Characterization of the Organophosphoms-resistant Mt Alford, Gracemere and Silkwood Strains of the Cattle Tick, Boophilus microplus

Abstract

Dosage-mortality tests on larval ticks have indicated that the Mt Alford and Gracemere strains of B. micro pius differ from the Biarra and Ridgelands strains respectively, not only as previously reported by exhibiting markedly greater resistance to both chlorpyrifos and diazinon, but also by exhibiting moderately greater resistance in the Mt Alford strain to bromophos-ethyl and dioxathion and in the Gracemere strain to carbophenothion and coumaphos. Their responses to other chemicals were similar to those of the Biarra and Ridgelands strains respectively.