Efficacies of Chlorfenvinphos, Amitraz and Alphacypermethrin Acaricide Combinations on Rhipicephalus (Boophilus) decoloratus Adult Ticks and Larvae, from Cattle in Nandi County, Kenya

The acaricides chlorfenvinphos, amitraz and alphacypermethrin are commonly used to control cattle ticks in Nandi County, Kenya. Their efficacies are reportedly low, and farmers occasionally combine different classes in effort to improve it. However, their use at irregular concentrations has been documented. Engorged adult Rhipicephalus (Boophilus) decoloratus ticks were recovered from cattle dipped with either of the acaricides three days earlier, and their incubation yielded large batches of eggs that hatched to active larvae. Adult Immersion Tests in combinations of equal volumes of any two of the three acaricides, at recommended concentrations, produced 0 - 100 % efficacies after 96 hours. In contrast, Modified Larval Packet Tests had 95 - 100 % (Prob greater than F = 0.000) efficacies on their larvae in 24 hours. Combinations with chlorfenvinphos had high efficacies on adult ticks from cattle dipped in either alphacypermethrin or amitraz (Prob greater than F = 0.0000). Amitraz-alphacypermethrin combinations had low efficacies on all adult samples. The study showed that combinations of chlorfenvinphos with either amitraz of alphacypermethrin improved efficacies on the adults, while all combinations were effective on the larval stages.