a1 ODA/IPMI Tsetse Project, c/o Tsetse and Trypanosomiasis Control Branch, Harare, Zimbabwe
a2 Natural Resources Institute, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK
a3 Tsetse and Trypanosomiasis Control Branch, Harare, Zimbabwe
a4 Regional Tsetse and Trypanosomiasis Control Project for Malawi, Mozambique, Zambia and Malawi, Harare, Zimbabwe
Methods for dispensing tsetse attractants using sealed polyethylene sachets and bottles were studied in the laboratory and field. 1-Octen-3-ol (octenol), 4-methylphenol and 3-n-propylphenol were dispensed singly or as blends from sachets 25–200 cm2 in surface area and with a wall thickness of 0.06–0.32 mm; butanone was dispensed from polyethylene bottles. The release rates of attractants, assessed gravimetrically or by GC analysis of volatiles released, were independent of the amount present. The rates were related directly to surface area, inversely related to wall thickness and increased exponentially with temperature. With blends of the attractants, the release rates of the two phenols were directly proportional to the concentration present, but that of octenol showed an exponential dependence. A similar exponential effect was seen with blends of the attractants and an involatile diluent. For mixtures of chemicals, the ratio of the released components was not affected significantly by temperature, sachet size or wall thickness. Release rates from polyethylene sachets and bottles in the field varied 100-fold according to temperature differences related to the time of day, season, and degree of insolation. Day-degree models to predict the losses of attractants from a polyethylene sachet in shade or in full sunlight were highly correlated (r2 = 0.84 and 0.81 respectively) with observed losses. The practical implications of these findings are discussed.
(Accepted October 23 1996)
c1 Natural Resources Institute, Central Avenue, Chatham Maritime, Kent, ME4 4TB, UK.