OVIPOSITION ON VEGETABLES BY BEMISIA-TABACI (HOMOPTERA, ALEYRODIDAE) - TEMPORAL AND LEAF SURFACE FACTORS

Selection of ovipositional site of the sweetpotato whitefly, Bemisia tabaci (Gennadius), strain B, was studied under field, greenhouse, and laboratory conditions on early vegetative growth of commercial cultivars of 10 vegetable crops: cantaloupe (Cucumis melo L.), cucumber (Cucumis sativus L.), eggplant (Solanum melongena L.), bell pepper (Capsicum annuum L. ssp. annuum), collard (Brassica oleracea ssp. acephala de Condolle), cowpea (Vigna unguiculata (L.) Walpers ssp. unguiculata), snap bean (Phaseolus vulgaris L.), summer squash (Cucurbita pepo L. ssp. melopepo), tomato (Lycopersicon esculentum Miller), and watermelon (Citrullus lanatus (Thunberg) Matsum. & Nakai ssp. lanatus. Feeding and oviposition started on the cotyledon stage and populations of immature B. tabaci increased over time on all crops in field and greenhouse trials. On most plants, from 90 to 95% of the eggs were laid on the lower surface, with no definitive change over time or among leaves of a given crop. In a laboratory choice test using detached leaves facing downward, the lower leaf surface of cantaloupe, squash, and watermelon, was preferred for oviposition as compared with the upper surface. However, the upper surface was preferred in cowpea. There was no preference for egg-laying between leaf surfaces on the six other vegetables in the laboratory. Four crops, cantaloupe, cowpea, snap bean, and squash were evaluated for whitefly geotropic response for oviposition, and there was a strong negative response.