a1 ODA Insect Pest Management Initiative, Tsetse & Trypanosomiasis Control Branch, Harare, Zimbabwe
a2 Regional Tsetse & Trypanosomiasis Control Programme, Harare, Zimbabwe
Deposits of deltamethrin suspension concentrate (s.c.) on Terylene net and cotton cloth were bioassayed in Zimbabwe by exposing them to fed, female Glossina pallidipes Austen, using a 45 s contact with cloth and a brief collision with net. On textured yarn net, the effective life of deposits produced from immersion in 0.1% deltamethrin was longer than on flat yarn net, apparently because the textured net held more insecticide and the insecticide was lost more slowly. The addition of an absorber for ultra-violet light (0.1% 2-hydroxy-4-methoxybenzophenone-5-sulphonic acid) did not significantly extend the effective life of deltamethrin deposits on cloth or net. Applying deltamethrin s.c. as a 0.6% suspension to cotton cloth produced mortalities of <90% for 300 days. Applications of 0.8% deltamethrin on cotton cloth and textured net produced mortalities of <70% for 12–16 months and 9 months, respectively, compared to 4–10 months and 5–7 months, respectively for applications of 0.1% deltamethrin. Chemical analyses indicated that the longer effective life of the 0.6–0.8% was due to a higher initial amount of insecticide and a lower rate of loss. It is suggested that for controlling tsetse in southern Africa, all-cloth targets sprayed with 0.6% deltamethrin s.c. will have an effective life of ca. one year.
(Accepted May 19 1992)
c1 Dr. S. Torr, Tsetse Control Branch, PO Box 8283, Causeway, Harare, Zimbabwe.