EFFICACY OF ZETA-CYPERMETHRIN AS POUR-ON OR SPRAY FORMULATIONS FOR THE CONTROL OF BUFFALO FLY (HAEMATOBIA-IRRITANS EXIGUA) IN CATTLE

Objective To determine the efficacy of zeta-cypermethrin in controllin g buffalo fly (Haematobia irritans exigua). Design Five field trials i n northern and central Queensland. Procedure Zeta-cypermethrin pour-on at 2.5 mg/kg, spray at 62.5 ppm, deltamethrin pour-on and pour-on veh icle were applied to groups of 20 cattle. Buffalo fly counts were cond ucted three times before treatment and 3, 7, 14, 21, 28 and 35 days af ter treatment. Results In central Queensland where synthetic pyrethroi d resistance in buffalo fly populations was rare, 2.5 mg/kg of zeta-cy permethrin pour-on gave good control of buffalo fly for 4 weeks and wa s better than a deltamethrin product. A zeta-cypermethrin spray used a t 62.5 ppm gave 14 days control. In far-north Queensland where resista nce to synthetic pyrethroids and heavy rain was common, the maximum pe riod of efficacy of zeta-cypermethrin pour-on was reduced to 2 weeks. Conclusion In areas where there is low resistance to synthetic pyrethr oids among buffalo flies, zeta-cypermethrin pour-on can be expected to give good control for 4 weeks.