The whorl stage is the most vulnerable to aphid feeding. Infestations are sometimes not detected until tassels emerge from whorls and reveal black masses of aphids. Damage can be recognized by yellowing and shriveling of leaves. Often infestations resemble symptoms of plant disease. Aphid feeding functions as a nutrient sink, robbing nutrients from the reproductive portion of the plant.
Aphids also kill developing tassels and top leaves through their feeding.
The secretion of honeydew also may affect yield. Honeydew is an excellent substrate for sooty mold, which reduces photosynthesis. The sticky nature of honeydew may also reduce pollination if anthers and tassels are coated with high aphid densities. Stunted ears and poor kernel fill may result from the interference of pollination. Furthermore, honeydew also attracts other insects, including corn earworm and several beneficial insects.