Ultra-low-volume Spray Application on Cotton in Malawi

Abstract

Farmers in Africa often have only one or two hectares of cotton and use conventional knapsack sprayers to apply insecticides in 56–224 1 water/ha; in Malawi farmers have obtained yields averaging 1000 kg seed cotton per hectare. As water supply is a major problem ultra-low-volume application with a small battery-driven spinning disc sprayer is being evaluated with encouraging results although costs are slightly higher than for conventional spray application. 25% carbaryl and 40% DDT to control Diparopsis castanea Hmps and Heliothis armigera Hbn respectively are applied according to assessments of insect populations by routine scouting, with dimethoate added as required as aphicide-acaricide. Spray is fed to the spinning disc at 0.5 ml/sec and swath width decreased from six to two rows during the season. On a two-row swath (1.8 m) when plants exceed 50 cm height, 2.5 1 of spray are applied per hectare.