METHODS FOR DISPENSING ODOR ATTRACTANTS FOR TSETSE-FLIES (DIPTERA, GLOSSINIDAE)

Methods for dispensing tsetse attractants using sealed polyethylene sa chets and bottles were studied in the laboratory and field. 1-Octen-3- ol (octenol), 4-methylphenol and 3-n-propylphenol were dispensed singl y or as blends from sachets 25-200 cm(2) in surface area and with a wa ll thickness of 0.06-0.32 mm; butanone was dispensed from polyethylene bottles. The release rates of attractants, assessed gravimetrically o r by GC analysis of volatiles released, were independent of the amount present. The rates were related directly to surface area, inversely r elated 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 o ctenol 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 a ffected significantly by temperature, sachet size or wall thickness. R elease 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 th e losses of attractants from a polyethylene sachet in shade or in full sunlight were highly correlated (r(2)=0.84 and 0.81 respectively) wit h observed losses. The practical implications of these findings are di scussed.