Field Studies with Systemic Insecticides against Cattle Grubs and Lice1

Abstract

In tests involving 270 calves treated orally with single doses of systemic insecticides in bolus form, Dow ET-57 (Trolene) and Dowco-109 (phosphoramidothioic acid, methyl 1-, O-(-4-tert- butyl-2-chlorophenyl) O-methyl ester), gave high kills of Hypoderma lineatum (DeVill.) and H. bovis (L.). Control with both insecticides exceeded 90%. Dow ET-57 appeared to be as effective at a dosage rate of 85 mg./kg. as at 110 mg./kg. Dimethoate (O,O,-dimethyl-S- (N-methylcarbamolymethyl) phosphorodithioate), also called Am. Cyanamid 12,880, gave only erratic control at rates of 15 and 10 mg./kg. None of the three insecticides, when given orally, killed 100% of cattle lice, but dimethoate produced higher kills than Dow ET-57 or Dowco-109. When given as feed additives to 160 calves, Dowco-109 at 2.0, 7.5, and 15 mg./kg. fed for 10,2, and 1 day, respectively, and Dow ET-57 at 55 mg./kg. fed for 2 days, caused grub reductions of 61 to 82%. Better results might have been obtained under more normal feeding conditions than prevailed in this test. As a complete coverage spray, Bayer 21/199 (Co-ral) 0.25 and 0.5% (from wettable powder) provided excellent louse control for at least 5 months. Dowco-109 (wettable powder) provided good louse control for a period of from 3 to more than 4 months. Neither Bayer 21/199 nor Dowco-109 gave satisfactory control of grubs under the conditions of these spray tests, although each gave about 80% control in one test at a concentration of 0.5%. It was concluded that Bayer 21/199 might potentially provide “one-shot” grub and lie control on cattle.