Cattle ticks, Boophilus microplus, resistant to DDT, BHC, and Dieldrin

Abstract

Cattle ticks on a property in central Queensland, where there had been a previous history of DDT-resistance, were not readily controlled by dipping infested cattle in 0.05 per cent. w/v gamma-BHC or 0.05 per cent. w/v dieldrin after these chemicals had been in use for 10 and 4 months respectively. Spraying of steers artificially infested with ticks taken from this property 9 months later, indicated resistance to DDT and dieldrin, but not to "Diazinon". Immersion tests with larvae and engorged adult females of this strain showed them to be respectively about 9 and 20 times as resistant to DDT as those of a susceptible reference strain. The engorged females were shown to be more than 700 times as resistant to dieldrin. When tested by an injection method, the engorged adult females of this strain showed a resistance to DDT and dieldrin of 5 and 12 times respectively, some resistance to BHC, but no resistance to Bayer 21/199. Similarly tested engorged adult females of another strain taken from the property 15 months later showed a resistance to DDT of 8 times.