Adult seed corn maggots are medium-sized flies that are very similar in appearance to the common house fly. Adult flies are present throughout the growing season and locate egg-laying sites by flying alternately close to the ground’s surface or searching the moist soil cracks on the soil surface. The adult female flies search for egg-laying sites close to decaying plant material or germinating seeds to provide a food source for the newly hatched larvae. Adult flies lay eggs in moist soil cracks near these potential food sources, and typical-looking fly larvae (maggots) hatch from the eggs within a few days. After hatching, larvae move through the soil searching for decaying plant matter or germinating seeds to feed on.
Large-seeded crops like soybeans are very susceptible to seed corn maggot attack, resulting in stand losses. Germinating soybean seeds are often killed or severely injured, thereby reducing plant populations within an area of the field or throughout the entire field. Losses typically range from 3,000 to 8,000 plants per acre. Fields in which animal or green manure crops have been used have a greater potential for seed corn maggot attack than fields not using these manures. However, non-manured fields are also at risk from seed corn maggot damage.
Seed corn maggot is easily and inexpensively controlled with the regular use of insecticide added to the planter box as a seed treatment or seed which has been pretreated with a seed corn maggot active insecticide.