Studies of Crop Loss following Insect Attack on Cotton in East Africa

Abstract

The loss of crop following insect attack on cotton was studied in 1950–54 at the Cotton Research Station, Namulonge, which is situated in the elephant-grass zone of Uganda, in which the principal pest of cotton was originally considered to be Lygus vosseleri Popp. In 1953, the main invasion of cotton by Lygus occurred during September and October, originating from cultivated crops of black gram (Phaseolus mungo) and sorghum and from the wild perennial legume, Pseudarthria sp., which earlier workers had considered important. Trials in this zone have demonstrated, over a number of years, that early June is the optimum date for sowing cotton, although such sowings receive the heaviest attack by L. vosseleri. Experiments to determine the maximum loss of yield due to Lygus should therefore be made with cotton sown at this time. Bollworms are also important pests, notably Heliothis armigera (Hb.) and Earias spp., their attacks following those of Lygus and being heaviest in October–November.