Short-term Effects of Three Insecticides on Predators and Parasites of the Citrus Blackfly 12

The effects of 3 organophosphate insecticides, acephate, malathion, and methidathion, on predators and parasites of Aleurocanthus woglumi Ashby, the citrus blackfly, were studied under field conditions. Acephate and malathion are currently the insecticides used in the joint federal-state citrus blackfly eradication program and methidathion is currently one of the insecticides commonly used by commercial citrus growers in Florida. Highly significant reductions ( P <0.01) in numbers of the parasite Amitus hesperidum Silvestri (Hymenoptera: Platygasteridae) were observed following single applications of malathion and methidathion although a single treatment of acephate did not produce significant ( P >0.05) reduction. Numbers of the predator Delphastus pusillus (Le Conte) (Coleoptera: Coccinellidae) were significantly ( P <0.05) reduced following a single treatment of methidathion, while no significant reductions were noted following exposure to single treatments of either acephate or malathion. The general predators (spiders, Chrysopidae, and Coccinellidae excluding D. pusillus ) were grouped together and treated as one biological unit. There was no significant change in the general predator complex noted after single applications of either acephate, malathion, or methidathion. Two laboratory bioassays, one using leaves dipped in insecticide suspensions and one using leaves sprayed with 3 compounds, indicated that emergence of A. hesperidum is not significantly reduced by one treatment of acephate but is reduced by one treatment of either malathion or methidathion.