Aphids

Susceptible Plants
Many plants, including trees, shrubs, perennials, annuals, and vegetables

Description & Symptoms
Aphids are small, soft-bodied, sucking insects that feed on plant sap. They can be brown, black, red, yellow, green, or other colors. Although they are usually smaller than 1/8 inch in length, they can be easily seen when they cluster in large numbers on plants. They frequently are found massed on young succulent growth, such as new shoots, buds, and leaves. Leaves and stems that are infested with aphids do not grow properly, often becoming yellowed, distorted, or curled.

Timing & Life Cycle
Aphids are a common garden pest and can appear at any time during the growing season. They reproduce many times a year, and populations can easily get very large. Most do not fly, but some have small transparent wings.

Damage
Heavy infestations of aphids can slowly weaken a plant and cause stunted and distorted growth. Some aphids excrete "honeydew," a sugar-laden substance that coats leaves and causes the growth of sooty mold, an unsightly but harmless black fungus. However, a large amount of sooty mold will interfere with a plant’s ability to photosynthesize and exchange oxygen.

Treatment & Solutions
Since most aphids are soft-bodied insects that do not fly, they can be knocked off a plant with a hard spray of water from a hose. Alternatively, stems that are covered with aphids can be pruned out. Aphids also can be controlled with insecticidal soap, which must be sprayed directly on the insects to be effective. As with all products, it is important to carefully follow directions on the package when applying insecticidal soap.

Please contact Plant Information Service at (847) 835-0972 or via e-mail at plantinfo@chicagobotanic.org for current recommendations on treating aphids.