Effect of the various substrates on the insecticidal activity of fenitrothion and permethrin against the German cockroach, Blattella germanica (L.)

Abstract

Contact effectiveness of insecticide often fluctuates due to the characteristics of the substrate treated with insecticidal formulations. The effect on the toxicity of two insecticides, fenitrothion and permethrin, applied on the different substrates were evaluated against female adults of the German cockroach, Blattella germanica (L.) by continuous contact method. Six substrates including plywood, cotton cloth (adhered on plywood), and blicks as the porous materials and stainless steel, tiles, and varnished plywood as the non-porous ones were chosen for this purpose. As a whole, both insecticides treated on the non-porous substrates showed the higher effectiveness than those treated on the porous ones. However, the effectiveness of fenitrothion seemed to vary greatly among the substrates when compared with permethrin. In the tests with permethrin, the residual effectiveness increased with the day's lapse, presumably due to a blooming effect of the insecticide. Repeated use of insecticidal residues reduced the effectiveness more in the non-porous substrates than those in the porous ones. Decreasing volume of the spray from 50ml to 25ml per square meter did not affect the effectiveness on the non-porous materials.