Esterase profiles of diazinon-susceptible and -resistant horn flies (Diptera: Muscidae)

Abstract

A field population of horn flies, Hematobia irritans irritans (L.), exhibiting diazinon resistance in bioassays also displayed high overall esterase activity and organophosphate-insensitive acetylcholinesterase in dot blot activity assays. Native polyacrylamide gels yielded a complex qualitative and quantitative profile of esterases that 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.