Insect identification > Homoptera > Aphids > Corn root aphids

Corn root aphids

The corn root aphid (Anuraphis maidi-radicis Forbes). - This insect, though it can hardly be regarded as universally distributed throughout the United States, is both a serious pest of corn over a large area and, because of its remarkable relation with ants, an interesting species. It appears to occur throughout the Eastern United States as far west as South Dakota and Colorado and south to South Carolina, Louisiana and Texas, but its destructive work mainly covers the territory from New Jersey to South Carolina and west to the Mississippi River.

The eggs of this aphid hatch early in spring and from 10 to 22 generations are produced during the season. As cool fall weather appears, a generation of sexual individuals appears and these lay eggs which pass the winter. During this season these may be found in the ground in nests of several kinds of ants but most frequently in those of the cornfield ant Lasius niger americanus. They are oval, black and glistening, and are sometimes found in small piles in the nests of the ants.

In cold weather the ants carry the eggs down below the frost and on warm days bring them up to warmer levels. In spring, when various weeds, such as smartweed, begin. to the rest of the season. Winged migrants are produced after a generation or two and these individuals, spreading, are taken to corn roots by ants which may find them.

All summer and fall the ants care for the aphids, taking them from one plant to another and collecting from them the honeydew upon which the ants feed. In the fall when the eggs are laid, these are gathered by the ants and stored in their nests over winter.

Where the corn root aphid is abundant it becomes a serious corn pest, dwarfing the corn and turning the leaves yellow or reddish and sometimes destroying the plants, particularly when weather conditions are also unfavorable.