Relationship of silverleaf whitefly population density to severity of irregular ripening of tomato

The silverleaf whitefly (Bemisia argentifolii Bellows & Perring) is an impo rtant pest of tomatoes in Florida and elsewhere. Associated with population s of the whitefly is an irregular ripening disorder of fruit characterized by inhibited or incomplete ripening of longitudinal sections of fruit and b y an increase in the amount of interior white tissue. Experiments were cond ucted during the spring and fall tomato production seasons of 1995 and 1996 to elucidate the relationship of nymphal and pupal density with severity o f the disorder. Insecticides or insecticide combinations were applied at pr edetermined densities of whitefly nymphs and pupae and the subsequent sever ity of the disorder was rated separately for external and internal symptoms on red ripe fruit harvested weekly. Expression of irregular ripening sympt oms, especially external symptoms, were correlated positively to the densit y of whitefly nymphs and pupae (number(.)10(-1) terminal leaflets on the se venth to eighth leaf from the top of a main or lateral stem) increased. Exp ression of external symptoms tended to be better correlated with whitefly d ensity when symptom severity was rated 1 and 3 weeks after estimating white fly density for the spring and fall seasons, respectively. Expression of in ternal symptoms tended to be more consistently correlated with whitefly den sity when symptom severity was rated 2 and 3 weeks after estimating whitefl y density for the spring and fall seasons, respectively.