Autumn control of aphid pests of tree and bush fruit crops

Abstract: The aphid species that are significant pests of tree and bush fruit crops in Europe are almost all host-alternating. They spend the autumn, spring and early summer on their winterwoody tree/bush fruit host but migrate to a herbaceous host in summer. In the autumn, there is a return migration to the winter woody host by males and pre-sexual females (gynoparae), the latter producing sexual females (oviparae) which mate with the males and lay overwintering eggs on the bark. The normal strategy to control aphid pests is to apply an aphicide in spring shortly after the eggs have hatched to avoid the subsequent development of damaging colonies, which cause severe curling of leaves on shoots and stunting. Work on apple, raspberry and blackcurrant is reported, which has shown that good control of all the important aphid pests of these crops can be achieved by autumn application of an aphicide timed to kill the returning winged forms before egg-laying occurs. The advantages of autumn application are that the aphids are vulnerable to direct interception by sprays and that pesticide residues on fruit due to aphicide application do not occur. Possible methods for gauging the size and timing of the autumn migrations to rationalise the use of autumn aphicide sprays, including suction and sex pheromone trapping and surveying the incidence of gynoparae and oviparae on trees in the autumn, are discussed.