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United States Department of Agriculture

Agricultural Research Service


Location: Subtropical Insects and Horticulture Research

2010 Annual Report

1a.Objectives (from AD-416)
To characterize plant responses to feeding by horticultural pests, identify sources and genetic mechanisms of plant resistance to subtropical pests, and select resistant germplasm. To develop and implement biological control programs that reduce the economic importance of subtropical pests of horticultural crops. To increase our knowledge of salient aspects of the biology and behavior of invasive horticultural pests in association with their host plants and natural enemies. Identify combinations of pest control tactics for pests of floricultural and nursery/landscape plants that interact synergistically to improve pest control, are practical to implement, and will minimize environmental disruption.

1b.Approach (from AD-416)
IPM strategies based on biological control will be developed. Natural control of subtropical insect pests by native and imported biological control agents will be assessed, and methods of conservation and augmentation to boost natural control by these agents will be investigated. Exotic biological control agents for invasive insect pests will be identified through literature reviews, collaborations with foreign scientists, or foreign exploration; adhering to federal and state regulations, these agents will be imported into the US, evaluated under federal or state quarantine facilities, released and monitored for establishment and impact. IPM strategies based on plant resistance will be developed. Insect bioassays and field trials will be conducted to identify plant varieties that are pest resistant. Citrus, vegetable and ornamental germplasm as well as non-host plant species will be screened; genes associated with insect resistance will be cloned, characterized and considered for cultivar improvement through traditional and transgenic procedures. When plant resistance is found, plant products responsible for resistance will be identified and explored for use in IPM. Transgenic plants produced at USHRL or elsewhere will be evaluated for effects on insect biology, resistance to pests, and disease transmission by insect vectors. The genetic bases of insect biology and of interactions among insect vectors, plant pathogens and host plants will be investigated using molecular techniques and genomics analyses, and IPM opportunities based on these investigations will be pursued. Molecular techniques will be used to examine the biology, gene expression and biochemical pathways of exotic insect pests. Vector-pathogen relations will be characterized biochemically and biologically, and the results will be applied to insect pest problems. Research on insect biology and behavior will be conducted to advance IPM. Biorationals such as entomopathogenic fungi, viruses and bacteria, microbials, sugar esters, oils, and azadiractin that have potential as environmentally benign IPM components will be identified and assessed. Methods of monitoring and estimating infestation densities of insect pests and their natural enemies will be developed including traps baited with attractants and sampling protocols. The ecology of insect pests and their natural enemies will be assessed in relation to pest management.

3.Progress Report
Research on Diaprepes root weevil continued to identify attractants from host plants and conspecifics. A putative pheromone has been identified. We expanded the search for host plant attractants and have identified one new plant volatile that consistently elicits antennal response.

Methods for detecting, monitoring and managing citrus leafminer using a synthetic sex pheromone continued. An artificial diet and feeding arena was developed for adult Asian citrus psyllid. Artificial diet was successfully used to identify toxic proteins and RNAi molecules that have the potential for use in novel Asian citrus psyllid control strategies.

Studies on the Asian citrus psyllid (ACP) led to the identification of molecules that inhibit the production of psyllid salivary sheaths during the feeding process.

Research on flight activity of the Asian citrus psyllid (ACP) revealed that the psyllid routinely disperses to and from citrus trees at distances of up to 500 feet, with consistent flight activity distant to citrus occurring in spring.

Progress was made in the area of detecting and estimating Asian citrus psyllid (ACP) population levels using traps and a tap-sampling protocol.

The Asian citrus psyllid (ACP) was shown to be cold hardy enough to indicate that large numbers of the psyllid would have survived all freezes that have occurred in the past in citrus from north central to southern Florida.

Research was initiated on finding genotypes of citrus and its relatives that exhibit resistance to infestations of Asian citrus psyllid (ACP).

Tamarixia radiata, a parasite of Asian citrus psyllid, was found to be highly susceptible to several pesticides commonly used in Florida citrus.

A phylogenetics analysis of different geographical populations of Tamarixia radiata revealed genetic differences, which might explain why the parasitoid exerts higher levels of biological control in some locations than others.

The relative titer of the huanglongbing bacterium varied among alimentary canal, salivary glands and other organs of its vector, the Asian citrus psyllid.

Research was initiated to sequence the entire genome of the Asian citrus psyllid (ACP).

Research in Florida documented that injury by the citrus leafminer to citrus leaves exacerbates the incidence and severity of citrus canker disease.

BMPs (Best Management Practices) for controlling whitefly biotypes were evaluated in the greenhouse.

Ornamental pepper continues to be evaluated for a banker plant system for the predatory mite, Amblyseius swirskii.

A thrips management program for plants for planting was developed and is available through the chilli thrips website for immediate distribution of efficacy results and information especially pertaining to chilli thrips but other species of thrips as well.

The fig whitefly is a recent invasive species that has become a major pest. A pilot study showed that a both a biopesticide (PFR 97) and a neonicotinoid insecticide were compatible with enzootic entomopathogenic fungi and natural enemies for managing the fig whitefly.

This project has been replaced by bridging project #6618-22000-037-00D pending review.

1. ARS entomologists at Fort Pierce, Florida collaborated with the University of Florida and private industry to develop two new products based on insect pheromones to control the citrus leafminer and citrus canker. A third company, International Fly Masters, Inc., is collaborating with ARS on a novel application technology for these and other semiochemical-based products. ARS research identified optimal blends of pheromone compounds for these products, determined optimal distribution of product in citrus groves, and is developing application technology for efficient and economical delivery of these products to the field. These products are expected to contribute to reduced loss to leafminer damage, reduced incidence and severity of citrus canker, and reduced use of traditional hard pesticides. Of equal importance is the application technology because of its immediate application in citrus and specialty crops (e.g., grapes) and for semiochemicals that target other important pests as they become available.

2. Detection methods and sampling protocols for Asian citrus psyllid (ACP) were advanced by ARS researchers in Fort Pierce, Florida. The need for psyllid detection tools in areas being monitored for a psyllid invasion continued this year in California and Arizona. Yellow sticky traps were more effective than stem tap samples for detecting adult psyllids when populations were scarce. There were no advantages among yellow, green or lime green sticky traps in detecting psyllids when populations were scarce. Growers interested in utilizing spray thresholds for the psyllid, or comparing infestation levels of psyllids in different groups of citrus trees, need a reliable sampling protocol to estimate densities. A stem-tap sampling protocol was developed that provided estimates of an adequate precision level at means of one or more psyllids per sample.

3. The chemical structure of a putative pheromone isolated from adult males of the Diaprepes root weevil was determined by ARS scientists in Fort Pierce, Florida in collaboration with ARS, CMAVE, Gainesville, FL. The structure represents a novel compound. Chemical synthesis was accomplished by an ARS collaborator at Beltsville, MD. To date, we have been unable to confirm activity by GC-EAD (Gas Chromatography Electroantennographic detection) suggesting that enantiomeric impurities may inhibit antennal response. Software and hardware problems with GC-EAD systems have been largely solved; two GC-EAD systems are now operational at USHRL.

4. A novel deployment device for applying semiochemical-based products to specialty crops was developed and successfully tested in the field by ARS researchers in Fort Pierce, Florida. The device consisted of two disks connected by string. Each disk was loaded with a wax slow release matrix (SPLAT which is a Specialized pheromone and lure application technology), ISCA Technologies, Riverside, California, a private corporation) containing the sex pheromone of the citrus leafminer. The device proved effective at becoming securely entangled in tree branches and effectively delivered pheromone-loaded SPLAT that resulted in disruption of trap catch of male P. citrella.

5. Research by ARS researchers in Fort Pierce, Florida on novel approaches to control the Asian citrus psyllid has identified the formation of psyllid salivary sheaths during the feeding process as a key interdiction point. A method of purifying secreted salivary sheaths has been developed and compositional studies of these sheaths has led to the identification of chemicals that can inhibit their formation. Because these salivary sheaths are an integral part of the feeding process, blocking their formation should result in their inability to feed on the plant phloem. This finding has led to a three year grant for $483,000 by the Florida Citrus Research and Development Foundation.

6. Because controlling the Asian citrus psyllid is key to the prevention of the spread citrus greening disease, identification of methods to produce citrus that are resistant to psyllid feeding is of high priority. In this direction researchers with ARS in Fort Pierce have discovered proteins and RNAi molecules that cause increased mortality in psyllids when fed in an artificial diet system. These results have led to strategies that are now being employed to create transgenic citrus expressing these chemicals in hopes of creating psyllid resistant citrus varieties.

Review Publications
Hunter, W.B., Shelby, K., Boykin, L.M., Dang, P.M., Weathersbee III, A.A. 2009. Ribosomal proteins and expressed sequence tags from Lysiphlebus testaceipes (Hymenoptera: Aphidiidae). Florida Scientist. 72(3):196-207.

Avery, P.B., Hunter, W.B., Hall, D.G., Jackson, M.A., Powell, C.A., Rogers, M.E. 2009. Diaphorina citri (Hemiptera: Psyllidae) infection and dissemination of the entomopathogenic fungus Isaria fumosorosea (Hypocreales: Cordycipitaceae) under laboratory conditions. Florida Entomologist. 92(4):608-618.

McKenzie, C.L., Shatters, Jr., R.G. 2009. First report of "Candidatus Liberibacter psyllaurous" associated with psyllid yellows of tomato in Colorado. Plant Disease 93(10):1074.

Barr, N., Hall, D.G., Weathersbee, A.A., Nguyen, R., Stansly, P., Oureshi, A., Flores, D. 2009. Comparison of laboratory colonies and field populations of Tamarixia radiata, an ecto-parasitoid of the Asian citrus psyllid, using internal transcribed spacer and cytochrome oxidase subunit l DNA sequences. Journal of Economic Entomology. 102(6):2325-2332.

Stelinski, L., Lapointe, S.L., Meyer, W.L. 2009. Season-long mating disruption of citrus leafminer, Phyllocnistis citrella Stainton, with an emulsified wax formulation of pheromone. Journal of Applied Entomology. 134: 512-520.

Lapointe, S.L., Niedz, R.P., Evens, T.J. 2010. An artificial diet for Diaprepes abbreviatus optimized for larval survival. Florida Entomologist. 93: 56-62.

Lapointe, S.L., Evens, T.J., Niedz, R.P., Hall, D.G. 2010. Artificial diet optimized to produce normative adults of Diaprepes abbreviatus (Coleoptera: Curculionidae). Environmental Entomology. 39:670-677.

Last Modified: 4/19/2014
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