Under Objective 1 and 2: Soil applications of SAR inducers at various rates and application frequencies were evaluated for control of canker in field trial of 3- or 4-yr old ‘Ray Ruby’ grapefruit trees in southeastern Florida. Reduction of foliar incidence of canker produced by one, two or four soil applications of the neonicotinoids, IMID and thiamethoxam (THIA), or acibenzolar-S-methyl (ASM, Actigard) was compared with 11 foliar sprays of copper hydroxide and streptomycin applied at 21-day intervals. In 2011 crop season, all treatments significantly reduced the incidence of foliar canker on the combined Spring-Summer-Fall flushes compared to the untreated control, depending on rate, frequency and timing of application on young grapefruit trees under canker epidemic conditions. Soil application of systemic neo-nicotinoid insecticides has also been demonstrated to induce SAR and provide canker control for bearing trees but use of higher rates of these systemic insecticides for young fruiting trees is currently restricted. A preliminary trial in 2011 with 5 yr-old fruiting grapefruit trees trees demonstrated the efficacy of trunk application for IMID, THIA and ASM at 3.5X the label rate per season to compensate for the larger tree volume. Trunk application was as effective for canker control on foliage as soil application and control matched that of 11 sprays of copper. The objective for current field research is to develop more effective suppression of fruit infection using trunk applications of neonicotinoids and non-insecticidal SAR inducers (e.g. ASM). . Under Objective 3, the integrated use of ASM, THIA and IMID soil applications was evaluated to increase and/or extend canker control in 3-yr-old grapefruit and 2-yr-old Vernia orange trees. The highest incidence of disease trees and/or leaves was in the non-treated check in each trial compared with a very low incidence of canker in the integrated SAR treatments. A field trial with soil applied neonicotinoids in Parana, Brazil was evaluated. IMID (Confidor) as a soil drench and IMID (Winner) applied to trunk gave comparable in disease control activity on 2-yr old Valencia orange trees, as well as, the other neonicotinoids tested, THIA and Clothianidin. Clothianidin (Belay) is now registered for use on non-bearing citrus in Florida, hence all of neonicotinoids registered for non-bearing citrus in Florida have been shown to have SAR-inducing activity against canker. In 2012 spring, field trials the rates and and timing of soil drenches and trunk treatment with neonicotinoids are congruent with recommendations for use of neonicotinods for systemic control of psyllids . Novel non-neonicotinoid insecticides and fungicides with demonstrated systemic activity against canker in greenhouse trials are under evaluation in addition to ASM for integration with neonicotinoids and foliar copper sprays to optimize canker control on non-bearing and young bearing trees.
This report is for July/2011. 1) Evaluation of screens impregnated with insecticide barriers. As explained in previous reports, the experiment is being conducted in two farms located in the Sao Paulo State. On the farm located in Sao Manuel 14 evaluations were performed. In the area with screen impregnated with insecticide barriers 2 insects were collected, and in the area without screen nothing was collected. In Descalvado 12 evaluations were performed, in a total of 2 and 1 psyllids collected in areas with and without barrier, respectively.
1) Evaluation of screens impregnated with insecticide barriers. This experiment has already been completed (see annual report sent on 2/2/12). 2) Evaluate the impact of treatment of plants with systemic insecticides on the transmission of Ca. L. asiaticus by starved psyllids. The transmission trials have already been completed. The test plants are being evaluated by PCR. 3) Determination of the concentration of pesticides present in the sap of the xylem and phloem of citrus plants and the lethal concentration to D. citri This experiment is delayed because the equipment for the extraction of plant sap is being imported. The device has already been bought, however the manufacturer has not delivered it yet. The experimental area has been selected and the experiment must be started in September (after Brazilian winter).
Exp.1 ‘ All test plants from the first trial were collected and submitted to real time PCR for the last time in January/2012. In the compartments where citrus plant were used as inoculum source of Las and Lam, the test plants were naturally more infected with Las than with Lam (0 and 3.8% of test plants infected with Lam and 9.6 and 19.2% of tested plants infected with Las). In the compartment with Murraya as source of inoculum of Lam, 8.2% of test plants got infected. The second trial is ongoing but there is no result yet. Also we had an infestation of Tamarixia radiata in our ACP breeding plants that completely devastated it and postponed the new releases of ACP into the compartments. We needed to restart our ACP HLB-free breeding. Exp. 2- Acquisition Period for Las and Lam. Different acquisition periods (AP) (30 min, 1h, 3h, 6h, 12h, 24h, 3 days, 7 days, 10 days and 14 days were tested. After these APs in sweet orange trees as source of inoculum, adults ACP were transferred to Rangpur lime seedlings for 21 days and after tested by PCR for Las and Lam. Both Lam and Las were detected by PCR in adult ACP after 1 hour AP (6.6%). For Las the efficiency of acquisition increased with the AP up to 7 days (16.6%) and decreased to 3.3% with 14 days AP. For Lam the efficiency of acquisition increased to 30% with 1 days AP and decreased after that to 3.3%. Inoculation Period for Las and Lam. Different inoculation periods (IP) were tested (30 min, 1h, 3h, 6h, 12h, 24h, 3 days, 7 days, 10 days and 14 days). Adults ACP had 21 days of AP in sweet orange as source of Las and Lam. After, they were put on test plants for different IPs. After 6 and 12 months, shoot samples were analyzed by PCR and all samples were negative for both Las and Lam. Exp. 3 ‘ Regardless the inoculation of trees at the screenhouses, some encaged trees showed symptoms just after building the screenhouses in December 2008 (probably they were already infected before be protected) and the severity progress of symptoms were assessed in those trees. About three year after that the average severity was 46.2 and 63.7%, respectively % for Hamlin/Rangpur lime planted in 1999 (6 trees) and planted in 2004 (2 trees). For Valencia/Rangpur lime planted in 1999 (5trees), the severity was 63.7% and for Pera/Rangpur lime planted in 2005 (1 tree) it was 37.5%. In the alternative experiment, comparing the disease severity on plants of Val’ncia/Swingle from January/March 2011 to January March 2012, the youngest trees (planted in 2007) showed the highest initial severity and also the highest final severity than older trees planted in 1999 and 1995. Comparing Valencia sweet orange at the same age but in different rootstocks, the severity increasing at the same period in trees grafted in Volkamerian lemon were double than in trees grafted in Swingle citrumelo. Comparing different scion varieties grafted on Swingle and at the same age, the severity increase were higher in Hamlin than in Valencia.
Immidicloprid applications and irrigation treatments started with the first spring flush on March 13, 2012 at the Southwest Florida Research and Education Center (SWFREC), of the University of Florida, in Immokalee, Collier County. The study will be conducted on citrus experimental groves, of Valencia orange of one and two years old, 5 to 6 years old and 8 to 10 years old. Field work will be timed with growth flushes in the spring and summer months. The soils in the SWFREC are poorly drained, with sandy textures, and they developed in ‘Flatwoods’ vegetation. Irrigation treatments were established 3 days prior to the initial application of Immidicloprid treatments and the Br tracer. The frequency of soil and leaf sampling were 3 times per week for two weeks following immidicloprid applications, twice per week for the next two weeks and then weekly for the remaining four weeks. A second application will be made with the next flush in mid May. The extraction procedures for immidicloprid in soil and leaf samples have been tested and will be used for samples now being taken. The analysis for soil degradation studies have not been completed, but will be available for the next report.
In the past quarter, we have identified four chemical compounds that Asian citrus psyllid antennae are capable of recognizing physiologically at the level of the antenna. Identification of two of these compounds was verified through the use of coupled gas chromatographic-electroantennogram detection (GC-EAD) and we as GC-mas spectroscopy. We believe, this is the first instance of successful electrophysiological recordings by the coupled GC-EAD method for any psyllid species. The four compounds are currently being tested in the laboratory in both Lake Alfred and Fort Pierce using olfactometers and in field trapping trials at both locations. Initial results suggest that these antennally active compounds may also elicit psyllid behavior, but are ongoing tests are focused on confirming this hypothesis. Our initial field test in February was inconclusive, because psyllid populations were low. Laboratory tests are ongoing and subsequent field testing is planned.
In this research, we have been developing a repellent formulation for Asian citrus psyllid (ACP). A DMDS-based SPLAT formulation has been developed. It is currently formulated and produced by ISCA technologies. Our recent results have produced inconsistent results; however, there have been cases where the formulation has effectively reduced psyllid populations both in Florida and in trials in another state. In the final year of the project, we have tested new active ingredients that may be more effective than DMDS for several reasons. First, these newly identified active ingredients are less noxious than DMDS and simply do not smell as bad to humans. This makes them much easier to work with. Also, these chemicals are less phytotoxic and easier to formulate. Therefore, these new formulations may not have the drawbacks that are associated with DMDS-SPLAT. In this previous quarter, we have been working to evaluate these new formulations and we have determined that two of the newly identified active ingredients are effective in repelling psyllids when deployed in SPLAT. We are currently finishing up these tests to hopefully determine whether a more practical SPLAT-based repellent formulation can be developed than our current DMDS-based standard.
Our studies from 2009-2011 have shown that ACP populations in Florida have developed varying levels of resistance to several insecticide chemistries. Baseline susceptibility data for both adult and immature ACP to commonly used insecticides was collected in 2009 and 2010. These data were collected for five ACP populations from various parts of Florida. In 2009, the highest level of resistance for adult ACP, as compared with the laboratory susceptible (LS) population, was found with imidacloprid with an LD50 resistance ratio (RR50) of 35 in one population. This was followed by chlorpyriphos (RR50 = 17.9, 13.3, 11.8 and 6.9), thiamethoxam (RR50 = 15 and 13), malathion (RR50 = 5.4 and 5.0) and fenpropathrin (RR50 = 4.8). In 2010, mortality of adults from all five sites sampled was lower than with the LS population at three diagnostic concentrations of each insecticide tested. Among nymph populations, indications of resistance were observed with carbaryl (RR50 = 2.9), chlorpyriphos (RR50 = 3.2), imidacloprid (RR50 = 2.3 and 3.9) and spinetoram (RR50 = 4.8 and 5.9). General esterase, glutathione S-transferase and monooxygenase levels were also elevated in field-collected adult and nymph ACP as compared with the LS population. Also, we tested whether changes in susceptibility of organophosphate and carbamate insecticides was due to target site (acetocholynesterate) inactivity. We proved that the levels of resistance we were observing were due to increased levels of detoxifying enzymes as opposed to target site insensitivity. In 2011, 3 diagnostic doses (LD50, LD75 and LD95), obtained using the laboratory susceptible population in 2009, were used to compare susceptibility levels among field-collected and laboratory populations. Susceptibility data obtained in 2011 show marked reduction in the susceptibility levels of ACP to chlorpyriphos and fenpropathrin, when compared to the susceptibility data obtained in 2010. Mean percent mortality obtained from all five locations was significantly lower than that of the laboratory susceptible population for all tested insecticides in 2011. Additionally, we have identified five CYP4 genes that were inducible with insecticide treatment in ACP. In 2011, gene expression analysis indicated significant overexpression of all CYP4 genes in field-collected populations when normalized against laboratory susceptible population. SDS-PAGE showed few differences in the total protein profiles among six populations, particularly for proteins of 25 and 200 kDa molecular masses. Western blot analysis indicated increased signal of a band corresponding to 60 kDa protein in Fort Pierce population when compared with the laboratory susceptible population. These results provide insight on the CYP4 mediated insecticide resistance in field populations of ACP, which has led us to study the effects of silencing such CYP4 genes in ACP through RNAi. Our preliminary results on RNAi show that silencing of CYP4 genes was achieved with as low as 25 ng dsRNA, which was confirmed through gene expression and western blot. The above results suggest that insecticide rotation that includes existing registered modes of action as well as incorporation of new modes of action or non neurotoxic products and molecular tools, such as RNAi could potentially be used to prolong resistance development in ACP. We have recently finished investigating various pesticide rotation modules in the field and we are currently analyzing those data. We are hoping to determine if there is an optimal strategy for rotating our currently available modes of action.
Low volume (2-10 gallons per acre) are currently routinely used by many Florida citrus growers. The cost savings as compared with standard higher volume applications (100-200 gallons/acre) make low volume applications a potential useful tool given the need for additional sprays that target Asian citrus psyllid (ACP). The objective of this investigation was to study potential alternative methods for implementing low volume technology, as well as, to understand the potential limitations of the technology. 1) Duration of residual toxicity. Insecticide residue on citrus leaves following applications may kill psyllids for up to several weeks. We investigated longevity of activity of low volume sprays, using leaves from field trials with fenopropathrin (16 oz/acre), phosmet (1.5 lb/acre) and imidacloprid (15 oz/acre) and compared with high volume applications. A bioassay was then performed with citrus leaf discs in a Petri dishes. Mortality was recorded at 24 h and 48 h intervals. The mortality of adult psyllids after 4 days was between 60 and 100% after high volume applications, but <10% after low volume applications. By day eight, only the high volume fenpropathrin treatment caused high mortality (80%). All other treatments tested showed <10% mortality. These results indicate very limited residual activity of low volume treatments. Essentially, the majority of psyllids are killed during the initial 24 hours following a low volume application and this is likely due to both fumigation and direct contact activity. 2) Border row treatment as a tactic for ACP management. The purpose of this study was to investigate the potential of border row treatments for psyllid management as compared with treating entire blocks with low volume sprays. Psyllid numbers in both fully and border only treated blocks were significantly reduced by the applications three and seven days after application. On day 14, the border row treatment was not different from the control, while psyllid populations were still reduced in the fully treated blocks. These results indicate that border row treatment by low volume may have some use for up to two weeks after treatment, but is not as effective as treating entire blocks of citrus at the five acre replicate plot sizes that we tested. These results indicate that border row applications of low volume sprays may be limited in effectiveness, but results may be different in larger-plot tests. 3) The vertical distribution of adult psyllids in mature citrus. Adult psyllid distribution within the canopy of citrus has has not been investigated thoroughly following applications of insecticides. Our season-long study revealed that there are up to three times more adult psyllids at ~3 m as compared with 1 m height within the canopy following insecticide treatment. Leaf disks from the top most leaves were previously shown not to be toxic to adult psyllids. A spray droplet penetration study was performed, using water sensitive paper (WSP) strips as an indicator. These strips were placed at three heights within the canopy of trees: 1.2, 2.1 and 3.2 m. Results revealed that droplets penetrated both sides of the leaf at 2.1 m only. At 1.2 m, only the upper surface received significant numbers of droplets. At 3.2 m, no droplets were detected. In summary the low volume technique results in lower penetration of the tree canopy as compared with high volume applications, which may in part explain the shorter longevity of efficacy of low volume applications as compared with standard sprays. Also, our tests indicated that adjuvants did not significantly improve longevity of effectiveness of our low volume applications.
Spatial and Temporal Incidence of Ca. Liberibacter in Citrus and Psyllids Detected Using Real Time PCR, January 2012. Objective 1. Assess seasonal patterns of pathogen incidence in citrus trees and psyllid vector populations in an infected experimental block. Since March 2008, the pathology and entomology researchers have been working at a site located within a commercial grove that initiated nutritional and/or insecticidal sprays on 7-year-old Valencia-on-Swingle trees. Initially, disease incidence of HLB in trees in the various plots average around 25%. One year later, disease incidence was greater than 80%, and in the nutritional treatment plots, 100%. Determining the titer of HLB in symptomatic leaf samples and in collected psyllids was possible by training and resources provided by collaborator, M. Keremane. Citrus leaf samples and psyllids, stored from initiation of the trial and sampled at approximately 6 month intervals, are being processed. Sampling continues on schedule, with processing and analysis remaining up-to-date. Data reveal that while some fluctuations in the titer of bacteria in occur at sampling dates, preliminary conclusions are limited. The data is skewed toward a detectable population of HLB by the selection of symptomatic tissue, therefore it may not be that differences in populations will be detected in symptomatic tissue. Other studies are using other sampling techniques to try to get around this bias. Objective 2. Evaluate the influence of cultural factors that affect incidence and titer of Liberibacter in citrus trees and psyllid populations including tree age, variety, rootstock, block size, surroundings and management practices such as vector control and tree removal. In another location where HLB incidence and tree health is being monitored on grapefruit and Hamlins receiving various treatments, including initially, tree removal, S. Halbert has been conducting trapping of psyllids. Psyllids from the traps are being analyzed for HLB titer by K. Hendricks, SWFREC. Four suction traps were operated at the SW Florida Research & Extension Center from July 2009 to present. These included an 8 meter tall trap and three 2 meter traps. Of the latter, one was in managed citrus, one was in unsprayed citrus, and the other was in an open field. Samples were collected approximately weekly. The psyllids were removed and identified in Gainesville. Beginning in 2011, all Diaphorina citri Kuwayama were tested singly for presence or absence of the HLB pathogen. All three short traps collected D. citri. Both traps located in citrus collected at least occasional D. citri throughout the year, but the trap in the unsprayed citrus collected the most. The trap in the open field showed peak activity in March, coinciding with the spring flush. These collections could indicate that longer distance flights away from the crop occur at that time of the year. Overall, there were five samples positive for Las and three questionable samples in 2011. There were positive samples collected from all three short traps. There was no difference in the numbers of positives by trap. This can be attributed to the fact that citrus greening disease is widespread and common in the Immokalee area. Preliminary data indicates that neither nutritional nor insecticidal sprays impacted the disease progress of HLB, because either the treatments were initiated during the long lag time between inoculation/symptom expression or another reason. Recent yield data indicates that trees in plot receiving nutritionals and insecticide are benefiting by increased yields.
Experiment 2 (within HLB-Area-Wide Management AWM). The incidence of HLB increased very few in the last 3 months during summer season (January to Masrch/12), in plots without insecticide application (from 7.3% in December/11 to 7.4% in March/12) and did not increased in plots with inseticide application (5.3%). Even during the summer, the ACP population density was very low (almost zero) and deccelerated in the last two years, even in the plots without ACP control. The paper “Efficacy area-wide of inoculum reduction and vector control on temporal progress of huanglongbing in young sweet orange plantings” by Bassanezi, R. B., Montesino, L. H., Gimenes-Fernandes, N., Yamamoto, P. T.; Gottwald, T. R., Amorim, L., and Bergamin Filho, A. were submitted to Plant Disease for publication. The full paper were sent to CRDF and the Abstract is: Huanglongbing (HLB), caused by Candidatus Liberibacter spp. and transmitted by the Asian citrus psyllid Diaphorina citri (ACP), is an important threat to citrus industries worldwide, causing significant yield loss. The current recommended strategies to manage HLB are to (i) eliminate HLB symptomatic trees to reduce sources of bacterial inoculum, and (ii) apply insecticides to reduce psyllid vector populations. The objective of this study was to assess the effectiveness and the importance of both strategies applied within young citrus plots (Local management), in different frequencies and combinations, on HLB temporal progress. Two factorial field experiments, E1 and E2, were initiated in a new plantation of sweet orange in a HLB epidemic region of Sao Paulo, Brazil, in October/05 and May/06, respectively. Local inoculum reduction levels for E1 were every 4, 8 and 16 weeks, and for E2, every 2, 4, 12, and 26 weeks. Local vector control levels for E1 were no control, program A (PA) and program B (PB), and for E2, no control and program C (PC), as follows. Psyllid control was done with two 56-day-interval soil or drench applications of systemic insecticides concurrently with the rainy season each year; and during the rest of the year, with insecticide sprays every 28 days for PA, and every 14 days for PB and PC. Regional HLB management was present for E1 and absent for E2. The beginning of the HLB epidemic was delayed for 10 months in E1, but wasn’t affected by different local strategies for both experiments. After 60 (E1) and 53 (E2) months, the HLB incidence and progress rates were not affected by different frequencies of local inoculum reduction in either experiment, and were different only in plots with and without local vector control in E2. In E1 the disease incidence was reduced by 90% and the disease progress rate by 50% in both plots with and without vector control. These reductions were explained by smaller psyllid populations and lower frequency of bacterialiferous psyllids in E1 compared to E2. Annual productivity remained increasing over time in E1 as expected for young plantings, whereas remained stable or decreased in E2. These results confirmed the great importance of primary infection by migrating bacterialiferous ACP populations on HLB epidemics and suggest that an area-wide inoculum and ACP management heavily affects HLB control.
During the past year, we have constructed four citrus tristeza virus (CTV) vectors containing four insecticidal peptides for management of the Asian citrus psyllid (ACP) and the brown citrus aphid (BCA). CTV expression vectors containing these peptides have been successfully bark flap-inoculated into plants to confirm systemic peptide expression and provide material for graft inoculation into citrus. To evaluate the effects of peptides on insect fitness, plants containing the CTV-expressed peptides have been used to graft-inoculated into citrus plants for psyllid bioassays. Since our last report, we have completed plant inoculations for each of the four CTV-peptide constructs originally proposed (henceforth A, B, C, and D). Most recently, fifteen plants have been grafted with peptide B and are being given latent period for the peptide to become established throughout the plants. The plants will be tested for the presence of CTV-peptide constructs using ELISA in a few days. Peptides C and D have been established in three and five plants, respectively, and additional plants will be grafted-inoculated to obtain a sufficient number of test plants for psyllid bioassays. Since the previous report, we have continued to conduct experiments to evaluate the lethal and sublethal effects of vector-expressed peptides A and B on development (egg and nymph), life history parameters (adult longevity, fecundity), and feeding of ACP and BCA. Bioassays with plants containing peptide A have been completed. Settling assays suggest that ACP adults prefer plants that do not contain either peptide A or B. Although adult survival was not significantly affected, development of eggs and nymphs were significantly longer when insects were exposed to plants containing peptide B compared with control plants. In addition, ACP feeding and fecundity were significantly reduced in the presence of peptide A compared with control plants. Similarly, the results of honeydew excretion assays suggest that peptide B reduces ACP feeding. In bioassays to evaluate the effect of peptides on BCA, survival of nymphs was significantly reduced when peptide A was present in citrus plants compared with control plants; however no other fitness parameters were significantly affected in response to peptide A. Longevity and fecundity of adult BCA were significantly reduced in response to peptide B plants compared with controls. The results from ACP and BCA bioassays with peptide B are based on four replicate plants only, due to limited availability of plants. Additional replications will be conducted as plants containing peptide B become available. Currently, artificial feeding bioassays are being conducted to evaluate the lethal concentration of a variety of insecticidal peptides, including the four originally proposed, against ACP. In addition, we have begun to conduct experiments to evaluate the effect of peptides on ACP endosymbionts, including Las. Insects from these ongoing bioassays are currently being collected and stored for subsequent analysis with qPCR analysis. In addition to the above ongoing experiments, our research plan for the next year is to conduct laboratory bioassays to evaluate the susceptibility of citrus leafminer, and T. radiata to citrus plants containing CTV-peptide constructs.
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. Following application of an LD80 dose (4 Jan), our colony experienced a crash. Because the untreated individuals were also affected, we are attributing this result to seasonal fluctuation of vigor. We are currently giving our murraya a 3-mo rest while we increase our laboratory psyllid populations. We continue to collaborate with the DPI CHRP program to evaluate results of the cooperative (area wide) ACP management program, in SW Florida (i.e. Gulf CHMA). We have presented this data for the last 10 cycles via interactive maps on our website (http://swfrec.ifas.ufl.edu/entomology/extension/chma/ for growers to use). These maps have allowed us to visualize ‘hot spots’ (i.e. those groves with high numbers of ACP for 3 consecutive cycles), and we are in the process of contacting growers to improve ACP management. 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. We have been using bucket pheromone traps dispensed in citrus groves and the slough to collect identifiable specimens for identification. Gracillariid leaf mining moths are very small, and often very difficult to identify solely based on morphology. We have used a combination of traditional morphological methods and COI barcoding, based on a mitochondrial DNA sequence. A sample of specimens that were collected with bucket traps was sent to the Lepidoptera sequencing lab of collaborator Kawahara at the McGuire Center for Lepidoptera and Biodiversity in Gainesville Florida for analysis. Thus far results show that there are many different Phyllocnistis species coming to the pheromone traps; P. citrella, P. insignis, P. vitegenella, and a newly discovered leafminer species to Florida. We have submitted grant applications for additional funding. We feel it would be beneficial to publish a paper that discusses genetic variation/species boundaries of Phyllocnistis found in our citrus groves and natural areas. 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 rear the parasitoid Citrastichus phyllocnistoides and support a program for monitoring CLM susceptibility to key insecticides. This summer we will use a diagnostic dose to monitor resistance in field populations of CLM exposed to intensive versus modest insecticide use.
Low volume (LV) aerial and ground sprays have become an important method of application in Florida citrus. Our eval- uations of LV application of 435 horticultural mineral oil (HMO) have shown promising results the last 3 years. Here we document overall results from the 5th trial begun Feb 2011 in a 10.9 acre plot of ‘Valencia’ orange in Lee County com- paring LV spray of 435 HMO with the Grower Standard (GS) and an Untreated check (UC). The grower has been applying a foliar nutritional program throughout the block. Three treatments were set out in 3×3 Latin square design. A Proptec rotary atomizer P400D spray machine was used for all treatments. HMO was applied alone (no water) every 2 wks at 2 gpa. Between Feb-Apr, 3 sprays of oil were applied, and the GS was Carbaryl and Azasol. Mean ACP counts were below the 0.2 adults/stem tap sample threshold in all treatments with no significant differences. Due to high freeze- induced fruit drop, harvest was early (Feb) and juice content averaged less than 50% (0.41). Total brix was within normal range of 9-14 for all samples, but the acid content was below 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 GS (12.6 lbs solids/tree followed by HMO (10.5) and UC (6.1). Between May-July, 7 sprays of HMO with Actara and Agri-mek for GS plots were applied. During May, significantly fewer psyllids were seen on GS trees than HMO trees, but during June these differences disappeared. We then added citrus leafminer (CLM) assessments to determine if treatments were effective at reducing CLM numbers. A damage assessment of leaves using a modified Horsfall-Barratt scale found significant differences between the GS and oil treatments, with the GS having less CLM damage. Between Aug-Oct, 5 sprays of HMO oil and 1 spray ea of Dimethoate and Delegate for GS were applied. Mean adult psyllid populations were lowest for GS, followed by Oil and UC. Thus, LV oil treatments were suppressing ACP, though not as effectively as the GS. From Nov 2011-Jan 2012, 3 sprays of HMO were applied, and all plots received a dormant spray of Danitol (Jan). Mean psyllid populations for GS and HMO treatments were significantly less than UC, with HMO treatments suppressing ACP as effectively as GS. Resets sampled in Oct for HLB and Ct titer showed no significant differences between treatments and low (< 3%) HLB incidence. CLM trap catches in Nov were significantly lower with HMO compared to GS and UC even though highest flush density was seen on HMO-treated trees. probably due to egg and larval mortality. Between Feb-Apr 2012, 4 HMO sprays and 1 GS of Micromite were applied. Mean ACP counts for GS and HMO were similar and lower than UC. Resets were sampled for % HLB, most samples were not usable due to frost damage. The 2nd harvest (27 Feb) showed HMO treatment with greatest lb solids followed by UC and GS. Acid/brix results are pending. CLM flight began early this year (2 Mar) with first peak at 16 Mar showing no significant differences between treatments. An experiment initiated spring 2011 on an 80ac block divided into 12 large plots in a RCBD with 4 treatments and 3 reps (Jul) evaluated aerial applications of Intrepid 2F, and Delegate. Significant control was obtained with the aerial application of Intrepid, but not as much or as enduring as with the ground application. An experiment initiated Feb 2011 compared LV (5 or 10 GPA - Proptec) vs. HV(40 or 120 GPA - Airblast) apps. of Movento SC along with Mustang Max 1.5 EC (5 gpa), Baythroid XL 1 EC (5 gpa) and Provado 1.6 F+Agrimek 0.15 EC (120 gpa). All treatments provided significant reduction in psyllid adults through 5 wks and nymphs through 4 wks except Mustang, low rate of Movento (5 gpa) and Provado + Agrimek.
we have completed the harvest for the fourth year of the Hamlin and Valencia trials with the Boyd Nutrient/SAR treatments. The ‘Hamlin’ orange block at SWFREC receiving the Boyd cocktail treatments was harvested in December before the freeze on January 4, 2011 with temperatures in Immokalee of 25 degrees F. Fruit yield on 8.2 foot tall trees from the better treatments averaged about 2+ boxes per tree. The better treatments contained Macro nutrients as DKP + KNO3, micro-nutrients Mg, Mn, Zn, Mo, B, and a Phosphite. Juice quality from the ‘Hamlin’ trees with HLB trial has not been affected. Citrus canker was a significant factor in our ‘Hamlin’ trial for the first time this year. Fruit loss due to canker varied from 40% in less vigorous trees to between 60% to 75% fruit loss in treatments stimulating more vigorous growth. Treatments with spray grade KNO3 + micro-nutrients had less fruit loss to canker. The less vigorous trees with less flush carried the larger fruit load with less fruit drop in the presence of citrus canker. Fruit yield from our 30 acre commercial ‘Valencia’ block experienced frozen fruit in the January freeze with some fruit loss, and still produced 1.6+ boxes per tree on 7 to 8 foot tall trees. This trial was harvested in March and juice quality data is not yet available. The highest yield per tree for ‘Hamlin’ and ‘Valencia’ 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. Treatment 3 (KNO3 + micro- nutrinets) has moved into the top three performers. 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 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. Psyllid populations for all treatments remained below the 0.20 threshold during each sampling period (13 Jan ‘ 21 Mar) except for 13 Jan when the nutritional only plots reached 0.23. Insecticide and Insecticide+nutritional had significantly (P< 0.05) fewer adult ACP than control or nutritional only on dates 13, 27 Jan; 10, 24 Feb; 7, 21 Mar. All three treatments had significantly (P < 0.05) fewer ACP than control on 21 Mar. Since our last report we applied a dormant spray of Danitol 4EC (12oz/ac) on 2 Feb in plots designated for insecticide treatment. Resets planted (June 2010) were tested for HLB detection (13 Jan) but showed no significant treatment effect on percent PCR positive for HLB (16% - 60% infection). All mature trees (10 years old) tested positive for HLB. Ct values were significantly less for Untreated (21.2) than the Insecticide only plots (22.5). However, there were no significant differences between the insecticide plus nutritional plots (21.6) and nutritional only plots (21.6). For the resets, there were no significant differences in Ct values (range 25.0 ' 33.4). All trees were harvested and all fruit weighed 8 Mar. Trees receiving the Insecticide + nutrition treatment produced greatest average yield (199.7 lbs/tree ' A) followed by nutritional only (182.3 - AB) Insecticide only (171.6 B) and Untreated (147.0 - C). We are waiting for results of brix/acid ratios.
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