Toxicity of Various Carbamates and Synergists to Several Strains of Body Lice

Abstract

Sixty carbamates were screened as insecticides against a nonresistant strain of body lice. Six of the most effective and three from previous screening were tested more extensively. The most effective material, Hercules AC-5727 (m-isopropylphenyl methylcarbamate), killed 100% of adult lice at concentrations as low as 0.0025% in impregnated wool cloth, was 100% effective for more than 91 days at 1% in a pyrophyllite powder, and, at 0.5%, prevented any hatch of eggs. It was faster in knockdown action than malathion or lindane. Sevin® (1-naphthyl N-methylcarbamate) had a long residual effect and was highly synergistic with sulfoxide and piperonyl butoxide against adults and with sulfoxide against eggs. In sleeve tests against DDT-resistant lice, pyrophyllite powders containing 1% of Sevin plus 10% of sulfoxide and 2% of Sevin plus 2% of sulfoxide were 100% effective for more than 28 days. Powders containing 1% of Sevin plus 1% of sulfoxide or 2%, 3%, or 5% of Sevin alone were 98% to 100% effective for 10 days. A strain of DDT-resistant lice, which was more susceptible to Sevin than a strain of nonresistant lice, lost no resistance to DDT and acquired no resistance to Sevin when selected with Sevin for 30 generations.