Microencapsulated permethrin for controlling Boophilus microplus on cattle in south Texas

A study was conducted at the USDA-ARS, Cattle Fever Tick Research Laboratory, Mission, Texas, to determine the efficacy of a 0.05 and 0.1% microencapsulated 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 on the King Ranch in Kleberg County, Texas, to determine the stability of 0.05% microencapsulated permethrin formulation in a dip vat under South Texas conditions. Cattle were infested with all parasitic life stages of B. microplus and were sprayed or dipped with a concentration of 0.05 and 0.1% microencapsulated permethrin. As determined by the index of reproduction, the 0.05 and 0.1% whole-body spray treatments provided 85.8 and 96.2% control, respectively, and the 0.05 and 0.1% dip vat treatment provided 98.2 and 99.3% control, respectively. Laboratory bioassay results compared favorably with those obtained with the spray and dip vat treatment. The microencapsulated permethrin remained stable in the ranch vat for three to four weeks. After four weeks, the vat solution began turning black and became foul, apparently due to bacterial growth. In addition, the microencapsulated permethrin became very difficult to resuspend.