Therefore, control measures must be applied at planting time if economic damage is anticipated based upon past field history, farming practices, or cool weather conditions that result in delayed germination. After the seed is planted, the chance of insect damage is greater the longer germination is delayed. Wireworms infest corn and occasionally soybean fields and are found throughout Iowa. They are not considered to be serious pests in terms of annual acreage infested, but they occur often enough to cause severe stand losses in localized areas. Overall, the probability of any field suffering crop damage from wireworms is very low, except where the crop follows pasture or where problems have appeared during the past several years.
Wireworms damage corn in several ways.
Early-season injury is caused by larvae boring into the seed before or during germination and hollowing it out. Death and injury of seedling plants also can occur when larvae tunnel into the base of the plant below the soil line. Sometimes wireworms bore into the stalks of large plants and tunnel several inches above the soil surface. Seedcorn maggots are occasional pests of both germinating corn and soybean seeds, and cause reductions in yield because of stand loss. They are typically more of a problem in soybeans than corn and damage is more likely to occur during a cool, wet spring.