Small-scale field tests with dermally applied animal systemic insecticides for control of the common cattle grub.

Abstract

Small groups of cattle in Texas were treated dermally with systemic insecticides in the summer and checked in the fall to determine whether larvae of Hypoderma lineattun (de Villers) had been controlled. Cattle treated with trichlorfon (½ oz/cwt of an 8 or 16% pour-on or 1 gal/animal of 1% whole-body spray) had 95-100% fewer grubs than untreated cattle. Cattle treated with fenthion (½ oz/cwt of a 2% pour-on or 1 gal/animal of a 0.05 or 0.1% spray) had only 74-79% fewer grubs than the controls. Imidan® ( O,O -dimethyl S-phthalimidomethyl phosphorodithioate) as a pour-on gave better than 90% control at dosages of 13 mg/kg or more and less than 90% control at dosages of 7-13 mg/kg; generally, control was related to the amount of active ingredient per animal. Famphur administered as a pour-on (½ oz/cwt of 12.5%) gave 93% control; ½ that dosage gave 72% control. Coumaphos administered in May, June, July, or August gave 90-99% control as a 0.375% spray (1 gal/animal) and 80-95% control as a 4% pour-on (½ oz/cwt). Crufomate administered in the same months gave 90-99% control as an 8% pour-on (1 oz/cwt); a 0.5% spray (1 gal/animal) gave 50% control when administered in July but 81-89% control when applied in May, June, or August. Trichlorfon, also adminstered in the same months, gave 86-99% control as a 1% spray (1 gal/animal); an 8% pour-on (1 oz/cwt) gave 92-93% control after treatment in May, June, or July but only 68% control after administration in August. In general, lower control figures are the result of finding large numbers of grubs in 1 or 2 of the 4-5 cattle treated each month.