Permethrin as a residual insecticide against cockroaches

Abstract The pyrethroid permethrin was shown to be active against Blattella germanica, Periplaneta americana and Blatta orientalis. In laboratory tests on plywood panels the best formulation was a 25% wettable powder which showed an initial LC50 of 10 mg m−2 against B. germanica and lost activity at the weekly rate of 1.9 mg m−2. An initial deposit of 108 mg m−2 gave 50% kill after one year. The synergist piperonyl butoxide diminished residual performance. In one field trial, good control was maintained for more than four months with an initial deposit of 50 mg m−2, the smallest dose used. From this and other trials, the recommended rate of application for general use in long‐term control is 100 mg m−2. A distinctive slow expellent action against B. germanica was seen in field trials.