Aphids on river birch attract ladybugs

lady bug

Immature ladybugs eat more aphids than their more familiar adult form.

Photo by Charlotte Glen
Published: Friday, May 10, 2013 at 02:27 PM.

River birch is a tough and adaptable native tree that is also a popular landscape plant throughout the south. If you notice some of the leaves on your river birch have become thickened, distorted, or discolored in the last few weeks don’t be alarmed. While caused by a type of aphid, these symptoms are not a sign of serious damage and can even be an indication of good things to come to your yard.

Understanding aphids

A common spring pest, aphids are small, soft bodied insects sometimes referred to as plant lice. Size wise, most aphids are little larger than a grain of rice. There are many different kinds of aphid and while most are green, you may find species that are yellow, orange, brown, red, or black, as well as covered in white wooly fluff. Like many pests, most aphid species are adapted to feed on a narrow range of plants and will not spread to everything in your yard.

Aphids feed on plant sap with straw shaped mouth parts. On ornamental plants, their feeding can cause leaves and stems to become twisted or distorted, but rarely leads to serious damage. As they feed aphids secrete honeydew, a sticky sweet substance that can attract ants and wasps. Black sooty mold, a harmless fungus, often grows on the honeydew, causing aphid infested plants to appear dirty or sooty. Black sooty mold does not damage plants and can be washed off with water or horticultural oil.

The specific type of aphid that feeds on river birch foliage is known as the spiny witch-hazel gall aphid. In the spring, this aphid feeds on river birch leaves. In early summer it moves on to witch hazel foliage, but will not infest any other type of plant. When spiny witch-hazel gall aphids feed on river birch the leaves become crinkled and discolored, with pink corrugated ridges. If you look on the underside of affected leaves you will see the aphids tucked into the ridges.

River birch trees will shed most of the leaves these aphids feed upon, but they quickly grow new leaves and no lasting harm is done to infested trees. This type of damage is often referred to as cosmetic, since it causes no serious injury, and does not require treatment. Even better, the aphids that cause this damage attract hundreds of ladybugs and other beneficial insects to your yard that will persist long after the aphids have gone.

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