Development of odour-baited traps for Glossina swynnertoni (Diptera: Glossinidae)

Three new prototype traps, (S1–S3), were developed during studies of the behavioural ecology of Glossina swynnertoni Austen in Kenya and Tanzania. The traps were compared in latin square experiments relative to the regular biconical trap as a standard and a selection of other conventional tsetse traps. Observations were also made on fly behaviour in the vicinity of traps using electric nets and sticky materials. When baited with acetone and 1-octen-3-ol, the S1 trap was 3.5 times as effective in catching G. swynnertoni in Kenya as the biconical trap. In Tanzania, the relative performance of the S1 and biconical traps differed; also, both traps were found to be inferior to an all-black, sticky 1-m2target. A second prototype (S2) performed slightly better than the biconical trap, but was still inferior to the black target. The final prototype (S3) was 2.9 times as effective as the biconical trap and performed as well as the black target. The potential for further improvement of traps for capturing G. swynnertoni and flies of the G. morsitans Westwood group is discussed.

The responses of Glossina pallidipes and G. longipennis (Diptera: Glossinidae) to odour-baited traps and targets at Galana Ranch, south-eastern Kenya

Four designs of trap, all made from identical material, were compared at Galana Ranch, south-eastern Kenya, as sampling devices for Glossina pallidipes Austen and G. longipennis Corti. The NG2G and Epsilon traps caught more than twice as many female G. pallidipes as the biconical trap, and the F3 was intermediate. A similar, pattern was observed for males, although the differences were smaller, and not significant. The NG2G, Epsilon and F3 traps all caught approximately twice as many male and female G. longipennis as the biconical trap. Acetone (500 mg/h) significantly increased trap catches of G. pallidipes, and there was a synergism between acetone and 4-methylphenol (0.8 mg/h). There was little or no effect with 1-octen-3-ol (0.8 mg/h). Acetone, 1-octen-3-ol, and 4-methylphenol all increased trap catches of G. longipennis, and there were no synergisms among them. Cow urine (850 mg/h) increased the catches of both species in traps baited with acetone and 1-octen-3-ol, although not significantly for G. longipennis. There was no effect with 3-methylphenol (0.8 mg/h). The addition of 3-propylphenol to traps baited with acetone, 1-octen-3-ol and 4-methylphenol had no effect on the catches of either species. For G.pallidipes, a combination of acetone, 1-octen-3-ol, 4-methylphenol and 3-propylphenol was calculated to have a catch index of 6–8 over unbaited traps, a value lower than that reported for Zimbabwe and Nguruman, Kenya, and greater than that reported for Somalia. The catches of G. longipennis were approximately three times higher on electrified targets than in F3 traps, although there was no difference in the catch of G. pallidipes.

Traps and odour baits for the tsetse fly, Glossina longipennis (Diptera: Glossinidae)

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.

The responses of Glossina pallidipes Austen (Diptera: Glossinidae) to odourbaited traps and targets in Somalia

Studies were carried out at Jilaal Moogi, south-eastern Somalia, of the responses of Glossina pallidipes Austen to traps and targets. F3 traps caught three times as many tsetse as a biconical trap. Baiting F3 traps with acetone (released at 5–50 000 mg/h), butanone (10–50 mg/h) or octenol (0·05–5 mg/h) either alone or as mixtures did not affect the catch significantly. The catch was increased by 1·6 times (P<0·05) by releasing a mixture of 4–methylphenol (at 0–2 mg/h) and 3-n-propylphenol (0·04 mg/h), and by four times by releasing a mixture of acetone (500 mg/h), octenol (0·5 mg/h) and the two phenols. Baiting a target enclosed in an electric net with the combination of acetone, octenol and phenols increased the catch only 1·3 times, (P>0.05). Baiting an electric net plus target with natural ox odour increased the catch 1·8 times (P<0·05). A pthalogen blue (peak reflectivity = 40% at 450 nm) target caught 1·7 times as many tsetse as a black target (P<0·01) and a standard blue (reflectivity = 29%) target caught 7·4 times the catch of a yellow one (P<0·001). The results are compared with published data from Zimbabwe, Kenya and Mozambique, and it is noted that the level of response of G. pallidipes in Somalia to host odours is lower than elsewhere.

A comparison of various traps for Glossina spp. (Glossinidae) and other Diptera

Several new traps were designed and tested against Glossina morsitans morsitans Westwood and G. pallidipes Austen in Zimbabwe. The best of the new traps, the F2, was three times as effective as a beta trap and ten times as effective as a biconical trap for G. pallidipes. A white biconical trap was only half as effective as an F2 trap for females of G. m. morsitans. The catch of males of G. m. morsitans was similar in all traps. The F2 trap was up to ten times as effective as a beta trap for Stomoxyinae. Catches doubled when acetone was released at 0·5 or 5·0 g/h near the traps. Catches from traps made of white cloth declined by 90% as the cloth yellowed with exposure but were restored when the cloth was painted white.

The improvement of traps for tsetse flies (Diptera: Glossinidae)

Based on previous studies of the trap-orientated behaviour of Diptera, a variety of new traps was designed to maximise the speed and probability of capturing Glossina morsitans morsitans Westw. and G. pallidipes Aust. arriving near traps, and to minimise the probability of capturing other flies. In Zimbabwe, catches were made with these traps in the presence and absence of carbon dioxide and acetone as odour attractants, leading to the identification of a simple trap for which the probability of capturing Glossina spp. was up to twice as great as it was for a standard biconi-cal trap, and for which the probability of capturing other Diptera was very much less than it was for the biconical trap. The probability of capture by the simple trap was 100% for G. pallidipes, 51% for G. m. morsitans, 6% for Stomoxyinae and 1% for non-biting Muscidae. Half the tsetse that arrived near the simple trap were captured within 5 min of arrival. The number of tsetse that contacted simple targets designed to expose flies to insecticide amounted to 32–263% of the catches of a biconical trap. The use of traps and targets for tsetse control, and the procedures for trap improvement, are discussed.