Submitted to: Environmental Entomology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: November 15, 1998
Publication Date: N/A
Interpretive Summary: The silverleaf whitefly (= B-strain sweetpotato whitefly) is an important pest of vegetable crops and is difficult to manage. To formulate more effective management practices, these studies of whitefly population development were conducted. The insect generally feeds and develops on the underside of leaves of many plants, but on some plant species over 50% of the eggs and nymphs are found on the upper leaf surface. This study examined the influence of leaf surface on nymphal survival and the likelihood of nymphal movement from the upper to the lower leaf surface of several vegetable crops. Laboratory tests were conducted on cantaloupe, cowpea, collard, bell pepper, and tomato plants. Egg hatch was high (85-95%) on all crops. Survival to the adult stage was similar between nymphs on leaf surfaces of each crop, except for cowpea where more survived on the lower than the upper leaf surface. The only movement by the nymphs occurs during the early period of the first immature stage. Movement from the upper surface was great on pepper (80%), cantaloupe (55%), and cowpea (55%), but less occurred on collard (18%) and tomato (30%). No influence of gravity and little influence of light were observed on nymphal movement. Movement was primarily in response to feeding and feel of the different plants. This information will help in understanding population development and in formulating improved management practices.
Technical Abstract: Bemisia argentifolii generally feeds and develops on the under leaf surface of most host plants, but on some host species in excess of 50% of the immature population may be found on the upper surface. This study determined the influence of leaf surface on survival of immature B. argentifolii, and the likelihood of movement by the crawler (first instar) from the upper (adaxial) leaf surface on selected vegetable hosts. Laboratory tests were conducted on cantaloupe (Cucumis melo L.), collard (Brassica oleracea ssp. acephala de Condelle), cowpea (Vigna unguiculata (L.) Walpers ssp. unguiculata), pepper (Capsicum annuum L. ssp. annuum), and tomato (Lycopersicon esculenum Miller). Survival to the first instar was high (85-95%) on the upper leaf surface on all hosts. Many crawlers moved from the upper to the lower surface on pepper (80%), cantaloupe (55%), and cowpea (55%). Less movement to the lower surface was observed on collard (18%) and tomato (30%). The impetus to move from the upper surface was apparently primarily a response to feeding and tactile cues instead of responses to geotropic or phototropic stimuli. Survival 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.