Effect of physiological age and pregnancy stage on the tolerance of Glossina species to aerosol and topical application of endosulfan and the consequences for aerial control

Abstract

Thiodan, a ULV formulation of endosulfan, was applied as an aerosol to field‐caught Glossina pallidipes and G. morsitans morsitans held in a wind tunnel. Mortality was noted during a 48 h post‐spray period and all female flies were dissected to assess their physiological age and stage of pregnancy. A second experiment using topical application of technical endosulfan to laboratory‐bred flies was used to supplement data on G. m. morsitans. Male flies were found to be more susceptible than female flies. Physiological age was found to have little effect on tolerance to the insecticide, but the presence of a second‐ or third‐stage larva in the uterus significantly increased tolerance compared with other pregnancy stages. Flies larvipositing during the topical application experiment were more tolerant than any other group of G. m. morsitans. It is common practice, whilst controlling tsetse using the sequential aerosol technique, to reduce application rates after the first cycle. This study indicates that application rates should be maintained or spraying should commence before newly emerged flies enter the later stages of pregnancy.

Keywords:

• Tsetse
• Endosulfan
• Glossina pallidipes
• Glossina morsitans morsitans
• Sequential aerosol technique