated Check. Thus, the low volume oil treatments are suppressing ACP as effectively as the Grower Standard. Resets were sampled in Oct for percent HLB (n= 40, Grower Standard; n = 34, Oil; n = 39 Untreated). Results showed no significant differences between treatments and incidence of infection was low (<3%). There was also no difference in Ct titer with values ranging from 35 for Untreated to 37 for Oil treatments. Citrus leafminer damage assessments for Oct were unobtainable due to low density of flush. There were two peak flights since the last report (13 Oct and 15 Nov). Moth flight in the Oil treated plots was significantly (p < 0.05) lower than the Grower Standard and Untreated plots for the sixth generation (10 Nov) in spite of higher flush density. This result indicates that oil is contributing to CLM egg and larvae mortality. Monitoring of traps is continuing over winter to follow moth phenology and determine the effect of treatments on CLM populations.
Research targeting the development of a new Asian citrus psyllid control strategy based on blocking salivary sheath formation was advanced in two areas. First, Compositional analysis has shown that this sheath is synthesized as a two part structure each with different composition. The first part is a flange that is initially secreted on the surface of the leaf. This secretion is highly autofluorescent and sensitive to alkaline treatment. Once the leaf is penetrated, the sheath composition changes to a non-autofluorescent structure that is more resistant to alkaline hydrolysis. This sheath section is primarily carbohydrate in structure. Compositional and structural research will be completed during the next year and this information will be used to identify ways in which to inhibit its formation. Second, an artificial diet bioassay has been used to screen a positional scanning peptide library to identify peptide inhibitors of salivary sheath formation and/or psyllid feeding behavior. Initial screenings with highly complex decapeptide mixtures has shown activity against feeding and salivary sheath formation. Using a positional scanning method developed by Torrey Pines Institute for Molecular Studies, the complexity of these decapetide libraries is being deconvoluted to identify the specific peptides responsible for the biological activity. During the next year, specific peptides will be identified. Once this is identified, this sequence will be used to construct a synthetic gene encoding this peptide for use in transgenic plant construction and will be used to test topical application strategies to block this feeding process
The ‘Hamlin’ orange block at SWFREC receiving the Boyd cocktail treatments was harvested in December before Christmas. By harvesting in December we avoided the January 4, 2012 Freeze in Immokalee that we experienced 25 degrees F. Fruit yield on 8.2 foot tall trees from the better treatments averaged about 2 boxes per tree. The better treatments were those that contained Macro nutrients as DKP + KNO3, micro-nutrients Mg, Mn, Zn, Mo, B, and a Phosphite. Fruit and juice quality from the ‘Hamlin’ trial at SWFREC has been sampled and will be reported in the next quarterly report. Citrus canker was a significant factor in our trial this year for the first time. Fruit loss among treatments varied from 40% in less vigorous trees to between 60% to 75% fruit loss in treatments stimulating more vigorous growth. Treatments with macro-nutrients from only spray grade foliar applied KNO3 + the micro-nutrients had less loss of fruit to canker. The less vigorous trees with less flush carried the larger fruit load with less fruit drop in the presence of citrus canker. The highest yield per tree for Hamlin continues to be treatments 2 (complete Boyd cocktail minus the SARs), treatment 9 (complete Boyd cocktail minus hydrogen peroxide, and treatment 1 (complete Boyd cocktail. These three treatments consistently are among the four highest yielding during the past three years. Treatments 4, 5, 6, and 8 which do not contain the foliar applied nutrients Mg, Mn, Zn, Mo, and B are among the lower yielding trees. We are well into the 4th year of a replicated experiment in a 12-acre experiment commercial block of 8-year-old ‘Valencia’ oranges on ‘Swingle’ to test effects of two factors: (1) micro-nutrients + systemic acquired resistance inducers, and (2) Asian citrus psyllid (ACP) chemical control on ACP populations on Can. Libericacter asiaticus (CLas) titer, and plant yield. While we are continuing with the experiment, results from the first 3 years are being written up for publication. Except for 14 Dec, psyllid populations in the nutritional only plots reached the 0.20 threshold during each sampling period 6Oct – 29Dec. Insecticide and Insecticide+nutritional had significantly (P< 0.05) fewer adult ACP than control or nutritional only on dates 6, 20 Oct; 3 Nov, and 29 Dec. All three treatments had significantly (P < 0.05) fewer ACP than control on 1, 14 Dec. Since our last report we have not sprayed any treatments, but will be applying a dormant spray of Danitol in plots designated for insecticide treatment on 15 Jan. Resets planted (June 2010) were tested for HLB detection (19 Oct) but showed no significant treatment effect on percentage PCR positive for HLB (20% - 52% infection). For adult trees (9 years old), a lower incidence of HLB (80 and 86%) was seen for nutritional and insecticide plus nutritional treatments compared to the untreated (98%) or insecticide only (94%) plots. For adult trees, Ct values were significantly lower for Untreated (24.34) and Insecticide only plots (24.83). However, there were no significant differences between the insecticide plus nutritional plots (24.83) and nutritional only plots (26.81). For the resets, there were no significant differences in Ct values (range 28.88 - 31.80).
This report marks the beginning of the third and final year of a project on protecting newly planted citrus trees from Asian citrus psyllid (ACP) and huanglongbing (HLB). The project is collaborative between USDA-ARS (Hall) and University of Florida (Stansly). Update on USDA-ARS activities. Two experiments are being concluded by USDA-ARS in the Indian River citrus area at a grove just west of Fort Pierce. For research purposes, most of the grove is under a minimal ACP management program and HLB-infected trees are not removed. A detailed summary of the two experiments (as of late summer 2011) was presented in the September 2011 Annual Report. Since that time, notable is that regardless of the particular psyllid management program studied in each experiment, the percentage of trees infected by HLB increased to more than 65% within 39 months after planting in one experiment (infected trees removed as they were found and not replanted) and to nearly 100% within only 26 months after planting in the second experiment (infected trees not removed). The results support that a grower will have difficulty protecting new plantings from ACP and HLB if concerted efforts are not made to control ACP and HLB on an area-wide basis in the vicinity of a new planting. For more information on the specifics of the two experiments, refer to the September 2010 progress report. Update on UF activities. Insecticides currently remain a principle tactic used for ACP/HLB management. Growers need information on when it is best to apply insecticides, how to apply them, and the best insecticides to use. Minimizing the use of a particular pesticide and rotating modes of action (MOA) are considered critical in resistance management. New insecticides with novel modes of action are desired. Research in newly planted citrus showed that a new DuPont insecticide, Cyazypyr (DPX-HGW86, cyantraniliprole), is very active against both ACP and citrus leafminer, being as good as or better than Platinum or Admire Pro. In one experiment, a comparison of young trees treated four times annually with different rotational schedules of Admire, Platinum and Cyazypyr indicates that, regardless of the order that the insecticides were applied, significant control of ACP was achieved as compared to ACP levels in untreated trees; also, lower percentages of trees tested HLB positive after 1.5 years in plots receiving insecticides (0 to 8% trees infected) than in plots of trees untreated (28% trees infected). This insecticide is of a novel MOA (diamide chemical class) and is effective against a number of important types of pests including fruit flies, leafminers, leaf-feeding beetles, whiteflies, hoppers, thrips and weevils. A citrus label for Cyazypyr is anticipated.
Experiment 2 (within HLB-Area-Wide Management AWM). The incidence of HLB did not increase in the last 3 months during spring season (October to December/11), even in plots without insecticide application. The same was observed for CVC incidence. The HLB progress rate still low (cumulative incidence from 6.3% in November/10 to 7.3% in December/11 for plots without ACP control; and from 4.5% to 5.3% for plots with ACP control). The AWM of ACP has kept the ACP population density very low (almost zero) and deccelerated in the last two years, even in the plots without ACP control and with abundant new shoots at spring. A manuscript with the results of Experiment 1 combined with experiment 2 was writen and has been revised by all co-authors and will be submmitted to scientific journal until February. For Year 3, we will continue collecting data from Experiment 2 under regional management, analyzing the spatio-temporal disease and economics data from both experiments.
This is a one-year project with the objective of developing a method for controlling the Asian Citrus Psyllid (Diaphorina Citri Kuwayama) population which vectors the disease Huanglongbing (HLB). This phase of the project involves screening dsRNA constructs that will knock-out essential mRNAs, following feeding, by RNA interference. More than 50 targets have been pre-selected by experts in the field. The initial screening phase, which began in August 2011, will continue through the first three quarters (Aug. 2011 to April 2012). Repeat experiments will occur in the last quarter (April 2012 to July 2012). Publication of findings will also be performed in the final quarter. Preliminary data show a remarkable increase in the mortality of Psyllid populations in a controlled environment, following dsRNA feeding. The mortality rate of insects feeding on water alone was much greater than those feeding on an artificial diet. Alternatively, diets containing several of the selected dsRNAs were shown to increase mortality above diet alone, but did not exceed water alone. Diets containing 3 – 48ng/uL of a specific dsRNA that show 20% higher mortality than diet alone after 3 days and 40% higher mortality than diet alone after 6 days were found to include: nutrient transporters such as Aquaporin (Water Transporter) and a Sugar Transporter as well as Electron Transport-Respiratory and Iron sequestering proteins such as Succinate Dehydroginase and Rieske. Higher than expected mortality using non-specific dsRNA sequences has also been observed obscuring a definitive mechanistic interpretation. With further trials we hope to better understand this process.
To assess the impact of insecticides used for psyllid control on non targets, replicated blocks of mature citrus untreated or treated with foliar sprays of insecticides, horticultural oils, and nutritionals were sampled for psyllids, citrus rust mites (CRM), citrus red mite, predatory mites, snow scale, chaff scale, Glover scale, purple scale, citrus blackflies, whiteflies, mealybugs, as well as their natural enemies and fruit damage at two conventional groves in Hendry County and one each in Lee and Collier Counties. Threshold levels of psyllid populations were not reached in two treatments of two Hendry county locations. However plots designated for calendar sprays at both locations received a rotation of insecticides recommended for ACP control applied every month: spirotetramat (Movento MPC) at 16 fl oz/ac + horticultural mineral oil 2% in October, carbaryl (Sevin 7XLR plus) at 0.75 gal/ac in November and phosmet (Imidan 70 W) at 1 lb/ac in December. These treatments provided significant suppression of psyllids and also impacted some non targets. In a block of ‘Earlygold’ orange, CRM, chaff scale and purple scale averaged 0.4 ‘ 0.1, 2 ‘ 0.3 and 1 ‘ 0.2 per lens field of fruit in the treated plots, respectively, compared to 1 ‘ 0.2, 2 ‘ 0.2 and 0.4 ‘ 0.1 in the untreated plots, respectively. In a ‘Valencia’ orange block, CRM, chaff scale and purple scale averaged 0 ‘ 0, 0.5 ‘ 0.1 and 0.3 ‘ 0.1 per lens field in the treated plots, respectively, compared to 0.4 ‘ 0.2, 0.7 ‘ 0.1 and 0.2 ‘ 0.1 in the untreated plots, respectively. Percent russeting from CRM averaged 21’ 2 and 35 ‘ 2 in the treated and untreated plots of ‘Earlygold’, respectively, and 14 ‘ 2 and 21 ‘ 2 in the treated and untreated plots of Valencia, respectively, indicating that insecticide treatments, probably spirotetramat, are also provided some protection from CRM. Similar impact was observed against leaf infestation with woolly whitefly. However, more scales particularly purple scale, were observed on fruits in the treated plots. Percent russeting averaged 35 ‘ 3, 36 ‘ 3, and 36 ‘ 3 in the plots treated with grower standard sprays, biweekly sprays of 435 oil or the untreated check in a block of ‘Valencia’ in Lee county, reflecting no treatment impact. Averages per lens field between treatments ranged from 0.1-0.4 for CRM and 0.2-0.3 for chaff and purple scales. Percent leaf infestation with woolly whitefly averaged 4-5% between treatments. The experiment in Collier county compares 4 treatments (1) Nutritional (2) Insecticides (3) Insecticides + Nutritionals and (4) Untreated control and uses insecticides currently recommended for psyllid control at threshold of 0.2 adults per tap sample and nutritional program developed by McKinnon Corporation averaging three sprays per year. CRM were high on fruits in the treatments using insecticides (0.2-0.5/lens field) compared to nutritionals only and the control (0.06-0.08/lens field), however, russeting was less in the insecticide treatments averaging 3-4% compared to 8-10% in nutritonal and control. Chaff scale averaged 0.5/lens field in insecticides only treatment compared to 1/lens field in the remaining three treatments. Purple scale averaged 0.2/lens field with the nutritional treatment and 0.1/lens field in the remaining three treatments. Percent leaf infestation with woolly whitefly averaged 10, 4, 4 and 2 in treatments 1, 2, 4 and 3, respectively, indicating some suppression with insecticides but increase with the nutritionals only treatment. Four studies comparing 43 foliar treatments of recommended and experimental insecticides against ACP and citrus leafminer were submitted for publication in the Journal of Arthropod Management Tests of the Entomological Society of America.
We continue to work on the objectives of 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 and integration of methods for assessing psyllid density, shoot density, and infestation rates into a user friendly system accessible to consultants and managers. The stem tap and vacuum sampling methods were compared for estimating ACP adults in two experimental blocks of two conventional groves in Hendry county, one a 35 acre block of ‘Early Gold’ and the other a 16 acre block of ‘Valencia’. A ‘tap sample’ count consisted of adult psyllids falling on a white clipboard placed under randomly chosen branches which were then struck 3 times with a length of PVC pipe. The vacuum sampler is made from a leaf blower and collects psyllids even at low populations. A single sample consists of 10, 1 second strikes on the canopy of a single tree. The number of ACP adults captured in suction sample were compared with average number of ACP adults detected in two tap samples conducted before and after the suction sample. Regression analysis indicated a strong positive linear relationship between the two methods on numbers of adults detected in both blocks. In the ‘Earlygold’ block, the relationship was best explained by the equation y = 9.816x + 1.522 (r2 = 0.61) where y = the suction sample and x = the tap sample. In other words, about 10 ACP via suction for each tap. Out of 109 samples conducted using each method, psyllids were observed in 29% (n=32) of the tap samples and 53% (n=58) of the suction samples. Psyllids averaged 1 ‘ 0.3 and 10 ‘ 4 per tap and vacuum sample, respectively. In “Valencia” block the relationship was best explained by the equation y = 14.79x + 0.044 (r2 = 0.74). Out of 96 samples conducted using each method, psyllids were observed in 34% (n=33) tap samples and 55% (n=53) vacuum samples. Psyllids averaged 0.7 ‘ 0.2 and 11 ‘ 4 per tap and vacuum sample, respectively. A pest scouting workshop in collaboration with Hendry county extension is planned for this spring to promote the use of proper sampling methods for effective pest management particularly ACP. Methods to monitor psyllids using tap sampling method and flush examination along with data sheets to record data have been posted at our website: swfrec.ifas.ufl.edu/entlab. Growers are using the sampling kits provided through SWFREC and IFAS extension and suggested data collected methods. Detailed comparisons of different sampling methods are provided in the EDIS document listed below. Arevalo, A. H, J. A. Qureshi and P. A. Stansly. 2011. Sampling Asian citrus psyllid (ACP) in Florida citrus groves. EDIS, http://edis.ifas.ufl.edu/in867.
Objectives of this project include: 1) scale up production of Tamarixia radiata to levels that will allow better assessment of the potential impact an augmentation program may have on the ACP population and ultimately the spread of HLB, 2) use genetic techniques to identify parasitoids recovered from the field to demonstrate establishment and effectiveness of released strains, and 3) pass on rearing technology to both private and public sectors to encourage production and an adequate supply of these parasitoids into the future. This quarter 30,793 wasps of the previously established strain of T. radiata from Taiwan and South Vietnam were produced in the colony at SWFREC, increasing the 2011 total to 22,393. These wasps were used for research, to maintain the colony and to release in treated and untreated plots of commercial experimental blocks in Collier, Lee and Hendry counties. This quarter, 17,108 wasps were released, increasing the number released in 2011 to 142,078. Additional field releases this quarter of 20,900 wasps from the Pakistan colony established at DPI, Gainesville increased the total number of Pakistani wasps released this year to 79,600. Wasps from the Pakistan colony were released at the SWFREC (Collier County). Fewer nymphs were available in the groves to assess parasitism rates this time of the year due to scarce flush and already suppressed populations of psyllid through effects of biological and chemical control during growing season. Incidence of parasitism based on adult emergence from feral nymphs in a 2 year old block of citrus at SWFREC during October averaged 21.5% (N=523) compared to a release block of a neighboring conventional grove which averaged less than 1% (N=555). In the same conventional grove in December, parasitism averaged 6.5% (N=62) in the blocks where releases were made compared to 5% (N=43) in the blocks without releases, probably indicating movement from the release blocks. Parasitism averaged 8% (N=63) in blocks that were untreated or treated only with nutritional sprays compared to 2.4% (N=42) in the blocks treated with insecticides for psyllid control. The recovered parasitoids were preserved in 95% ETOH and sent to Dr. Evan Braswell of USDA APHIS, Edinburg, TX, to characterized using molecular markers. We have been assisting OrangeCo in their efforts to mass rear T. radiata and observed their production and release system on two occasions this quarter. We also planned with them collaborative experiments to be undertaken this spring to determine the effects of release rates on psyllid populations which will be conducted this spring. The research will be undertaken with the assistance of a self-financed master’s student Ziyi Zhang AKA “Mike” with whom we had committee meeting Orange Co. chaired by Dr. Norm Leppla. Another master’s student, Xulin Chen, whose assistantship is being paid for by this project, has been taking courses in in Gainesville since August and has already undertaken a study of the use of CO2 for anesthetizing T. radiata to assist with manipulations during wasp rearing. Findings on the production, field release and evaluation of the parasitic wasp T. radiata against ACP in Florida were presented at the annual meeting of the Entomological Society of America held in Reno, Nevada, and at the Subregional Workshop “Biological Control in Huanglongbing” Recommendations for Central America held in San Carlos, Costa Rica. We also initiated two new colonies of the biparental colony of Diaphoencyrtus aligarhensis from Pakistan at SWFREC.
This is a one-year project. The overall objectives are to rapidly screen and evaluate chemical compounds for the control of citrus HLB using a graft-based screening method. In this quarter from Oct. 2011 to Jan. 2012, the research was focused on the chemical treatments of the second round in Sep. 2010 and the qPCR test in the first-round treatments in May, 2011. In the second round of the contest, twenty files were received on Sep. 15, 2011. Based on the rank of an expert panel and the action modes of the compounds, 16 compounds from 32 of these files listed (ranked higher than 0.17) were purchased and tested. Some compounds such as peptides in File 9932744_044 and lead compounds in File 9932744_066 and 9932744_070 could not be purchased, so they could not be tested. The grafting of the bud sticks treated with the above compounds have been done in December 6, 2011. To date, the grafted scions grew normally. In the first round of the contest, leaf samples of scions and inoculated plants treated with 22 compounds were taken for determining the Las bacterial titers by qPCR. The scion survival rate (%), the pathogen transmission efficiency (%) and the scion infection percentage (%) were also recorded. The primary results indicated that more than 60% of the scions survived and grew when treated with all forty compounds in the first round, except actidione (cycloheximide) at 50 mg/L (0%) and benzyl isothiocyanate at 50 mg/L (54.2%), which were retested at the lower concentrations of 25 mg/L. Ampicilin (Amp) and Rifampicin (Rim) were effective in reducing Las bacteria to undetectable levels in the HLB-affected citrus; Rifamycin (Rif) and Carbenicillin (Carb) were highly effective and lowered both bacterial titers and transmission rates. Nine tested compounds partly suppressed the Las bacterium, including Kanamycin (Kana), Colistin (Col), polymixin B (PMB), Hygromycin (Hyg), Isonicotinic acid hydrazide (INH), Rifaximin (Rix), Cycloserine (Cys), Quinoline (QUI) and Vanomycin (Van). More than 80% of the inoculated plants treated with the other nine compounds, including kasumin and gentamycin, were infected by Las bacterium and had high Las bacterial titers. The other grafted material will be tested soon.
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