An experiment in the use of discriminative clearing for the control of Glossina morsitans Westw. in Ankole, Uganda

The situation following different degrees of discriminative clearing against G. morsitans Westw. was examined in eastern Ankole District, Uganda. In one area, where the treatment had been more intensive, the fly density was low, and it seemed that the population might be maintained by immigration from an adjacent area to the west, where treatment had been less intensive and in parts of which fly density was relatively high. The application of more intensive discriminative clearing of the fly's concentration sites to the western area, together with completion of the treatment of the eastern, failed to result in any marked effect on the tsetse population except as regards its distribution. Before this intensive clearing, concentrations of G. morsitans occurred in a double-storey vegetation type, the chief component of the upper storey of which consisted of Acacia gerrardii. After the upper-storey trees in this were felled, concentrations were found in groups of tall Acacia hockii, 12–18 ft. high, which had appeared to be of little importance to the fly before clearing. A year after the treatment of the western area there was no apparent reduction in fly density. The feeding habits and rate of utilisation of reserves of the flies showed no significant change as a result of clearing.It seems that the failure of the discriminative clearing régime applied in this area, compared with the effect produced by less intensive clearing elsewhere in Ankole, is due to the presence in this area alone of the groups of tall A. hockii.