Screening of Acaricides for Control of One-Hcst Ticks, 1980

Larvae of Boophilusannulatus (Say), the cattle tick, and B. microplus (Canestrini), the southern cattle tick, in colony at Falcon Heights, TX, and Anocentornitens (Neumann), the tropical horse tick, and Dermacentoralbipictus, (Packard), the winter tick, at Kerrville, TX, are placed onto cattle. Engorged females that detach naturally are used in the test. Usually candidate compounds (technical materials) are formulated as emulsifiable concentrates containing 25% active ingredient, 65% xylene, and 10% Triton X-100. Compounds not soluble In xylene are formulated in a 1:1 mixture of N-methyl-2-pyrrolidinone and the xylene-Triton X-100 combination. Commercial wettable powders or emulsifiable concentrates may be used. All formulations are mixed with water immediately before treatment. Acaricides are routinely tested at 1, 0.1, and 0.01% active ingredient; the lesser concentrations are obtained by serial dilution of the 1% concentration. For treatment, ticks are washed, dried, sorted into groups of 10, weighed, and placed into 45-50 ml of acaricide, which is stirred vigorously for 30 sec and then poured through a screen that retains the ticks. Drained ticks are placed on paper toweling to dry and then held in 8-dram shell vials at 27±1°C and>80% RH for oviposition. After 2-3 weeks, the ticks are discarded; however, the eggs are weighed and held for another month, at which time percentage hatch is estimated visually. Controls, groups of 10 ticks, are dipped in an emulsion of 2.6% xylene and 0.4% Triton X-100 or the mixture of xylene, Triton X-100 and methyl-pyrrolidinone and handled as treated ticks.