Increases in Florida red scale populations through pesticidal elimination of Aphytis holoxanthus Debach in Florida citrus

Eased on a laboratory study, a field study was designed to determine if the host-parasite relationship of Florida red scale and Aphytis holoxanthus co uld be disrupted in Florida by carbaryl and dicofol pesticide applications. The mean survival rate of third instar nymphs and gravid females on leaf s amples was higher in the carbaryl treatment than in the dicofol and control treatments due to lower rates of parasitism. There were no significant dif ferences in the survival of third instar nymphs and gravid females in the d icofol and control treatments. In September, parasitism of Florida red scal e was significantly higher in the control and dicofol treatments than in th e carbaryl treatment, and September fruit infestation by Florida red scale was highest in the carbaryl treatment, followed by those in the dicofol and control treatments. Higher fruit infestation in the carbaryl treatment (26 %) than in the dicofol (9%) and control (7%) treatments did not result in h igher fruit drop. This is the first Florida study that shows that pesticide use can increase Florida red scale populations and it confirms previous la boratory results. (C) 2000 Academic Press.