Aircraft applications of insecticides in East Africa

Abstract

SummaryFollowing successful small-scale trials, an attempt was made, by aircraft application of insecticide, to eradicate Glossina morsitans Westw. and G. pallidipes Aust. from an isolated block of savannah woodland, approximately 11 sq. miles in extent, at Chungai in the Central Province of Tanganyika between July 1958 and January 1959. A single-engined aircraft, fitted with two belt-driven rotary-cage atomisers, was used to apply a 5 per cent, solution of γ BHC in power kerosene at a nominal dosage of 0·08 gal. per acre (0.04 lb. γ BHC per acre). Seven applications were made at approximately 28-day intervals, the time taken to complete an application varying from five to eight days. The operation failed to control the flies. Although each of the first two applications reduced the apparent density of G. morsitans by about 90 per cent, and that of G. pallidipes by a lesser, although still considerable, factor, later applications gave varying and often low mortalities, and the populations increased slowly for some time, the insecticide applications causing only temporary depressions in numbers. Numbers fell towards the end of the operation, but final reductions were only about 50 per cent, or less. Kills of female flies were low, and this undoubtedly led to the eventual failure.The low volume-dosage, a drop spectrum that possibly contained too few droplets of the required size, meteorological conditions, and biological factors that apparently favoured the survival of female flies are suggested as contributory elements to the low mortalities.Operational costs were considerably lower than in previous work.