Fruits Affected

Apple

Also See

This aphid, Erisoma lanigerum, is a native to North America. The WAA or "woolly" may occur on the above-ground portions or on the roots of the apple tree. Aphids inhabiting above-ground parts of the apple tree are most common in mid-summer and fall.

Symptoms

Cottony masses at the base of leaves; galls on shoots; general decline in tree health. Organic Treatments In many growing areas, WAA is scarcely an issue as their populations are controlled by natural predators and climate. In areas where trees are especially vulnerable to this pest, the first line of defense is to use WAA resistant rootstocks: Most of the Geneva stocks are resistant (G.16  is not), M.M.106, and M.M.111.

Conventional Treatments

Same as organic treatments.

Insect Cycle

This aphid, Erisoma lanigerum, is a native to North America. The WAA or "woolly" may occur on the above-ground portions or on the roots of the apple tree. Aphids inhabiting above-ground parts of the apple tree are most common in mid-summer and fall. Shoots and watersprouts are their favorite places to hang out. Overwintering colonies may be found in old pruning scars but the roots of the tree are their winter home of choice. The aphids are covered with long white waxy filaments that give the colony their distinctive woolly appearance.

The newborn woolly is a pinkish nymph known as a "crawler," and it does not yet have its woolly coating. Once the nymph settles down to feed on the tree, it develops the woolly coating, and infestations can appear as cottony masses at the axils of leaves (where the leaf stem joins the branch stem). Populations will work their way down the tree to feed on the roots. Wherever they feed, woollies will, over time, cause galls (swollen enlargements, comparable to tumors or warts on animal tissue), and continuous feeding on the roots can stunt growth and kill a younger tree. The galls caused by woolly activity also provide an entry point for other diseases, especially perennial canker. Woollies can also infest the stem and calyx end of the apples. In varieties with an open calyx, aphids can even infest the apple core.

For more information, see Apple IPM for Beginners from Cornell University Cooperative Extension and the Cornell factsheet on Woolly Apple Aphid.