Aphids on Vegetables

Injury

Aphid adults and nymphs pierce plants with their needlelike mouthparts and extract plant juices from the foliage of nearly all vegetable and fruit crops, usually from the undersides of leaves or at active growing points. Plants become weakened and lose vigor, leaves wilt and curl downward, as well as become distorted and discolored. Heavy damage will cause the leaves to desiccate and drop from the plant. Aphids secrete honeydew, a mixture of excess water and sugars, that sticks to the leaves and fruit, enabling black sooty mold to develop wherever the honeydew is deposited. These insects also may transmit various plant diseases, including cucumber and melon mosaic, potato leaf roll, beet mosaic, potato virus, zucchini yellow mosaic, numerous virus diseases of pepper, and lettuce mosaic.

Description

Aphids are small, 1/16" to 1/8" long soft-bodied, pear-shaped insects that may be pink, green, bluish-green, black, brown, tan, or yellow in color. Aphid adults may or may not be winged, and all adults have a pair of cornicles, often appearing as slender, tail-pipe-like appendages sticking up on the end of the abdomen.

Life History

In New Jersey, most species of aphids overwinter as eggs on a host plant or tree. In spring, aphids hatch from the eggs and begin giving birth to wingless females that remain on the overwintering plant for several generations, after which most of the aphids develop wings and migrate to new host plants to begin a colony of wingless females. These females can give birth to more wingless females, allowing aphid populations to build up rapidly. As fall approaches, winged males and females develop and fly to the winter host plant, where the females give birth to the true sexual females, which then mate with the winged males. These females deposit eggs on the overwintering host plant, completing the life cycle.

Aphid Management

1. Weeds (mustards, dock, etc.) near the garden should be destroyed to reduce the transmission of plant diseases to the cultivated crop. However, the number of hosts is very large, rendering this tactic unreliable.
2. Destroy or remove all diseased plants from the garden.
3. Ladybug beetles and lacewings, and the larvae of both, are common predators of aphids. Learn to recognize these and other beneficial insects. Companion plantings of dill, coriander, yarrow, and fennel are known to attract insects that prey on or parasitize aphids. For more information on this topic, see FS295, Beneficial Insects of the Home Garden.
4. Reflective mulches, such as silver or aluminum plastic mulches, can be used to delay colonization by winged aphids and thus reduce aphid feeding and transmission of plant diseases.
5. Over-fertilization with nitrogen often increases aphid populations.
6. Avoid overuse of insecticides as you may kill beneficial insects and actually cause aphid outbreaks. If a pesticide is used, apply before the population level is high and the leaves begin curling. Obtain thorough coverage of the foliage, especially on the undersides of the leaves. Read and follow all pesticide label directions, restrictions, and pre-cautionary statements before using any pesticide. Remember that insecticides may be harmful to bees foraging in the area. Pesticide applications late in the day or at night will avoid actively foraging bees. Days to harvest after last application varies depending on crop and pesticide—refer to the label for appropriate time intervals. For more information on insecticides recommended for use on aphids, see FS1123, Vegetable Insect Control Recommendations for Home Gardens.