Effect of low temperature treatment on the quality of male adult Glossina pallidipes (Diptera: Glossinidae) in relation to the sterile insect technique.

Abstract

Abstract
The effect of low temperatures on male pupae (pharate adults) and adults of Glossina pallidipes was assessed in relation to their use in sterile insect technique (SIT) programmes for the eradication of populations of this important disease vector in Africa. Since only male insects require to be released for the SIT, sex separation at some stage of development can be advantageous. For tsetse, sex separation exploiting the temporal difference in emergence pattern of females and males has enabled the direct stocking of fly production cages for G. austeni and G. pallidipes, leaving male pupae available for further handling. With some species of tsetse, e.g. G. pallidipes, it is important that males attain sexual maturity before they are released and therefore a planned and synchronized emergence of males would be beneficial. A protocol for controlled emergence based on low temperature treatment of mature male pupae is under development. Male pupae were incubated at 15°C, 18°C or 20°C for 24, 48 or 72 h and thereafter allowed to emerge at either 23-24°C or 26.5°C. In order to simulate the proposed use of the chilled adult release system for areawide tsetse SIT, adult males were stored at 7°C for 18, 24, 48 and 72 h followed by 6 h at 4°C. Emergence rate, survival without blood and insemination capacity were not significantly affected by low temperature storage of pupae. Chilling of adults resulted in lower insemination capacity and 10-32% mortality one day after removal from low temperature. Low temperature treatment of pupae delayed eclosion of G. pallidipes by 2-3 days. The potential uses of these procedures in an operational SIT programme are discussed.