Delia platura, the corn seed maggot, is a native of Europe but was introduced to North America in 1865, where it has spread rapidly and is now commonly found infecting fields in throughout the United States, including Hawaii, and southern Canada. In its larval (maggot) phase, this insect burrows in the soil in fields feeding on recently germinated seeds. It is a serious pest of corn and bean seeds, and also attacks other species such as soybean, cabbage, cucumber, greenbeans, turnips, lettuce, onion, seed potatoes and cruciferous plants. Seedlings grazed on by the corn seed maggot grow up stunted and unhealthy with deformed or dead leaves. Affected beans often do not grow their primary leaves and produce less fruit; a heavy infestation may require a crop to be replanted. Larvae also cause openings in seedlings that are susceptible to secondary infection.
Delia platura can have up to five generations in a year. The maggot phase lasts up to 16 days; larvae are usually found, found around seeds in clusters of about 100.
Delia platura overwinters as a pupae, and hatches into a grey fly, similar to a housefly, the spring. Adult flies lay about 270 eggs in the soil near plant stems, and can be seen flying and hovering around fields as they feed on flower nectar. The most effective control method is to chemically treat seeds before planting. Removing flowers from areas around where crops are planted can also inhibit corn seed maggots, however this has the disadvantage of simultaneously reducing food sources for beneficial insects. Another effective non-chemical control method is to strategically manage plant timing to maximize germination rate, and ensure that soils that are not overly wet or contain much decaying organic matter, which are strong cues for adult oviposition. The maggot, because it is underground, is not susceptible to much predation and has few natural enemies.
(
Martin Kessing and Mau 1991;
Hadi et al. 2011)
