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United States Department of Agriculture

Agricultural Research Service


Location: Subtropical Insects and Horticulture Research

2008 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
Relates to National Program 304 Crop Protection and Quarantine, Components IIa Basic Biology, IIb Rearing of Insects and Mites, IIIa Understanding the Complex Interactions, IIIb Population Studies/Ecology, Va Traditional Biological Control, Vb Breeding for Host Plant Resistance, Vd Other Biologically-Based Control, and VIa Sampling Methods, Detection and Monitoring. Seasonal ecology of pink hibiscus mealybug was clarified using traps baited with a new synthetic sex pheromone. Advances were made in biological control of Diaprepes root weevil. Two Caribbean parasitoid species are now established in south Florida. Releases of one parasite species were initiated in Texas. The physiological and developmental responses of each life stage of Diaprepes root weevil to low temperatures were used to generate a climate model in collaboration with APHIS to describe the current distribution of Diaprepes in Florida and to predict those regions in other U.S. states that are susceptible to establishment of Diaprepes. Work continued to determine the olfactory response of Diaprepes root weevil to plant and conspecific in collaboration with ARS scientists at the Chemicals Affecting Insects Behavior Lab. A patent was submitted on an attractant. Research on flight activity of Asian citrus psyllid revealed that psyllid routinely disperses to and from citrus trees at distances of up to 500 feet. There was evidence that a mass migration of adult psyllids may have occurred. If mass, long-distant migrations occur, this could have implications on psyllid management strategies. Yellow sticky card traps deployed in citrus trees were shown to have value in monitoring population trends of Asian citrus psyllid in citrus. However, numbers of adults captured on traps were inconsistent indicators of the absolute density of adults on mature leaves due in-part to positive influence of air temperature and sunlight on numbers of adults captured. Detailed information was obtained on reproductive biology and behavior of Asian citrus psyllid. Psyllid mates multiple times with multiple partners. Males and females find each other for mating using a combination of visual cues, sound, and a female-emitted sex pheromone. An auto-dissemination system was developed for introducing an entomopathogenic fungi into citrus for control of Asian citrus psyllid and other insect pests. Molecular genetic studies indicated that genetic diversity exists among chili thrips, which suggests that there may be a species complex of chili thrips. Differences could exist among chili thrips in susceptibility to insecticides and the ability to develop resistance to insecticides. Whitefly adults caused irregular ripening disorder to a tomato whether they infest leaves above or below a developing fruit. Production by whiteflies of the enzyme superoxide dismutase was directly proportional to increases in temperature in whiteflies feeding on disease-free tomatoes but inversely proportional in whiteflies feeding on virus-infected tomatoes. A survey of whiteflies in Guatemala revealed that the A, B and Q biotypes of the silverleaf whitefly were present. The Q biotype had not previously not been recorded in Guatemala.

1. Optimization of artificial diets for rearing exotic pests. While development or improvement of artificial insect diets can be tedious and convoluted, modest changes to insect diets can result in major economic benefits. Using n-dimensional mixture designs, we identified a set of response-optimized meridic diets that contain fewer ingredients than the current commercial diet for Diaprepes root weevil. A diet blend optimized to produce maximum adult weight was predicted to produce adult Diaprepes that weigh 28% more compared with adults reared on the standard commercial diet. Diet blends that produced greater individual adult weights resulted in lower survival compared with blends that yielded adults of more modest proportions. In contrast, a simplified high cottonseed meal blend produced smaller adults more similar to field-collected individuals, and produced the greatest number of adults and the greatest biomass at low cost compared with diets that yielded adult weevils of greater weight. Many insect-rearing programs would benefit from application of geometric experimental design methods to situations where diet optimization is desired for researcher-selected criteria. National Program 304 Crop Protection and Quarantine, Component II Biology of Pests and Natural Enemies (Microbes), Problem Area II (B) Rearing of Insects and Mites.

2. Develop a transgenic citrus rootstock with resistance to the Diaprepes root weevil. Transgenic alfalfa plants expressing the Bt-toxin gene were successfully shown as a model plant system to have a high level of Diaprepes root weevil resistance as compared to untransformed controls. Antibodies against the BT-toxin were developed and used to verify BT-toxin production in the transgenic alfalfa plants. Accordingly, transformation of a citrus rootstock was initiated. National Program 304 Crop Protection and Quarantine, Component V Pest Control Strategies, Problem Area B Breeding for Host Plant Resistance.

3. Asian citrus psyllid reproductive biology and behavior. Substantial data gaps existed in knowledge of the reproductive biology and behavior of Asian citrus psyllid. We determined time periods between the emergence of new adults, mating activities and egg-laying activities. We showed that the insect mates multiple times with multiple partners. We found that males and females find each other for mating using a combination of visual cues, sound, and a female-emitted sex pheromone. Mating occurred only during daylight hours. Abdominal coloration was not an indicator of reproductive maturity. National Program 304 Crop Protection and Quarantine, Component II Biology of Pests and Natural Enemies (Microbes), Problem Area A Basic Biology.

4. Sampling Asian citrus psyllid. Yellow sticky card traps deployed in citrus trees were shown to have value in monitoring population trends of Asian citrus psyllid in citrus. However, numbers of adults captured on traps were inconsistent indicators of the absolute density of adults on mature leaves. This was in-part due to the positive influence of air temperature and sunlight on numbers of adults captured. National Program 304 Crop Protection and Quarantine, Component VI Integrated Pest Management Systems and Areawide Suppression, Problem Area A Sampling Methods, Detection and Monitoring.

5.Significant Activities that Support Special Target Populations

6.Technology Transfer

Number of the New MTAs (providing only)1
Number of Invention Disclosures Submitted1

Review Publications
Boykin, L.M., Bagnall, R.A., Frohlich, D.R., Hall, D.G., Hunter, W.B., Katsar, C.S., McKenzie, C.L., Rosell, R.C., Shatters, R.G. 2007. Twelve polymorphic microsatellite loci from the Asian Citrus Psyllid, Diaphorina citri Kuwayama, the vector for citrus greening disease Huanglongbing. Molecular Ecology Notes.7:1202-1204. Available: Doi: 10.111/j1471-8286.2007.01831

Hall, D.G., Roda, A., Lapointe, S.L., Hibbard, K. 2008. Phenology of Maconellicoccus hirsutus (Green) Hemiptera: Pseudococcidae) in Florida based on attraction of adult males to pheromone traps. Florida Entomologist 91:305-310.

Hall, D.G., Hunter, W.B. 2008. Populations of sharpshooters in two citrus groves in east-central Florida as indicated by yellow sticky card traps. Florida Entomologist. 91(3):488-490.

Lapointe, S.L., Leal, W.S. 2007. Describing seasonal phenology of the leafminer Phyllocnistis citrella (Lepidoptera: Gracillariidae) with pheromone lure: controlling for lure degradation. Florida Entomologist. 90:710-714.

Sirot, L.K., Brockmann, H.J., Lapointe, S.L. 2007. Male post-copulatory reproductive success in the beetle, Diaprepes abbreviatus. Journal of Animal Behavior 74:143-152.

Wenninger, E., Hall, D.G. 2008. Daily and seasonal dynamics in abdomen color in Diaphoria citri (Hemiptera: Psyllidae). Annals of the Entomological Society of America. 101:585-595.

Wenninger, E., Hall, D.G. 2007. Daily timing of mating and age at reproductive maturity in Diaphorina citri (Hemiptera: Psyllidae). Florida Entomologist. 90:715-722.

Lapointe, S.L., Evens, T.J., Niedz, R.P. 2008. Insect diets as mixtures: optimization for a polyphagous weevil. Journal of Insect Physiology 54: 1157-1167.

Sirot, L.K., Lapointe, S.L. 2008. Patterns and consequences of mating behavior of the root weevil Diaprepes abbreviatus (Coleoptera: Curculionidae). Florida Entomologist. 91:400-406.

Setamou, M., Flores, D., French, J., Hall, D.G. 2008. Dispersion patterns and sampling plans for Diaphorina citri (Hemiptera: Psyllidae) in citrus. Journal of Economic Entomology. 101:1478-1487.

Hall, D.G., Hentz, M.G., Adair, R.C. 2008. Population ecology and phenology of Diaphorina citri (Hemiptera: Psyllidae) in two Florida citrus groves. Environmental Entomology. 37:914-924.

Last Modified: 9/23/2014
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