Effects of the malathion-bait mixture used on citrus to control Ceratitis capitata (Wiedemann) (Diptera: Tephritidae) on the Florida red scale, Chrysomphalus aonidum (L.) (Hemiptera: Diaspididae), and its parasitoid Aphytis holoxanthus DeBach (Hymenoptera: Aphelinidae)

Examples of Chrysomphalus aonidum (L.) from which the scale covers had been removed, were about six times as sensitive to malathion as intact insects (LC50s of 0·09% and 0·55%, respectively). These results indicate that the scale cover probably absorbed part of the insecticide. Immature stages of the external parasitoid Aphytis holoxanthus DeBach on C. aonidum were not affected by 0·13% malathion applied to the host. However, adults of the parasitoid, which were extremely susceptible, were exposed before or during emergence to lethal levels of the insecticide present in the host scale cover. The findings are discussed in the light of the adverse effects of malathion-bait sprays applied against Ceratitis capitata (Wiedemann) on beneficial insects, and failures of biological control of scale pests on citrus in Israel.