Eriosoma lanigerum (Hausmann)
Common name: wooly apple aphid, spirea aphid.
Geographical distribution: Of Nearctic origin, the pest has a wide geographical distribution and occurs throughout the Middle East.
Morphology: The color of the apterate viviparous female is a purple-brown. It is covered by white, waxy filaments that are secreted from dermal plates, which are arranged in longitudinal rows on the posterior part of the body. The compound eyes consist of 3 facets each. The head and thorax of the alate viviparous female are brown-black, and the abdomen is brown. The siphunculi are reduced to a pair of rings on the posterior dorsum of the abdomen.
Life Cycle: Eriosoma lanigerum is an exotic species in the Middle East. In North America its primary host is the American elm tree (Ulmus americana Linnaeus). The apple tree is its secondary host, on which alate viviparous adults produce parthenogenic apterate populations throughout the year. Densely packed populations are formed on both arboreal and subterranean parts of apple trees. Viviparous parthenogenic reproduction is the norm in the Middle East, in contrast to regions with more temperate climates, where diapause eggs are laid in the fall on the primary host by reproducing females. There are no records of the sexual reproduction of E. lanigerum or about its dispersal by winged forms wherever the primary host is absent, except in rare situations, in temperate countries, where diapause eggs are laid on apple.
Economic importance: The woolly apple aphid can reduce crop production, causing severe damage to young nursery trees or newly planted orchards. Colonies on stems or roots induce the proliferation of nonfunctional xylem, with consequent disruption of water transport. This insect is considered a quarantine pest and its presence in or on imported fruit or plant material is prohibited in many countries.
Plant resistance: Not all apple cultivars are equally infested by the pest. A North American cultivar (Northern Spy) has been regarded as highly resistant, perhaps due to the very high ratio of phenols/amino acids in its phloem. Resistance-breaking biotypes of the woolly apple aphid have recently been reported.
Subterranean populations may be infected by soil-borne entomopathogenic fungi. The aphelinid parasitoid Aphelinus mali Haldeman has been introduced in order to control the pest and had become established in many countries, including Israel and Cyprus.
Swirski, E. and Amitai, S. 1999. Annotated list of aphids (Aphidoidea) in Israel. Israel Journal of Entomology 33: 1-120.
Cohen, H., A. R. Horowitz, D. Nestel, and D. Rosen. 1996. Susceptibility of the woolly apple aphid parasitoid, Aphelinus mali (Hym. Aphelinidae), to common pesticides used in apple orchards in Israel. Entomophaga 41: 225-233.