An experiment on the incidence and spread of angular leaf-spot disease of cotton in Uganda

SUMMARY. Experiments on the incidence and spread of the angular leaf-spot disease of cotton, carried out at two centres in Uganda, are described. Treatment of the seed by sterilisation with sulphuric acid and mercuric chloride resulted in a reduction in the amount of the disease throughout the season. Treatment of the seed with a bactericidal dust had a significant effect on total germination, the plots sown with this seed having a greater number of plants at the end of the season, independently of those killed by the disease. Primary infection was almost entirely limited to plots sown with seed inoculated with the organism. Spread of the disease occurred in a direction down the slope of the ground and along the lines of surface wash. The implications of the experiment are discussed and proposals made for modifications in technique.