Substitutes for Rotenone in Cattle Louse Control

ests were made in 1941-43 of the effectiveness of certain dusts in the control of Damalinia (Bovicola) bovis L., Linognathus vituli L., Solenopotes capillatus End., and Haematopinus eurysternus Nitzsch, on cattle in New York, where, as in other parts of the north-eastern United States, lice are serious pests of dairy herds in winter and early spring. A mixture of 1 part cubé (5 per cent, rotenone) and 10 parts wettable sulphur was found to give excellent control of all species in 1941-42. In the following winter, various substitutes were tested as rotenone-bearing dusts are difficult to obtain. The usual dose was 3-4 oz. per animal, applied with a puff duster having a wide nozzle and canvas flaps to help confine the dust. The best results were obtained with a dust of 1 part finely ground sabadilla seed to 10 parts wettable sulphur, which gave complete kill of three species and 95 per cent, kill of S.capillatus in 7 days. Ground seed of the yam bean, Pachyrhizus erosus [cf. R.A.E., A 31 502] at the same strength was almost as effective. In neither case was there appreciable reinfestation within 3 weeks. Even at 1: 20, sabadilla gave practically perfect control of all lice except S. capillatus. Thanite (secondary terpene alcohol thiocyanate) and lethane (beta-thiocyanoethyl esters of fatty acids), each at 1 part to 2 parts Celite and 8 parts sulphur gave 60-95 per cent. kill. S. capillatus was particularly resistant to them. Dusts that were ineffective at 1 part to 10 parts sulphur comprised proprietary free or fixed nicotines (Black Leaf 10 or 155) [but cf. B 32 100], pyrethrum (Stimtox A) and hellebore. Velsicol (isomeric mixture of alkyl substituted naphthalenes) at 1 part to 2.5 parts Celite and 7.5 parts sulphur gave poor kills in 7 days, but good control over a longer period. Laboratory tests in which 10-15 females of D. bovis were placed on uniform deposits of the dusts confirmed the results of the field trials. Sabadilla was second in toxicity to rotenone, and nicotine only slightly better than sulphur. The only discrepancy in the results was in the case of yam-bean seed, which was only slightly toxic in the laboratory tests. This may be because its action is slow.