The susceptibility of Glossina pallidipes Austen (Diptera: Glossinidae) to insecticide deposits on targets

Abstract

AbstractStudies were made of the susceptibility of wild-caught females of Glossina pallidipes Austen to deposits of DDT, dieldrin and deltamethrin on cotton canvas and Terylene netting. Aqueous suspensions of 3% dieldrin wettable powder, 3% dieldrin emulsifiable concentrate, 5·0% DDT wettable powder and 0·0625% deltamethrin flowable concentrate, were sprayed on the canvas at 0·36% litre/m2 Over 95% of the flies resting for 45 s on fresh deposits of these insecticides died within 72 h. Deposits of dieldrin, DDT and deltamethrin exposed to the sun during 140 days of the dry season produced mortalities of 100, 0 and 10% compared with 100, 75 and 100% for shaded deposits. The concentration of dieldrin and deltamethrin on exposed canvas was about 1% that on shaded canvas, but dieldrin produced photodieldrin upon exposure to the sun. Flies colliding with Terylene netting that had been immersed in 0·75–6·0% suspensions of dieldrin wettable powder and 0·01–0·1% suspensions of deltamethrin flowable concentrate produced mortalities of 100%. Deltamethrin deposits were resistant to weathering by rain, but dieldrin deposits were not. It is suggested that deltamethrin flowable concentrate should be used during the wet season and that dieldrin wettable powder should be used during the dry season. Dieldrin sprayed on an electrocuting target reduced the catch, but deltamethrin did not.