Trials of Spraying and Cultural Practices on Cotton in Uganda. II. Use of Extended Protection

Abstract

SUMMARYTrials are described comparing the effects of applying four, eight and 12 sprays of various insecticides on control of Heliothis armigera Hub, and Earias biplaga Wlk., and the consequent effect on yield and quality of seed cotton produced. Yields of unsprayed cotton ranged from 300–900 kg/ha, while four sprays of DDT gave 1000–1200 kg/ha. Increasing the number of sprays to 12, using three insecticides (DDT, endosulfan and carbaryl) gave increments of 300–600 kg/ha over the standard four spray treatment. Eight sprays gave smaller but significant yield increases, and endosulfan, dicrotophos and carbaryl were particularly promising in such regimes. A mixed DDT/phenthoate spray was not superior to DDT used alone. Spraying reduced the percentage of stained cotton.