Separation of three common hover fly predators of woolly apple aphid based on the exochorionic sculpturing of eggs

Abstract

The woolly apple aphid, Eriosoma lanigerum (Hausmann, 1802) (Hemiptera: Aphididae), is a cosmopolitan, indirect pest of cultivated apple, Malus domestica (Borkh.) (Rosaceae), (Baker 1915) that can colonize both the roots and arboreal portions of trees and adversely affect the growth, vigor, and productivity of the host (Weber and Brown 1988; Brown and Schmitt 1990; Brown et al. 1991, 1995). Historically, the solitary endoparasitoid Aphelinus mali (Haldeman, 1851) (Hymenoptera: Aphelinidae) has been considered the most important biological control agent for E. lanigerum in many, but not all, apple-growing regions (Yothers 1953; Nicholas 2000). The role of arthropod predators in regulating woolly apple aphid populations, particularly early in the growing season, has long been recognized (Dumbleton and Jeffreys 1938; Bodenheimer 1947; Nicholas 2000; Mols and Boers 2001) but has not been adequately addressed (Asante 1997).