ABSTRACT
Cyhalothrin, a novel synthetic pyrethroid, was evaluated for control of the major resistant strains of the cattle tick (Boophilus microplus) and for control of the buffalo fly (Haematobia irritans exigua) on cattle. In regulated treatment trials with 0.007% cyhalothrin, greater than 99% control of the Biarra, Mackay, Mt Alford, DDT resistant and Ulam cattle tick strains was obtained. Protective-period trials were conducted in which animals which had been sprayed with 0.007% cyhalothrin then received a continuing heavy challenge of the organophosphate-resistant Biarra tick strain. The first semi-engorged adult ticks appeared no earlier than 27 days after treatment, which corresponds to a minimum protective period against reinfestation of 7 days. Protective-periods ranging from 7 to 15 days were obtained in trials that were conducted. Field trials on cattle confirmed that dipping in 0.007% cyhalothrin provided a high level of tick control and a minimum of 7 days protective period against reinfestation. Thus a 28 day treatment interval was employed. It was possible to further extend dipping intervals to as long as 7 weeks once tick populations were reduced on the pasture. Furthermore at least 28 days protection from reinfestation with buffalo fly was also provided. In backspraying trials on cattle, 200 mg cyhalothrin applied to each animal as an 0.2% aqueous emulsion gave greater than 28 days protection against reinfestation with buffalo fly.
