ADDITIONAL STUDIES WITH NEW INSECTICIDES AS RESIDUAL SPRAYS IN BUILDINGS NATURALLY INFESTED WITH ANOPHELES QUADRIMACULTATUS.

Because some species of Anopheles mosquitos have been developing resistance to DDT and dieldrin, field studies have been conducted to evaluate the effectiveness of recently developed insecticides as residual sprays in buildings naturally infested with adults of Anopheles quadrimaculatus. As a deposit at 2 g/m(2), o-isopropoxyphenyl methylcarbamate remained highly effective for more than one year. This compound and 6-chloro-3,4-xylyl methylcarbamate were still producing excellent control 11-12 weeks after application at 1 g/m(2). Other highly effective materials were m-isopropylphenyl methylcarbamate and 4-(methylthio)-3,5-xylyl methylcarbamate at 2 g/m(2). At the present time, o-isopropoxyphenyl methylcarbamate appears to offer the best prospects for use in residual spray programmes because it has long residual action, affects mosquitos rapidly, has only a slight odour and appears to be safe to use if spraymen take reasonable precautions.