Submitted Photo Aphids will attack annual and perennial flowers, fruit plants and trees, vegetable plants as well as trees and shrubs. Photo from Christina DiFonzo, Michigan State University, Bugwood.org.

Aphids are a small, usually green, soft-bodied insect that suck plants juices from a variety of garden and landscape plants. They are typically found clustering on young shoots and leaves, although some species occur on flowers, twigs, branches and roots. Aphids will attack annual and perennial flowers, fruit plants and trees, vegetable plants as well as trees and shrubs.

Aphids seldom kill a plant, but when abundant they remove large quantities of plant juice, which reduces the vigor of the plant and can result in stunted plant growth. Leaves often become curled, puckered and yellowed due to aphid feeding. Some aphid species produce galls on stems and roots. Others transmit viruses or inject toxins into the plant when feeding.

Some aphid species take in more plant sap than they can use. The excess is excreted as a clear, sweet, sticky substance known as “honeydew.” Some tree-feeding aphids can produce such large amounts of honeydew that it often can be seen covering leaves, vehicles or other surfaces below the infested tree. Often found growing on the honeydew is a black, sooty mold (fungi) that not only disfigures the appearance of plants but may also restrict photosynthesis. Honeydew is attractive to ants, flies, wasps and bees, whose populations around infested plants can become a nuisance.

Control options can be quite simple. Aphids are not strong climbers, so physically removing them from especially trees will control most of them. This is best accomplished with a garden hose, higher water pressure, and a nozzle with a tight, strong stream pattern. Vigorously spraying the plant will wash the aphids off the plant. They are not strong climbers, so re-infestation will not usually occur unless the plants are very small or low growing.

Insecticidal soap and Neem oil are two organic compounds that can be sprayed on aphids to control them. There are a number of different chemical insecticides which will control aphids very well. Before using any insecticide for control be sure to read and then follow the label information and instructions.

Ken Eraas is the Ward County Extension horticulture assistant. You can reach him by calling 857-6444 or emailing kendell.eraas@ndsu.edu.