At least three species of Aphis attack the Apple: (1) the Leaf-curling Aphis (Aphis pomi); (2) the Rose Leaf-curler (Aphis sorbi); and (3) the Green-shoot Aphis (Aphis fitchii).

The former is by far the worst Apple species and is said to live solely on apple. The black eggs are found in masses in winter on the year's growth of wood. In spring they hatch into small lice which spread out over the leaves. Soon they grow into wingless viviparous females of a slaty and mealy appearance, and these produce quantities of living young, which very soon are mature and ready to produce others. These wingless aphides cause the leaves to curl up and fall off, and as they also puncture the shoots the latter become deformed. Later in the summer winged broods appear and fly off. In autumn, about the beginning of October, they return and produce yellowish young, which become oviparous females and lay the ova on the shoots.

The Rose Leaf Aphis causes the curled leaves to become bright red and yellow. This species also lives on Hawthorn. The Stem Aphis is green and does not curl the leaves, mainly collecting in early summer on the shoots and below the leaves and in the blossom. It migrates between the Apple and various grasses.

Ants carry all these aphides from place to place and are always found in company with them.

Not only does Aphis pomi damage foliage and shoots, but in bad cases the fruit is attacked and deformed.

Treatment

Treatmentconsists of heavy washings with soft soap and quassia or nicotine wash. If the former, it must be done before the leaves are much curled, as the wash will not enter the curled foliage; nicotine will, however, penetrate into the crevices and curls. Much good will also be done by heavy spraying with the same in autumn, to kill the egg-laying brood under the leaves.

All prunings should be burnt in winter, as many eggs are thus destroyed.