The black peach aphid (Brachyeauclus persienecola), which is found in most peach-growing districts, attacks both the roots and the above-ground portions of the trees. Although the peach is its main food-plant, apricots growing on peach stocks, plums, nectarines and almonds may also be infested.

While aphids may be found on the roots throughout the year, the aboveground portions of infested trees are generally free from late December to early March, as with the arrival of hot weather the aphids move back to the roots.

Wingless forms, in all stages of development, are to be found on the roots of the trees, at the junction of the trunk and main roots, and on the feeder roots, at a depth of about twelve inches, and from twelve to eighteen inches from the butt.

The lateral growth, which will carry the next season's crop, becomes infested from late March to early April, depending upon the weather. Mild, moist conditions appear to favour development.

During spring the aphids, if numerous, migrate to the blossoms and suck the sap from the flower parts, or from the young fruit which has just set, and this results in the shrivelling and shedding of young fruits.

After the leaf-buds burst, the aphids on heavily infested trees swarm on to the leaves, causing them to shrivel and, finally, to drop.

Wingless aphids predominate at all times, but during September and October it is usual for winged forms to develop in the colonies and they appear to be the principal means of distribution throughout individual blocks.

The
black peach aphid is not known to lay eggs, all the individuals being females which produce living young.