a1 International Centre of Insect Physiology and Ecology, Nairobi, Kenya
A field trial was carried out in a Maasai group ranch to assess the use of odour-baited traps for suppression of a population of the tsetse fly Glossina pallidipes Austen. In January, 1987, local people made 100 NG2B traps in their homesteads. These were then deployed within the suppression zone of about 100 km2, primarily in the areas of woodland where flies aggregate in the dry season. Traps were baited with acetone (ca. 150 mg/h) and cow urine (ca. 1000 mg/h) and checked at monthly intervals in order to replenish odours and repair damage. A further 90 traps were added between October and December to enlarge the suppression area slightly and to strengthen the trap barriers. The population was monitored using biconical and NG2B traps as well as by mark-release-recapture estimates of population size. By October the number of G. pallidipes in the suppression zone was reduced by 98–99% relative to the number 3 km outside the suppression zone. Some reinvasion, mainly of parous females, occurred in November during the short rains but these flies were rapidly trapped out again. Average mortality rates due to trapping were estimated at 4–5% per day, which, combined with the natural mortality, reduced the adult population at a rate of about 2.6% per day during the dry season. The traps had less effect on the smaller population of G. longipennis Corti but still gave a reduction of up to 90% in the dry season. The use of this low technology approach offers good prospects for future community-based tsetse control operations.