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<OL> <LI> Determine if soybean aphid biotypes exists using an array of lines with known aphid resistance genes. <LI> Develop economic thresholds for soybean aphid that account for effects of natural enemies, plant growth stage, resistant cultivars, and key environmental pertubations.<LI> Discover if fungicides commonly used for soybean rust control adversely impact entomopathogenic fungi that regulate soybean aphid populations. <LI> Evaluate candidate insecticides for activity against key pests in potato (Colorado potato beetle and green peach aphid) and soybean (soybean aphid) and toxicity of these novel compounds to natural enemies of these key pests.
NON-TECHNICAL SUMMARY: Soybean aphid is a recently introduced insect from Asia that has forever changed how soybean is produced in North America. Prior to soybean aphid introduction in 2000, soybean was a crop that was rarely treated with insecticide, effectively making this crop a key untreated ecosystem in the landscape. This has now changed and it is not uncommon to have more than 50% of the soybean crop treated with one or more insecticide applications to control soybean aphid and to prevent devastating losses. Aphids in general and specifically soybean aphid are vectors of plant viruses. Virus can reduce yield, affect quality of the harvested fruit or tubers, and there is little that can be done to prevent viral epidemics. We have specifically focused on transmission of Potato Virus Y, a viral pathogen of potato and other crops that is readily transmitted by soybean aphid. One non-chemical approach to soybean aphid control is to allow natural enemies to control aphid outbreaks. We are focusing our efforts on understanding what situations favors control by natural enemies and what situations will natural enemies be overwhelmed. The best way to preserve natural enemies is to provide producers with reliable data on yield loss attributed to aphids and provide answers to questions like: "How many aphids are too many aphids?", "Can predators, parasites and pathogens of aphids reliably control an aphid outbreak?", "Are there safer alternatives when choosing an insecticide to use to control soybean aphid?", "Will there be resistant soybean varieties that I can use available in the future?", and "If I plant a resistant soybean variety will aphids that can use this resistant variety develop?"
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APPROACH: 1. Small plot and cage studies conducted at various Agricultural Research station using an array of PIs and cultivars with known aphid resistance genes will be used in a regional approache to determine if aphid biotypes exist and can overcome plants with identified aphid resistance genes, e.g., RagI, RagII and others. <P>2 Replicated field trials to refine published economic threshold for soybean aphid using observations on natural enemy density, quantifying rainfall events (amount and duration), and plant variety and growth stage on aphid population growth. <P>3. Field and laboratory studies to measure effects of various fungicides used against soybean rust and other soybean pathogenhs have on entomopathogenic fungal species and their effects on aphid population growth.<P> 4. Laboratory studies will be used to measure toxicity of various candidate insecticides on a variety of aphid species and other insect pests and their natural enemies. Tests will conform to the UN FAO guidelines on toxicity testing.