DETERGENTS AND PLANT-DERIVED OILS FOR CONTROL OF THE SWEET-POTATO WHITEFLY ON COTTON

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 cott on leaves reduced the number of adult sweetpotato whiteflies, Bemisia tabaci (Gennadius) by 69-91% and nymphs by 97-99%. Treatments of 0.5 a nd 1.0% Nirma and Surf, as well as 1.0% Wheel, applied with a foot-ope rated sprayer to cotton reduced the number of nymphs to an extent equa l to that of a 0.05% triazophos spray. Treatments of cottonseed oil an d neem oil (Neemark) at 0.5 and 1.0% applied with a foot-operated spra yer 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) w ith a nozzle tip at right angles to the wand. The short wand was easie r to use for spraying the undersides of leaves of mature cotton plants and took no more spray material and only slightly longer than 'over t he top' spraying. Results also confirmed that the undersurfaces of the leaves must be thoroughly wet with spray materials to obtain effectiv e whitefly control.