Woolly apple aphid (Eriosoma lanigerum Hausm.).
Information is reviewed from the world literature on the morphology, biology, natural enemies and control of Eriosoma lanigerum and on the damage that it causes on apple in Italy, with occasional attacks on pear and other Rosaceae. The aphid attacks the woody parts of the tree, and heavy infestations may result in the formation of swellings and wounds that permit the entry of the fungi Nectria ditissima and N. galligena, which produce cankers. The apple variety Starking was one of the most susceptible to E. lanigerum. One method of preventing the development of reservoir populations of the aphid underground is to use rootstocks of resistant cultivars. Populations of the aphid can also be kept down by encouraging the activity and spread of the parasitoid Aphelinus mali, which was originally imported from the USA but which has become acclimatized in Europe. Recommended chemical treatment consists of yellow oil [DNOC in oil] applied in the winter against hibernating immature forms of the aphid and other apple pests, especially on the collar or on any cankers; this is followed by sprays of systemic products such as vamidothion, phosphamidon or methyl-demeton [demeton-methyl] during the growing period of the tree but especially after flowering, when predators are less abundant.