This research seeks to determine whether young trees infected with CLas and displaying typical HLB symptoms can be brought to maturity and produce an economically viable yield. This will be achieved by managing a 58 acre grove of 3-year-old ‘Valencia’ / Kuharske Carrizo trees using a combination of three different foliar and three different ground applied nutritional programs. Factorial AxB treatments consist of A) ground-applied: 1) Liquid/dry+Ca (BHG standard), 2) Liquid+Ca, 3) Liquid/dry-Ca B) foliar-applied: 1) BHG standard-Ca, 2) BHG standard+Ca, 3) “Prescription”(+Ca). The prescription treatment was designed to be dynamic, customized for optimization, with feedback based on frequent leaf tissue analyses, visual symptoms, and the growth of the tree canopies and yield. There are six replications of treatments, with two being pure replications. Leaf samples were collected in August and December and the results of nutrient analysis of the leaf tissue are summarized below: *** August *** N is adequate P is OPTIMUM to high K is OPTIMUM Mg is OPTIMUM Ca is OPTIMUM for all treatments except low for the standard liq/dry treatment. S is OPTIMUM B is adequate but could probably use a boost for the spring bloom. Zn is OPTIMUM range on all treatments Mn is OPTIMUM for all treatments Fe is OPTIMUM for all treatments except low for the standard liq/dry treatment. Cu is above OPTIMUM to HIGH for all treatments *** December *** N is LOW to adequate P is OPTIMUM K is OPTIMUM Mg is OPTIMUM except LOW for the Ca foliar spray Ca is LOW for all treatments S is OPTIMUM B is LOW except for treatments receiving all liquid ground fertilizer Zn is just into the OPTIMUM range on all treatments Mn is OPTIMUM for all treatments Fe is LOW except OPTIMUM for treatments receiving all liquid ground fertilizer Cu is OPTIMUM to HIGH for all treatments
This research seeks to determine whether young trees infected with CLas and displaying typical HLB symptoms can be brought to maturity and produce an economically viable yield. This will be achieved by managing a 58 acre grove of 3-year-old ‘Valencia’ / Kuharske Carrizo trees using a combination of three different foliar and three different ground applied nutritional programs. Factorial AxB treatments consist of A) ground-applied: 1) Liquid/dry+Ca (BHG standard), 2) Liquid+Ca, 3) Liquid/dry-Ca B) foliar-applied: 1) BHG standard-Ca, 2) BHG standard+Ca, 3) “Prescription”(+Ca). The prescription treatment was designed to be dynamic, customized for optimization, with feedback based on frequent leaf tissue analyses, visual symptoms, and the growth of the tree canopies and yield. There are six replications of treatments, with two being pure replications. Following the March 2013 harvest and review of all the 2012/13 season data, the recommendations for the 2013/14 season should mainly involve any corrective action to avoid the possible detrimental effects of some foliar sprays on canopy growth, as evidenced by a suppression of canopy size and yield. Secondly, recent literature searches and discussions with other scientists have suggested that there may be some additional scope to mitigate HLB by adding plant growth regulators like 2,4-D to the foliar nutrient sprays. A very low but frequent dose of 2,4-D (a synthetic auxin hormone) mixed ONLY with the ‘prescription treatment’ is suggested. Using the CitrusFix formulation (40% w/v), a rate of 5 mL in 100 gal, producing 5.3 ppm a.i. is suggested for every spray that is applied from after 100% petal fall until winter. Leaf samples were collected in March 2013 and the results of nutrient analysis of the leaf tissue are summarized below: N is adequate P is OPTIMUM K is OPTIMUM except for one sample being lower Mg is OPTIMUM except for two samples slightly below optimum Ca is OPTIMUM for all treatments S is OPTIMUM B is adequate now and should be maintained Zn is OPTIMUM range on all treatments Mn is OPTIMUM for all treatments Fe is OPTIMUM for all treatments Cu is above OPTIMUM to HIGH for all treatments, particularly in the STD+Ca and the prescription foliar spray treatments It is evident after one year that the leaf tissue nutrient analyses are highly variable both spatially and temporally, and are also directly affected by growth rates of the trees. We are investigating the possible use of a real-time digital camera imaging system to periodically measure canopy color and other properties in the experiment plots. The unified expression of HLB and nutrient deficiency symptoms as chlorotic leaf colors may be useful for future interpretations and development of remedial actions.
This research seeks to determine whether young trees infected with CLas and displaying typical HLB symptoms can be brought to maturity and produce an economically viable yield. This will be achieved by managing a 58 acre grove of 3-year-old ‘Valencia’ / Kuharske Carrizo trees using a combination of three different foliar and three different ground applied nutritional programs. Factorial AxB treatments consist of A) ground-applied: 1) Liquid/dry+Ca (BHG standard), 2) Liquid+Ca, 3) Liquid/dry-Ca B) foliar-applied: 1) BHG standard-Ca, 2) BHG standard+Ca, 3) “Prescription”(+Ca). The prescription treatment was designed to be dynamic, customized for optimization, with feedback based on frequent leaf tissue analyses, visual symptoms, and the growth of the tree canopies and yield. There are six replications of treatments, with two being pure replications. In March 2013, the first fruit harvest of plots was conducted since the experiment was started in the previous spring of 2012. It was quite difficult to locate and photograph trees not showing any HLB symptoms, so it is safe to assume that infection levels are close to 100%. Despite the widespread HLB infection in the block, it was striking that most HLB-affected trees had over-wintered very well and had already produced a vigorous flush of new leaves. The bloom period was greatly prolonged due to the incessant flowering of HLB-symptomatic trees that have lost their normal synchronization of flowering with chill units, warming temperatures and increasing daylength. We were surprised that it was not possible to detect any differences between the appearance of trees during March 2013 in the different fertilization treatments, and that could be said for the entire growing season. There was evidence of mild to moderate preharvest fruit drop in the experiment, and that too could not be attributed to a treatment. In general, the trees in the experimental block looked good considering the HLB infection level. Average yield measured in all plots was 68 boxes/acre, which is well below average for fourth-year yield of ‘Valencia’. A possible remedy for boosting block yields when 100% HLB infection is expected as early as 2-3 years is to increase the planting density, (for example 151 to 242 trees/acre). The fruit yield was significantly higher for the foliar treatment excluding calcium (1). The cause of this yield difference was traced to the trees on that treatment having larger canopies than the trees receiving the Ca foliar sprays (2 + 3). Fruit size was unaffected, but fruit counts per tree were different, and furthermore, the fruit count per unit of canopy was the same, thus proving that the actual tree sizes were responsible for the differences in fruit yield per acre. A follow up investigation should examine the foliar sprays applied last year (2012) to see if there is a traceable component that could have caused foliage burn or similar damage to the +Ca treated trees. It seems unlikely that the Ca itself was responsible and likewise it seems unlikely that the ‘Ca treatment would have boosted growth more than the other treatments. It was noted that foliage copper levels were excessive, and higher in the +Ca foliar spray treatments (March leaf sampling). There were also a few significant differences in some of the juice quality parameters, and in general the values were fairly typical of young trees picked early in the season.
This research seeks to determine whether young trees infected with CLas and displaying typical HLB symptoms can be brought to maturity and produce an economically viable yield. This will be achieved by managing a 58 acre grove of 3-year-old ‘Valencia’ / Kuharske Carrizo trees using a combination of three different foliar and three different ground applied nutritional programs. Factorial AxB treatments consist of A) ground-applied: 1) Liquid/dry+Ca (BHG standard), 2) Liquid+Ca, 3) Liquid/dry-Ca B) foliar-applied: 1) BHG standard-Ca, 2) BHG standard+Ca, 3) “Prescription”(+Ca). The prescription treatment was designed to be dynamic, customized for optimization, with feedback based on frequent leaf tissue analyses, visual symptoms, and the growth of the tree canopies and yield. There are six replications of treatments, with two being pure replications. The grove continues to look good and actually improve, despite the nearly 100% HLB incidence. Foliation of canopies is dense, and leaf color through summer and into September was a healthy green, with vigorous new leaf flushes emerging frequently. Leaf samples were collected on September 10, 2013 and the results of nutrient analysis of the leaf tissue are summarized below: N is adequate P is OPTIMUM K is OPTIMUM Mg is OPTIMUM Ca is marginally low on the no-Ca soil treatment S is OPTIMUM B is OPTIMUM in most, but marginally low in the ‘Ca foliar treatment Zn is OPTIMUM on most, but marginally low for some foliar sprays with Ca Mn is OPTIMUM for all treatments but the same trend as for Zn was noticed: lower levels in the sprays with Ca Fe is low (<60) in some treatments Cu is OPTIMUM All the different fertilizer strategies chosen for testing in this block appear to be working equally well. There appear to be some adverse interactions of foliar calcium sprays with the other spray ingredients and / or the trees, as reflected in an altered nutrient concentration in the leaves. The block will produce a viable harvest although the fruit set should be better. Fruit sizing is normal as in healthy Valencia trees. Tree canopy sizes will be measured in November, to be reported in the next quarterly report.
July 2013 The objectives of this proposal are 1) to determine if a) leaf litter biodegradation treatments reduce Guignardia spp. pseudothecia and improve control afforded by routine fungicide applications; b) if biodegradation is affected by the current fungicide application practices; and c) whether the biodegradation treatments will affect current citrus best management practices (BMP); 2) to determine the seasonal dynamics of leaf litter inoculum load in varying management regime intensities and how environment affects pseudothecia production in the leaf litter; 3.) to test if the resistance to black spot in the leaves and fruit in sour orange is correlated and under simple genetic control through laboratory and field testing of progeny of sour orange crosses in both Florida and Australia. We are in the process of hiring some personnel for the project. Others have been hired and will be starting shortly. Small plots were set up an Immokalee area grove with 5% urea, CaCO3, Soil set, Compost Aid, Soil Set and Compost aid, and an untreated control. Leaves were collected and treated. The samples were collected and are being processed. To look at the effect of bagasse, the Senior Biological Scientist and the post doctoral associate worked on assembling the necessary supplies and components to carry out the controlled experiment portion of this project. This involves an in vitro study of the decomposition of citrus leaves and inactivation of G. citricarpa by various amendments including bagasse. A microbial consortium of fungal and bacterial strains to aid in the decomposition of bagasse and of citrus leaves was identified. Cultures of these microbes were obtained and are stored in our laboratory. Delivery of the bagasse for the controlled experiment was arranged and scheduled. Future availability of bagasse for the controlled experiment as well as for the field experiment was confirmed. Sources for field soil and both healthy and infected citrus leaves were found. Available lab facilities to house the controlled experiment were confirmed. A laboratory on the UF campus was identified that could perform the leaf tissue, fiber, nitrogen and carbon analysis. This analysis will be used to monitor leaf litter and bagasse decomposition. Construction of the plastic boxes with spore traps is currently in the planning stage. State regulations for working with Guignardia citricarpa were discussed with Tim Schubert at the Division of Plant Industry. There are reports of significant resistance to black spot in sour orange types, most notably ‘Chinotto’. The USHRL scion breeding program has a large population of seedlings from crosses between ‘Chinotto’ and the USDA mandarin hybrid selection 1-37-12, which are now fruiting, and have been evaluated for a number of fruit characteristics. Some of these approach commercial fruit quality and it is reasonable to expect that this population may be segregating for resistance to black spot. Ten seedlings of each of 20 selected Chinotto x 1-37-12 hybrids, the two parent genotypes, and the susceptible standard ‘Valencia’ have been developed at the USHRL and are ready for trial exposed to black spot inoculum. The subcontracting process with the University of Queensland is still underway.
July 2013 The objectives of this proposal are 1) Determine the base line level of Guignardia citricarpa sensitivity to fungicides registered for disease control in citrus and evaluate new products for efficacy against G. citricarpa in vitro; 2) Conduct and improve implementation of spray trials for efficacy of registered products for citrus and to evaluate novel compounds in the field; 3) Optimize field evaluation of control measures through analysis of the spatiotemporal disease progress utilizing past and current field data of the outbreaks to gain knowledge on the incidence, severity and rate of the epidemic and assess the fungal population to increase the likelihood of successful field research and 4) Evaluate products and treatment conditions for postharvest control of citrus black spot. This quarter we accomplished: Objective 1: Isolates were single spored in preparation for the in vitro experiments. Preliminary data on tetraconazole and propiconazole, two unregister demethylation inhibition fungicides was collected to determine the optimal dosages to use. So far 36 isolates have been used for the effective concentration calculations. The preliminary experiments for difenoconazole and fenbuconazole have been initiated. Objective 2: The field trial was established in a commercial grove that was identified with ‘Valencia’ fruit with black spot. In spring 2013, the site was was scouted and rows of ‘Valencia’ were identified that had fairly even distribution of fruit with symptoms of black spot. Plots contained three trees with at least two trees serving as buffers between each plot. There were four replications per treatment arranged in a randomized complete block design. Sprays were initiated in May after fruit harvest. Applications were applied with an Air blast sprayer calibrated to deliver 126 gal per A operating at 200 psi and 3 mph with a 25 gallon mix. Objective 3: We are currently looking for suitable sites to conduct the spatial studies. This study will begin in earnest close to fruit maturity when symptoms become apparent. Objective 4: An experiment to determine if thiabendazole, imazalil, SOPP (2%), graduate A+, salicylic acid and chitosan produced either an inhibition zone of conidia germination or reduced mycelia growth measurements was initiated but is currently on-going. An experiment to look at the heat tolerance of conidia, plates were held at 50, 35 or 20C for 5 days. After 5 additional days, at 20C growth was observed on the 20C treatment plates but not 35 or 50C. After 10 days there was sporadic growth at 35C but still nothing at 50C.
June 30, 2013 The objective of this project was to investigate three questions: 1) what is the seasonal pattern of Ca. Liberibacter asiaticus (Las) prevalence in leaf tissue on a grove scale; 2) what are the flushing patterns of citrus and do the flushing patterns affect the prevalence of Las in Diaphorina citri or citrus leaves; and 3) what is the prevalence of Diaphorina citri carrying Las on a grove scale and how does it compare the results from the citrus trees in the same grove. In 2008 and 2009 Ebert and Rogers demonstrated that the prevalence of Las in the Asian citrus psyllid (ACP) varied seasonally but the pattern between seasons was not consistent. It was suggested that perhaps the reason for the differences between the years related to the flushing patterns of citrus and the prevalence of the bacterium in the leaves where ACPs are feeding. This project aims to determine if there is a relationship between the frequency of disease on branches and ACPs. Sample collection of psyllids, phenology and plants has continued through the spring and summer. More Psyllids have been collected from 2 sites but remain elusive at the 3rd site. At the most severely affected site, the trees have begun to decline considerably and are not flushing frequently. Plant and psyllid samples have begun to be extracted again. PCR has begun to calculate the pool size for the remaining samples. This will help to clear the back log of samples and get the project back on track.
June 30, 2013 The objective of this project was to investigate three questions: 1) How long does a leaf needs to be infected by Guignardia citricarpa before ascospore production can be initiated; 2) How does infection and colonization of leaves by Guignardia citricarpa occur and potentially showing how pseudothecia, the sexual spore producing structures, are produced; and 3) what is the interaction between the common twig colonizing pathogen Diaporthe citri and the black spot pathogen Guignardia citricarpa and whether they can co-exist to successfully sporulate on dead twigs. Guignardia mangiferae sequencing is complete and the assembly has begun. The quality of the sequence is better and we are considering resequencing G. citricarpa. The full mating type gene has been located and the information will be used to better characterize the mating gene from G. citricarpa which appears to be missing a section. Since the GFP labeled strain, does not reliably retain the gpf gene, we have started greenhouse experiments using sectioning to locate and follow G. citricarpa in the leaf. We continue to work with the gfp labelled strains but will not rely on the labeling for the experiments.
We have constructed artificial mirco RNA interfering RNAs and are evaluating them as a strategy to deliver specific anti-psyllid RNAs to psyllid targets. Our belief is that these will be highly specific, and we know that miRNAs traffic in the phloem so should be available for phloem-feeding hemipterans such as psyllids. Seven amiRNAs targeting BC-ATPase were made and cloned into pBluescript SK, which are pAMIRA1, pAMIRA1c, pAMIRA2, pAMIRA2c, pAMIRA3, pAMIRA3c, and pAMIRA2PE. Four amiRNAs targeting GFP were made and cloned into pBluescript SK as well, which are pAMIRG1, pAMIRG1c, pAMIRG2, and pAMIRG2c. All 11 amiRNAs were then cloned into pGWB2, a gateway binary vector for expression driven by 35S promoter and into a viral vector with one extra stemloop from amiRA2 for amiRNAs of BC-ATPase and extra stemloops from amiRG1 and G2 for amiRNAs of GFP. The viral vector carrying amiRNAs were cloned into binary vector pCB301. We know that we can test RNA constructs on D. citri by in vitro feeding, but our hope is to also transiently express interfering RNAs in citrus such that they can move in the phloem and be acquired by feeding D. citri. We are utilizing a variety of approaches to test this possibility. So far we have performed agroinfiltration experiments on citrus and tobacco plants (the latter for the potato psyllid, Bactericera cockerelli). We used 35S promoter driven constructs and plant viruses in attempts to achieve gene expression. GFP assays failed to show detectable fluorescence in 5 different citrus types, but high level GFP expression was seen in tobacco.
We have constructed artificial mirco RNA interfering RNAs and are evaluating them as a strategy to deliver specific anti-psyllid RNAs to psyllid targets. Our belief is that these will be highly specific, and we know that miRNAs traffic in the phloem so should be available for phloem-feeding hemipterans such as psyllids. Seven amiRNAs targeting BC-ATPase were made and cloned into pBluescript SK, which are pAMIRA1, pAMIRA1c, pAMIRA2, pAMIRA2c, pAMIRA3, pAMIRA3c, and pAMIRA2PE. Four amiRNAs targeting GFP were made and cloned into pBluescript SK as well, which are pAMIRG1, pAMIRG1c, pAMIRG2, and pAMIRG2c. All 11 amiRNAs were then cloned into pGWB2, a gateway binary vector for expression driven by 35S promoter and into a viral vector with one extra stemloop from amiRA2 for amiRNAs of BC-ATPase and extra stemloops from amiRG1 and G2 for amiRNAs of GFP. The viral vector carrying amiRNAs were cloned into binary vector pCB301. We know that we can test RNA constructs on D. citri by in vitro feeding, but our hope is to also transiently express interfering RNAs in citrus such that they can move in the phloem and be acquired by feeding D. citri. We are utilizing a variety of approaches to test this possibility. So far we have performed agroinfiltration experiments on citrus and tobacco plants (the latter for the potato psyllid, Bactericera cockerelli). We used 35S promoter driven constructs and plant viruses in attempts to achieve gene expression. GFP assays failed to show detectable fluorescence in 5 different citrus types, but high level GFP expression was seen in tobacco.
We have previously shown that citrus engineered to produce dsRNA’s, matching the sequence of a specific Asian citrus psyllid (ACP) mRNA, induced ACP mortality when adult ACP fed on these plants. We have also shown that when psyllids containing the bacterium that causes citrus greening (Candidatus Liberibacter asiaticus,CLas) are fed on these plants for 10-15 days, the CLas is no longer detected in the psyllids. Furthermore, none of the nymphs hatched from eggs laid by CLas-containing psyllids contain CLas if fed on the dsRNA producing citrus. Replications of these experiments have been conducted during this reporting period. Furthermore, this research was now expanded to understand the molecular response occurring within the ACP as a result of specific dsRNA ingested. This was performed by conducting RNAseq analysis of the transcripts isolated from ACP that have fed on the specific dsRNAs. These experiments have been conducted and RNAseq data has been generated and is now being analyzed.
Incidence of citrus canker has been increasing in Florida due in part to increased pressure from citrus leafminer (CLM). It is likely that broad-spectrum insecticides for ACP management have impacted natural enemies of CLM leading to its rebound as a pest. The objectives of this study are: (1) Assess the use of pheromone traps for monitoring CLM populations, and development of a preliminary degree-day model, (2) evaluate effectiveness of early season and aerial applications to reduce CLM and canker, (3). Obtain baseline susceptibility to key insecticides, and (4) Use a diagnostic dose to monitor resistance in field populations of CLM exposed to intensive versus modest insecticide use. Objective 1: We have been monitoring adult CLM weekly using delta pheromone traps in 3 commercial groves under different management scenarios: Grove 1) sprayed at peak trap capture using different trap densities, Grove 2) sprayed based an ACP threshold or biweekly low volume (LV) sprays of horticultural spray oil (HMO), and Grove 3) sprayed at threshold or untreated. CLM damage is being assessed using a modified Horsfall-Barratt scale 1 to 8 and canker by percent incidence for individual trees, number of areas or ‘hits’ present in a tree, and proportion of diseased fruit. In May, leafminer damage and canker assessments resumed for 2013. Pheromone traps were deployed in citrus groves and non-citrus areas (OK Slough, 2011, 2012, 2013) to determine density of non-target species captured by the CLM lure. At this time, specimens are still being dissected for species identification. Canker and leaf damage assessments for spring were completed in May for four commercial groves, and data entry is pending. Likewise, pheromone trap data for May, June, and July are still in process of being counted and recorded. Four phenology models (206 degree days, 238dd, 265dd, and 398dd) are currently being analyzed for the best fit with Florida moth flight. Models were compared by looking at the differences in degree days between estimated model peak flight (50% generation time) and peak CLM flight of moth catch. The smallest difference in degree days between model and CLM peak flight represents the best fit. Thus far, there is no significant difference between models 206, 265, and 398dd, but least difference was seen comparing capture data from mature trees to predictions of the the 206 dd model whereas the 265dd model fit best with data from a grove with 10% resets. We are looking into the association with flush, and it appears both models may need to be further tested for another year. Objective 2: A 130-ac experimental block (Grove 4) divided into 4 replicated treatments: 1) Delegate applied early, 2) Delegate applied late, 3) Sprays following peak CLM flight, and 4) Rotations of OPs and pyrethroids. Delegate was applied early on 16 Apr at 4oz/ac with 2% v/v 435 citrus oil @ 90 gpa. On 29 Apr, 3lbs of copper, Dimethoate 1.5 pints (peak flight only plots), and Movento 16 fl oz (on Grower Standard and Delegate Late plots). Delegate Late will be sprayed in a couple of weeks Application in the peak-sprayed plots are finished this year, and their effect on late summer, fall CLM damage will help determine if just two precisely planned peak sprays are effective at controlling CLM the remainder of the year.
Citrus leafminer (CLM) is a major pest of citrus, causing direct damage and increased incidence/intensity of citrus canker. Pheromone traps are useful for monitoring CLM populations and may catch thousands of moths per week. However, there is a lack of information on effective range of the traps which compromises their usefulness. Moreover, we have preliminary results showing that at least 3 other leafminer species are also captured, including Phyllocnisitis insignis, P. vigitegenella, and an unknown new species. Objectives of the proposed project are: (1) evaluate the effective range of standard delta sticky traps armed with CLM pheromone, (2) assess species composition of trap catches within and at defined distances from citrus groves, (3) calibrate traps with direct assessment of damage and canker incidence/intensity as tools to monitor success of CLM management programs, and (4) provide an analysis of the economic benefit of CLM management in citrus cultivars over a range of canker susceptibility. Funds for this grant were received on 5/10. Objective 1: Lure Degradation Study for Spring 2013 began on 20 May: Delta pheromone traps (ISCA) were dispersed in a 39ac block of Pineapple orange at Duda & Sons, Inc. located in Hendry County, Florida. Tree spacing is 12 x 25 feet with 24 plots (1.63ac each). Two commercial lures were tested 1) Alpha Scents (A) lure, and 2) ISCA (I) lure. Pheromone traps were dispensed at ~1ac positions at central locations in plots and data collected at 1 week intervals for comparison of trap catch. Traps with lures changed on a weekly basis served as a positive control. Trap durations throughout the block were random with 3 replicates. Four days after traps were dispensed, all aged traps for brand A caught the same number of moths as control, however, aged brand I traps all caught significantly fewer moths than the positive control. There were no significant differences between moth catches from traps aged 4 or 8 weeks. At 9 days no significant difference was observed in number of moths captured among the positive control for Brand A or brand I aged 4 or 6 weeks. Likewise, no significant difference at 14 days in moth catch amoung all traps of the A brand, whereas only week 4 of the I brand was similar to the positive control. At 30 days, aged I traps were significantly different than the positive control, while 4 and 8 week A traps were still catching moths similar to a new lure. Hence, during spring lures of either brand remained effective for up to 12 weeks. Lures are currently being aged for Fall 2013 efficacy testing. At with next peak flight we will start the mark and re-capture experiments. Objective 2: Bucket traps in the OK slough were re-armed with kill strips and lures on 28 June. Moths will be collected this week, separated by morph, and submitted for PCR testing for species identification in Gainesville. Objective 3: Bucket traps were dispensed 28 June, at a density of 1 per treatment plot in a commercial grove where we have been conducting a nutritional trial the past 5 years. Moths will be collected this week, separated by morph, and samples sent to Gainesville for species identification by bar-coding. In this grove, we have historically noted two species of moth captured. These results will help us correlate the true percentage of CLM present , its associated leaf damage and canker presence, and perhaps determine an economic threshold.
We have previously shown that citrus engineered to produce dsRNA’s, matching the sequence of a specific Asian citrus psyllid (ACP) mRNA, induced ACP mortality when adult ACP fed on these plants. We have also shown that when psyllids containing the bacterium that causes citrus greening (Candidatus Liberibacter asiaticus,CLas) are fed on these plants for 10-15 days, the CLas is no longer detected in the psyllids. Furthermore, none of the nymphs hatched from eggs laid by CLas-containing psyllids contain CLas if fed on the dsRNA producing citrus. Replications of these experiments have been conducted during this reporting period. Furthermore, this research was now expanded to understand the molecular response occurring within the ACP as a result of specific dsRNA ingested. This was performed by conducting RNAseq analysis of the transcripts isolated from ACP that have fed on the specific dsRNAs. These experiments have been conducted and RNAseq data has been generated and is now being analyzed.
This project evaluates the impact of psyllid control programs on non-target pests, beneficial insects and mites. Two large replicated blocks of mature citrus in two conventional groves of Hendry County and one each in Collier and Lee counties untreated or treated with foliar sprays of insecticides, horticultural oils, and nutritionals were sampled for ACP, citrus leafminer (CLM), citrus rust mites (CRM), citrus red mite, predatory mites, snow scale, chaff scale, Glover scale, purple scale, citrus blackflies, whiteflies, mealy bugs, as well as their natural enemies and fruit damage. The calendar and 0.2 ACP adults per tap sample threshold treatments in the block of ‘Early Gold’ in Hendry county, received Micromite 6.25 oz/ac + 435 oil (2%) on 29 April and Delegate 4.5 oz/ac + 435 oil (2%) on 11 June. In ‘Valencia’ block, calendar treatment received Danitol at 16 oz/ ac on 8 April, Micromite 6.25 oz/ac + 435 oil (2%) on 29 April and Delegate 4.5 oz/ac + 435 oil (2%) on 11 June. The treatment with threshold of 0.2 adults per tap sample also received applications of 8 April and 11 June and 0.7 adults per tap sample threshold received 8 April application only. All treatments received a nutritional spray on 9 April. These treatments provided significant suppression of ACP. In May, CRM averaged 0.01 and 0.59 per lens field (LF) in calendar and 0.2 ACP threshold treatments in ‘Early Gold’, respectively, significantly less than 3.4 per LF in untreated or 11.4 per LF in 0.7 ACP threshold treatment which also remained untreated, indicating that Micromite controlled both ACP and CRM. CRM populations were down in June averaging ‘ 2.7 per LF and no significant effect of Delegate observed. In ‘Valencia’ CRM averaged 1-3 per LF in April and there was no significant effect of Danitol. In May or June, CRM dropped to ‘ 0.3 with no effect of Micromite or Delegate observed. Predatory mites averaged ‘ 0.1 per LF in both blocks during three months and did not differ across treatments. Voliam Flexi at 7oz/ac applied to insecticide treatments suppressed ACP in a block of ‘Valencia’ in Collier county where insecticides, insecticides + foliar nutrition, nutrition only and untreated are being compared against ACP. CRM averaged ‘ 0.6 per LF, not signifcantly different between treatments but seen mostly in nutritional and untreated plots except June. Predatory mites did not differ between treatments in April or May but averaged 0.4 per LF in the insecticide only treatment in June significantly more than ‘ 0.05 per LF in the remaining treatments. Low ACE populations in a block of ‘Valencia’ orange in Lee county were compared among treatment with biweekly applications of 435 oil, a grower standard that did not require insecticides and an untreated check. CRM average dropped from 4.2 per LF in April to 0 per LF in June in the untreated plots with no significant difference observed between treatments. Predatory mites averaged ‘ 0.08 per LF again with no differences among treatments. A manuscript entitled ‘Microbial and Synthetic Insecticidal Sprays for Asian Citrus Psyllid and Citrus Leafminer Control in Oranges’ was presented at the annual meeting of the Florida State Horticultural Society and submitted for publication. Studies concluded that synthetic insecticides provided more psyllid reduction than microbials, and reduced leafminer for up to 17 days. New products tested and in the registration process for use on citrus will extend the range of tools available to control these pests. While the effectiveness of microbial and oil sprays tended to be short lived, they could still be useful to conserve natural enemies, for application on blooming citrus and in organic groves which prohibit synthetic products.
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