Submitted to: Journal of Economic Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: December 16, 1998
Publication Date: N/A
Interpretive Summary: Horn flies are a blood-feeding parasite of cattle which has begun to develop resistance to some insecticides in many regions of the United States. Organophosphate (OP) insecticides are becoming increasingly relied upon to control horn flies as resistance to this insecticide class is not yet widespread. One biochemical mechanism by which insects may develop resistance to OPs is through the production of esterase proteins which can sequester and/or detoxify the insecticide. Populations of horn flies exhibiting varying degrees of OP-susceptibility or -resistance were tested by esterase dot blot assays. Individuals from an OP-resistant population was found to display high overall esterase activity and produce an OP- insensitive specific esterase called acetylcholinesterase. Polyacrylamide gels analysis revealed a complex qualitative and quantitative profile of esterases which varied considerably among individual flies, with 28 different esterase bands identified. The results indicate that a number o specific esterases may contribute to diazinon resistance in the horn fly.
A field population of horn flies, Haematobia irritans irritans (L.), exhibiting diazinon resistance in bioassays also displayed high overall esterase activity and OP-insensitive acetylcholinesterase in dot blot activity assays. Native polyacrylamide gels yielded a complex qualitative and quantitative profile of esterases which varied considerably among individual flies from 9 populations, with 28 different esterase bands identified. The results from topical diazinon application experiments and subsequent analysis indicate that a number of specific esterases may contribute to diazinon resistance in the horn fly.