| Abstract: | Ovicidal activity of coumaphos, diazinon, dioxathion, chlorpyrifos, and crotoxyphos applied topically at 0.125, 0.25, and 0.5% (AI) to 1-d-old, 10-d-old, and 20-d-old eggs of southern cattle tick, Boophilus microplus (Canestrini), was determined. All acaricides produced some disruption of hatching of eggs in all age classes. Coumaphos, diazinon, dioxathion, and chlorpyrifos were most effective in reducing egg hatch of 1-d-old eggs but had little effect against 10- or 20-d-old eggs. Although crotoxyphos was comparable with other acaricides in reducing hatch in 1-d-old eggs, it caused significantly greater mortality (greater than or equal to 94.6%) in 20-d-old eggs than other compounds tested. Crotoxyphos applied at 0.5% (AI) is the only acaricide tested that provided sufficient ovicidal activity in all three egg age classes (greater than or equal to 85% reduction of hatch). |
