Experiments were carried out to improve the NG2B tsetse trap (Brightwell et al., 1987), baited with acetone and cow urine, for use by rural communities to control G.pallidipes Austen and G.longipennis Corti. Modifications included a lower dose rate of acetone, a new cage design and raising the trap about 15-20 cm. Research on different trap cone materials showed that the degree of light transmission of the netting, rather than its colour, was the crucial factor affecting the catch of G.pallidipes. Adding an additional metre of blue cloth to one side of the trap increased catches of females of both species by about 60%. Traps baited with synthetic phenols yielded similar numbers of G.pallidipes and significantly more G.longipennis than those baited with natural cow urine. The latter difference was not apparent when octenol was also used, so cow urine was retained as one of the odour baits in preference to the imported phenols. Although octenol increased catches of G.pallidipes by only about 30%, catches of G.longipennis were increased 2-4-fold, making it a very useful attractant for the latter species. The cost of the trap/odour-bait system was estimated to be US$8.5 per unit per annum. The economics of this method of tsetse control are discussed.

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 km 2 , 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.

No abstract

Studies were carried out at Nguruman, south-west Kenya to develop an effective trap/odour bait system that could be used for sampling and possibly controlling the tsetse Glossina longipennis Corti. Neither acetone nor cow urine increased trap catches significantly when used alone, but together they increased catches by about four to five times. Used with a target and electric screens, acetone with p-cresol, 3-n-propyl phenol and 1-octen-3-ol gave a significantly higher index of increase than did acetone and cow urine. The use of odour baits did not affect the age composition of the catch. The standard F3 trap was about three and a half times more effective for females than was the biconical trap and about eight times more effective when used without its blue floor. The NG2B was the best of the NGU series of designs, and caught about four times more females than did the biconical trap. Neither the F3 nor the NG2B caught significantly more males than the biconical trap. The NG2B caught a significantly higher proportion of parous female flies than the biconical. Either the F3 or the cheaper NG2B, baited with acetone and cow urine or phenols, is recommended as a sampling tool for G. longipennis. Electric screen experiments showed that the NG2B caught less than 10% of the flies that approached it. Despite this, it might still be effective for control of G. longipennis given the high mobility of this species and the consequent likelihood of encountering traps.

During translocations of black rhinoceros (Diceros bicornis Linnaeus) in Kenya, we studied the relationships between the rhinoceros and biting flies. In trapping experiments, rhinoceros waste products (urine or dung) were substituted for known attractants such as cow urine, l-octen-3-ol or acetone. Catches of Glossina pallidipes Austen, Glossina longipennis Corti, Stomoxys spp., and Haematopota spp. were not affected by these substitutions. NG2G and Vavoua traps sited near captive animals caught similar numbers and kinds of flies as traps set without animals. Any minor attractive properties of rhinoceros odours were probably due to the presence of known attractants such as 4-cresol and 3-n-propylphenol, which were confirmed to be present through gas chromatography-mass spectroscopy. In feeding trials with laboratory-reared tsetse, Glossina brevipalpis Newstead and Glossina morsitans centralis Machado fed well on immobilized animals, whereas G. longipennis fed reluctantly. Catches of G. brevipalpis were doubled in one trapping experiment when rhinoceros urine was used as odour bait. Philoliche spp., Haematopota spp. and other Tabanidae fed on captive rhinoceroses. Many species of Stomoxyinae were associated with rhinoceroses. Of these, the most frequent association was with Rhinomusca dutoiti Zumpt, a species found previously only in South Africa.