A decision to treat is made even more difficult because there are no rescue treatments for these insects. After the seed is planted, the chance of insect damage is greater the longer germination is delayed. They are not serious pests in terms of annual acreage infested, but they occur often enough to cause severe stand loss in some fields. The probability of crop damage from wireworms is low, except where corn follows a grassy situation such as pasture or CRP ground, or where problems have appeared during the past several years. Problems can persist in a corn field because wireworms live for two to six years.
Wireworms damage corn in several ways.
Early-season damage occurs when larvae bore into the seed before or during germination and hollow it out. Death of seedling plants also can occur when wireworms tunnel into the seedling stalk. Sometimes wireworms bore into the stalks of larger plants and tunnel several inches above the soil surface. Seedcorn maggots are occasional pests of both germinating corn and soybean seed that cause reductions in yield because of stand loss. The greatest potential for injury to seeds is when animal manure is spread on the soil or when live, green plants are killed in the spring prior to planting.