Wireworms have chewing mouth parts and feed entirely underground. The larvae live in the soil, feeding upon the roots, seeds, and tubers of many plants. Damage is most likely to occur on poorly drained soil and on land from grass sod, because wireworms also feed on the roots of most cultivated and wild grasses.
Wireworms are especially destructive to corn, but all the small grains are also attacked.
Crops that are attacked by wireworms often fail to germinate because the insects eat the germ of the seed, leaving only the hollowed-out seed coat. In infested fields, a crop may not come up well or it may start well and later become thin and sparse because the larvae continue to bore into the underground parts of the stem causing the plant to wither and die. Later in the season, the wireworms continue to feed upon the small roots of many plants. Wireworm injury is most severe to crops planted on sodground or in a second-year sod, usually because the wireworms coming from sod fields have extended life histories. Wireworms lay in a straight line, while millipedes characteristically curl into a loose spiral position.