Compounds more toxic to fleas than DDT.

Abstract

Summary Laboratory tests were conducted with 620 insecticides to evaluate their effectiveness in dusts against the cat flea, Ctenocephalides felis (Bouche) and the oriental rat flea, Xenopsylla cheopis (Rothsch.). Recrystallized DDT was used as a standard of comparison. At a concentration of 0.5 per cent, 29 compounds were more effective than DDT, 24 were within the range of effectiveness of DDT, and 566 were less effective than DDT. The outstanding toxicants were heptachlor, dieldrin (compound 497), aldrin (compound 118), and benzene hexachloride (95 per cent gamma isomer). Chlordane and parathion were more effective than DDT at concentrations of 0.5 and 0.05 per cent, and toxaphene and pyrethrum extract plus piperonyl butoxide at 0.5 per cent only. Methoxychlor and other analogs were about equal to DDT. Thirty-three compounds were more toxic to cat fleas than to rat fleas, whereas only two, benzene hexachloride and pyrethrum extract plus piperonyl butoxide, were more toxic to rat fleas. Dusts of 13 of the better toxicants showed no evidence of deterioration after 10 to 12 months of storage, and with 3 others the evidence was not conclusive.