Control of Three-Host Ticks: Laboratory Tests of Systemic Insecticides in Feed of Cattle13

Abstract

When the feeding of 6 systemic insecticides to individually stanchioned cattle was started 2-26 days before the cattle were infested with adults and nymphs of Amblyomma americanun (l..), the lone star tick; A. maculatum Koch, the Gulf Coast ticks; and Dermacentor variabilis (Say), the American dog tick; and continued throughout the engorgement period, famphur at 5 mg kg per day was the most effective treatment. With adults, this treatment was highly active against Gulf Coast ticks (100% control of Estimated Larvae (EL); EL = g eggs × estimated % hatch × 20,000) and lone star ticks (>99.5% control of EL), but less active against American dog ticks (19.83% control of EL). Also, famphur at 2.5 mg /kg per day was effective against Gulf Coast ticks but only partially effective against the other 2 species. Fenthion at 1.25 mg/kg per day was effective only against Gulf Coast ticks. The other treatments, 1.5 mg/kg per day of coumaphos, 3 mg/kg per day of cruformate, 1.5 mg/kg per day of Imidan ( O, O -dimethyl phosphorodithioate S -ester with N -(mercaptomethyl)-phthalimide), and 7 mg/kg per day of runnel, were ineffective (afforded 0-14% control of EL). With nymphs, famphur at 5 mg/kg per day prevented engorging of nymphs of the Gulf Coast tick, was slightly less effective against nymphs of the lone star tick, and only partially effective against nymphs of the American dog tick. The other treatments failed to prevent engorging of nymphs. With almost all treatments, nymphs that engorged molted to adults.