Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 27, 2000
Publication Date: N/A
Interpretive Summary: The horn fly, Haematobia irritans (L.), is an economically important pest of cattle. Introduction of various classes of chemicals for the control of this pest has resulted in the eventual development of resistance to the control chemical. Insecticide resistance is a major problem for producers and the chemical industry. Insects possess adaptive physiological, behavioral, and biochemical mechanisms that allows the population to cope with the stress of insecticide application. Metabolic enzymes are capable of detoxifying insecticides. In this study we described a single fly micro-assay that measures the fly's ability to detoxify permethrin with a class of metabolic enzymes called esterases. In addition, we evaluated the variation in general and permethrin esterase activity within our insecticide susceptible horn fly colony. Our goal is to elucidate metabolic mechanisms of insecticide resistance, and with that knowledge design diagnostic assays that will allow us to know more about population genetics, detect the development of resistance earlier, and track changes in the population as a result of efforts to mitigate resistance.
In this study we describe a nonradioactive single fly micro-assay for permethrin hydrolysis. We use this assay with a microplate assay for general esterase activity to evaluate the permethrin hydrolyzing and general esterase activities of aging pyrethroid susceptible male and female horn flies, Haematobia irritans (L.). We found substantial gender and age related differences regarding general esterase activity, permethrin sensitivity, and permethrin hydrolyzing activity within the colony. Extracts of female flies collected 48 h after receiving their first blood meal yielded significantly greater esterase activity than male extracts. Aging female flies were more tolerant of permethrin than were male flies. In addition, a positive correlation was found to exist between the general esterase activity of aging females and their ability to hydrolyze permethrin.