Nymphal survival and movement of crawlers of Bemisia argentifolii (Homoptera: Aleyrodidae) on leaf surfaces of selected vegetables

Abstract

Bemisia argentifolii Bellows and Perring generally feeds and develops on the under leaf surface of most host plants, but in excess of 50% of the immature population may be found on the upper surface of some host species. This study determined the influence of leaf surface on survival of immature B. argentifolii and the likelihood of movement by the crawler (1st instar) from the upper (adaxial) leaf surface on selected vegetable hosts. Laboratory tests were conducted on 5 vegetables: cantaloupe, Cucumis melo L.; collard, Brassica oleracea ssp. acephala de Condolle; cowpea, Vigna unguiculata (L.) Walpers ssp. unguiculata; pepper, Capsicum annuum L. ssp. annuum; and tomato, Lycopersicon esculentum Miller. Survival to the 1st instar was high (85-95%) on the upper leaf surface on all hosts. Survival to the adult stage was similar between whitefly nymphs on the upper and lower leaf surfaces within each host crop, except more survived on the lower surface of cowpea compared with the upper surface. Movement of the crawlers from the upper to the lower surface was high on pepper (≃80%), cantaloupe (≃55%), and cowpea (≃55%). Conversely, less movement to the lower surface was observed on collard (≃18%) and tomato (≃30%). The impetus to move from the upper surface appears primarily a response to feeding and tactile cues instead of responses to geotropic or phototropic stimuli.