Detergents and plant-derived oils for control of the sweetpotato whitefly on cotton

Abstract Four common detergent powders marketed in India, Nirma, Rin, Surf and Wheel, at concentrations of 0.25, 0.5 and 1.0%, applied to single cotton leaves reduced the number of adult sweetpotato whiteflies, Bemisia tabaci (Gennadius) by 69–91% and nymphs by 97–99%. Treatments of 0.5 and 1.0% Nirma and Surf, as well as 1.0% Wheel, applied with a foot-operated sprayer to cotton reduced the number of nymphs to an extent equal to that of a 0.05% triazophos spray. Treatments of cottonseed oil and neem oil (Neemark) at 0.5 and 1.0% applied with a foot-operated sprayer were equal in effectiveness to a 0.05% fenpropathrin spray against both adults and nymphs. The time required for spraying and the amount of spray needed was compared using a standard wand [89 cm (35 inches)] with the nozzle at a 30 degree angle to the wand used both for ‘over the top’ ( Heliothis ) spraying and for spraying the undersides of the leaves, and a modified wand which was shortened to 36 cm (14 inches) with a nozzle tip at right angles to the wand. The short wand was easier to use for spraying the undersides of leaves of mature cotton plants and took no more spray material and only slightly longer than ‘over the top’ spraying. Results also confirmed that the undersurfaces of the leaves must be thoroughly wet with spray materials to obtain effective whitefly control.