Aphis pomi

Scientific Name Aphis pomi (De Geer)
Common Names English: Green apple aphid; German: Grüne Apfelblattlaus; French: Puceron vert du pommier; Spanish: Pulgon verde del manzano; Italian: Afide verde del melo
Description The body is luscious green, and also yellow-green later in summer, about 1.5 to 2.5 mm (0.06-0.09 inch) in length and pear-shaped. The legs, antennae and siphunculi are dark, almost black.

Biology

Damage

A. pomi prefers the undersides of young leaves as feeding sites. It is mainly found on young shoots or water sprouts. Leaves carrying colonies may roll and curl, but will not discolor. The aphid occasionally feeds on immature apples, which then become malformed. Heavy infestation, especially of young trees, can lead to stunting, and in extreme cases to the shedding of leaves: thus considerable damage can occur in nurseries, in which plants at the susceptible age may become permanently deformed. Older trees suffer considerably less.
The honeydew produced by the insects in copious amounts promotes the growth of sooty molds. On leaves, this may impede photosynthesis, thus affecting yield; fruits become unsightly and their market value is reduced. Most damage occurs in the spring in apple orchards, when many rapidly-growing shoots are available and natural predators have not yet emerged in substantial numbers.

Lifecycle

A. pomi can complete its entire life cycle on the same plant species: it does not have to change hosts. Otherwise, its biology is similar to that of most other aphid species.
The first nymphs hatch from the winter eggs in the spring, as the apple buds open. These females are the founders („fundatrices“) of the aphid colonies: after 2-3 weeks, they start to produce offspring, several dozen each, which in turn are all female and parthenogenetic. This also applies to the following summer generations. These „virginoparae“ are initially wingless, but winged forms occur later and migrate to other trees, or become transported over many kilometres by wind currents. In the autumn, „sexuales“ of both sexes appear. After mating, winter eggs are deposited in large batches - which is unusual for an aphid species - and can often be found at the base of buds.
During the summer, populations can build up very quickly: each female can produce about 50-100 offspring, which, in turn, are able to propagate after 1-2 weeks.
Colonies of A. pomi are very often carefully attended by ants.
This aphid is found in Europe, parts of the Middle East and in North America.

Occurrence

Agricultural Importance

A. pomi normally causes little injury except in nurseries and on young trees. Population densities can, however, increase rapidly if natural antagonists appear late or are ineffective, e.g. because of weather conditions or an unusual intensity of ant attendance. In this case, damage can be economically significant.

Control

Integrated Crop Management

Careful pruning and minimized N-fertilization will reduce water sprouts and thereby remove favorable feeding sites for the aphids.
Antagonists play an important role in regulating this pest, so pesticides should be chosen and applied with care.

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