Soybean aphids are approximately the size of a pinhead and are difficult to distinguish from beneficial aphids unless they are observed through a microscope.

The soybean aphid has a black tailpipe called cornicles on the tip of their abdomen. These tiny plant-feeding insects reside on the leaves of young soybean plants causing yellowing and malformation of the foliage. As the plant matures, the aphids spread to the stems and other parts of the plant, causing the plant to stop growing normally.

Aphids damage plants by inserting their slender beak like feeding apparatus into the plants' tissue to feed on the sap. Besides the direct damage caused by aphids, they also transmit viruses that cause the leaves to a mosaic appearance, reduced number of pods, discolored seeds and leaf distortion. Aside from damaging soybean plants, aphids also have a taste for other crops like potatoes and snap beans, and have been associated with transmitting viruses to those plants.

There are more than 8,000 species of aphids with about 800 in the Midwestern U.S. While aphids are widely known as pests, there are some beneficial aphids that are important to the life cycles of other plants and animals.