MICROENCAPSULATED PERMETHRIN SPRAYS FOR CONTROL OF SOUTHERN CATTLE TICK, BOOPHILUS-MICROPLUS (CANESTRINI) (ACARI, IXODIDAE), INFESTING HOLSTEIN DAIRY HEIFERS ON SAINT-CROIX, US VIRGIN-ISLANDS

The effectiveness of two acaricides was evaluated for control of popul ations of the southern cattle tick, Boophilus microplus on dairy cattl e in St. Croix, U.S. Virgin Islands. Two different concentrations of a microencapsulated (ME) formulation of permethrin (0.05% and 0.10% al) and one concentration of coumaphos emulsifiable concentrate (EC) (0.1 17% al) were sprayed on Holstein heifers that had a natural infestatio n of ticks. The length of residual activity of EC coumaphos and ME per methrin at 0.05% (al) was at least four days, and for ME permethrin at 0.10% al at least seven days. There was no apparent increase in the r esidual activity period of ME permethrin in comparison to that in fiel d trials of other formulations of permethrin against B. microplus. Per centage control for the three treatment groups from days 4 through 21 was ME permethrin (0.05% al) 96%; ME permethrin (0.10% al), 97%; couma phos, 98.3%. There were no significant differences among the treatment groups (F = 2.21, df = 2, 17, P > 0.10). This research confirms the u sefulness of permethrin as an alternative to coumaphos for control of B. microplus populations on cattle.