Location: Vegetable Crops Research Unit
Project Number: 3655-21220-002-09
Start Date: Sep 12, 2011
End Date: Sep 30, 2014
Resistance monitoring. Cooperators representing the US potato industry from different states will receive collection kits including shipping containers and USDA-APHIS permits. Each Colorado potato beetle (CPB) population will be screened to determine the relative susceptibility to imidacloprid and thiamethoxam (topical application, 15 adults per concentration, five concentrations, 150 beetles per insecticide). Treated beetles will be placed in Petri dishes lined with filter paper and fed fresh potato foliage and kept at 24°C (±1). Beetle mortality will be assessed 7 days after treatment. Doses lethal to 50% of the beetles (LD50s) for imidacloprid and thiamethoxam will be determined by log dose/probit mortality analysis. LD50s for field populations will be compared to LD50s for susceptible beetles to determine whether resistance to either chemical is increasing in the field. Resistant populations will be mapped to see if resistance appears to be spreading or occurring in new locations. Efficacy of alternative insecticides. Preliminary research with the novel insecticide tolfenpyrad has shown a high level of toxicity to CPB larvae and adults in the lab and field. In 2012, we will conduct bioassays to measure LC50 levels and to determine optimal rates of this chemical to use in the field. In addition, we will evaluate the efficacy of several other novel insecticides including cyantraniliprole, spinetoram, and others. Plant resistance. We will identify and compare chemicals emitted into the headspace of wild relatives of the cultivated potato that show various levels of resistance to CPB. Volatiles that are specific to and are abundantly produced by CPB resistant Solanum species will be evaluated for CPB behavior modifying activity. Wild species clones selected for the production of behavior modifying volatiles will be crossed to the cultivated potato. The hybrid offspring will be selected for adaptation, fertility and resistance to CPB. Resistance bioassays will be carried out in the laboratory and the field. We will identify volatiles from resistant plants and use this to inform potato breeders about an unattractive or repellent potato volatile profile, which can be combined with traits that reduce CPB development, increase CPB mortality and slow the development of insecticide resistance. Our ultimate goal is to combine multiple resistance mechanisms into a clone that delays CPB resistance development and provides long lasting broad-spectrum crop protection.