Aphids are small, pear-shaped, soft-bodied insects that feed on plant sap. They are often found in large numbers, clustered on the underside of leaves or tender, new stems.

Aphids can cause leaves to yellow or wilt, but damage to trees and shrubs is not always obvious. It is common to notice a shiny, sticky material known as honeydew. You will find honeydew on the tops of leaves, branches, and other objects underneath the aphids.

In most cases, aphids have little impact on healthy, well-established trees. Even when large numbers are present, you can ignore aphids without worrying about the plants' health. As aphid numbers increase, they attract natural enemies, such as ladybugs, which help control aphids.

When aphids are numerous on young or unhealthy trees or shrubs, they can injure plants. When you need to control aphids, first try to knock them off with a hard stream of water. A heavy rainstorm gives the same results.

If you want to use an insecticide without harming natural enemies, try insecticidal soap. You can find this product in most gardening stores. This is very effective against aphids and has little impact on beneficial insects. However, it only affects the aphids it directly contacts so repeat treatments may be necessary. Also, do not spray insecticidal soap on tender, young leaves. It can damage the new leaves!

Other insecticides, including acephate-sold as Orthene™, and malathion, are also effective. However, if natural enemies, like ladybugs are also seen, do not spray. These insecticides will not only kill aphids, but also any predators or parasites that are present.

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