THE RESIDUAL ACTION OF TWO ORGANOPHOSPHORUS COMPOUNDS AND A CARBAMATE ON DRIED MUDS.

Laboratory experiments have shown that the sorption of two organophosphorus compounds, malathion and fenthion, and a carbamate, UC 10854, on dried muds is influenced by atmospheric humidity and that the biological activity of a given concentration of sorbed insecticide increases with increasing humidity. The residual action of these insecticides on dried mud bricks stored in the laboratory at 25 degrees C and 80% relative humidity was similar to that obtained in experimental huts at Arusha, Tanganyika.The laboratory bio-assays indicate that both fenthion and UC 10854 can be expected to have several weeks' residual action on dried mud walls provided that the atmospheric humidity is high enough. Malathion was much less effective in the test conditions described in this paper, but field data suggest that it has a long residual action on grass roofs.