Rehman, S.U. 1996 . Residual effects of pesticides on parasitism by Aphytis holoxanthus DeBach (Hymenoptera: Aphelinidae) on Florida red scale Chrysomphalus aonidum. Ph.D. Thesis; University of Florida 88 pp.

Notes: [Ph.D. Thesis; Harold W. Browning, Advisor.] Aphytis holoxanthus Debach is an important biological control agent of Florida red scale. Laboratory and field tests were conducted to quantify the mortality of this hymenopterous parasite caused by field residues of carbaryl and dicofol. Behavior and mortality of adult Aphytis holoxanthus on carbaryl treated 'Hamlin' orange leaves were related to quantities of dislodgeable pesticidal residues over time as field weathering of residues progressed. Our data showed that field weathered carbaryl residues killed A. holoxanthus for a period of up to 22 d post-treatment under spring conditions in Florida. Dicofol residues, on the other hand, were less toxic to the adult parasites. In another laboratory study, the rates of contact of A. holoxanthus with different carbaryl deposit patterns varied significantly (F = 13.16; df = 11; P $<$ 0.0001). The rate of contact was highest on leaf discs containing 20 deposits with and without carbaryl, while leaf discs having 2 large deposits of the same total volume (20 $mu$l) resulted in lower contact rates. The field study which was designed to understand the disruption of the host-parasite relationship by carbaryl and dicofol spray applications revealed that the mean survival rate of 3rd instar nymphs and gravid females on leaf samples was higher in the carbaryl treatment than in the dicofol and control treatments due to lower rates of parasitism. There was no significant difference in survival of 3rd instar nymphs and gravid females between the dicofol and control treatments. In September, the parasitism of FRS was significantly higher in the control and dicofol treatments than in the carbaryl treatment. Fruit infestation likewise was highest in the carbaryl treatment followed by the dicofol and control treatments. The likelihood ratio chi square test showed significantly lower fruit infestation and fruit drop in the control treatment than in the carbaryl and dicofol treatments.