James R. Baker, Extension Entomologist

Aphids are sometimes pests of ornamental trees, shrubs and flowers. They feed by inserting microscopically thin mouthparts into the plant phloem and sucking out sap that is rich in sugars. As they feed, aphids also inject saliva. This saliva causes some plants to develop curled, hardened or distorted growth. Overall plant vigor may suffer. Aphids are slow, fragile, insects that vary from 1/16 to 1/4 inch long. They can be black, brown, yellow, red, gray or green. Most of the aphids are without a waxy covering, although the bodies of some of the woolly aphids are covered with white, waxy threads.

Some aphids have white spots or are completely covered with a white waxy powder. The legs and antennae are usually long and fragile. Aphids may be wingless or have functional wings. The offspring are smaller than the adults and are always wingless.

BIOLOGY

While feeding, aphids inject saliva into the plant. The saliva of some aphids causes curled or distorted growth. Some aphids transmit plant viruses as well. Aphids excrete a sweet, sticky liquid called honeydew. When aphid numbers are large, honeydew often completely coats leaves and other object below, giving infested plants a sticky or varnished appearance. Honeydew attracts ants, flies, wasps and other insects. Unsightly fungi called sooty molds often develop in honeydew, further disfiguring plants.

Many species of aphids in North Carolina overwinter in the egg stage, however, during the growing season, all aphids give birth to living young. The young aphids mature in about 10 days. Most aphids species have several generations per year. Both winged and wingless aphids are born during the growing season. Winged forms migrate to start new colonies, usually on the same type of plant. Some aphids, however, can move to an entirely different species of plant. Although most aphids attack the tender stems and leaves, a few feed on roots of certain plants. For example, the woolly apple aphids feeds on the leaves of elm trees and the roots and stems of crabapples, apples and pyracantha.

CONTROL

Natural enemies of aphids include ladybird beetles and their larvae, green lacewings and their larvae (aphid lions) which sometimes disguise themselves(2) with debris, hover fly maggots, parasitic wasps and entomophagous fungi. Sometimes these parasites and predators are not able to keep aphids under control, so chemical control may be needed. The following sprays may be used to control aphids. Sometimes two applications of an insecticide at 7- to 10-day intervals are needed. Repeat application when needed as aphids reappear. Don't ignore the practice of merely wiping off or gently washing off small concentrations of aphids in the garden.  See a note from Texas about using high pressure water spray.

* Suitable for homeowner use.

Visit a nice Wisconsin Aphid Page: http://www.hort.wisc.edu/mastergardener/Features/insects/aphids/aphids.htm

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Published by North Carolina Cooperative Extension Service

Distributed in furtherance of the Acts of Congress of May 8 and June 30, 1914. Employment and program opportunities are offered to all people regardless of race, color, national origin, sex, age, or disability. North Carolina State University at Raleigh, North Carolina A&T State University, U.S. Department of Agriculture, and local governments cooperating.

Prepared by: James R. Baker, Extension Entomologist
ENT/ort-38 February 1997 (Revised)

Web page last reviewed January, 2008 by the webperson.