Dieldrin-resistant cattle ticks, Boophilus microplus (Canestrini) in Queensland

Abstract

Infestation by cattle ticks in a herd a t Mt. Gravatt, near Brisbane, in southern Queensland, could not be controlled by repeated spraying of the cattle with 0.05 per cent. w/v dieldrin. Ninety-eight per cent. of engorged females of this strain, which fell from an artificially infested beast in the 48 hr following spraying with 0.05 per cent. w/v dieldrin, laid normal batches of viable eggs. Spraying cattle with 0.05 per cent. w/v "Diazinon", however, readily controlled infestation by this strain. Laboratory concentration-response tests on a culture of the dieldrin-resistant ticks indicated that the median lethal concentration of dieldrin for the larvae was over 2000 times higher than for those of a reference strain. There was also strong evidence from laboratory tests of dieldrin resistance in the engorged adult female ticks.