MICROENCAPSULATED PERMETHRIN FOR CONTROLLING BOOPHILUS-MICROPLUS ON CATTLE IN SOUTH TEXAS

A study was conducted at the USDA-ARS, Cattle Fever Tick Research Labo ratory, Mission, Texas, to determine the efficacy of a 0.05 and 0.1% m icroencapsulated permethrin formulation applied as a whole-body spray, in a standard dip vat, and in a laboratory bioassay against Boophilus microplus (Canestrini) on cattle. An additional study was conducted o n the King Ranch in Kleberg County, Texas, to determine the stability of 0.05% microencapsulated permethrin formulation in a dip vat under S outh Texas conditions. Cattle were infested with all parasitic life st ages of B. microplus and were sprayed or dipped with a concentration o f 0.05 and 0.1% microencapsulated permethrin. As determined by the ind ex of reproduction, the 0.05 and 0.1% whole-body spray treatments prov ided 85.8 and 96.2% control, respectively, and the 0.05 and 0.1% dip v at treatment provided 98.2 and 99.3% control, respectively. Laboratory bioassay results compared favorably with those obtained with the spra y and dip vat treatment. The microencapsulated permethrin remained sta ble in the ranch vat for three to four weeks. After four weeks, the va t solution began turning black and became foul, apparently due to bact erial growth. In addition, the microencapsulated permethrin became ver y difficult to resuspend.