Location: Vegetable Crops Research Unit
Project Number: 3655-21220-002-10
Start Date: Aug 23, 2011
End Date: Sep 30, 2014
Objective 1. 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. Objective 2. Assessing metabolic resistance levels. CPB adults were collected from three VA locations in 2011 and assayed for baseline levels of three metabolic enzymes (esterase, glutathion-S-transferase, and cytochrome P450 monooxygenase) associated with detoxification mechanisms. A total protein content assay was also conducted on the three VA populations as well. The results from these baseline assays will be compared to enzyme assays conducted after exposing CPB adults from the same fields in 2012 to sub-lethal doses of different insecticides. These trials should indicate which detoxifying mechanisms are activated in CPB. The results of these experiments may provide insight into the potential resistance development of CPB. Objective 3. 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.