Insects: Seed Corn Maggot

Taxonomy:

Distribution:

• From Europe, it is now established and distributed throughout the United States and southern Canada.

Importance:

• They burrow into and feed on all types of seeds in the soil reducing crop stand.

Identification:

• Adults resemble small houseflies.


• They are gray to light brown and about 1/4-inch long.


• Larvae (maggots) are yellowish-white, legless and about 1/4-inch long.


• They are blunt at the posterior end and tapered sharply to the head.

Life Cycle:

• The larvae over winter inside a dark brown puparium in the soil that resembles a dark wheat seed.


• In April and May adults hover over freshly worked soil.


• Adults may be more readily attracted to fields with an abundance of decaying organic matter (i.e., newly plowed or destroyed small grain or heavy applications of manure).


• Adult females lay eggs in decaying organic matter.


• The life cycle (egg through adult) takes about three weeks.

• There are three to five generations each year.


• Later generations are of little economic importance.

Host Range:

• Extensive, but corn and soybeans are among the major crops attacked.

Injury & Damage:

• Maggots burrow into and feed on seeds.


• Damaged seed may germinate, but plants generally don't survive.


• Maggots also attack stems that are underground resulting in weakened seedlings that rarely survive.


• Reduced plant stands are evident about a week after the corn plants start emerging.


• Damage is more likely in cool, wet soils when the seeds are slow to germinate but the insects are actively feeding.

Management:

• Because this damage occurs below the soil surface, it may be difficult to determine the need for an insecticide.


• There are no rescue treatments for this insect, so insecticides need to be applied at planting if economic damage is anticipated.


• Seeds are at greatest risk for injury when the soil is high in organic matter.