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Seed Corn Maggot

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This page was adapted from the article, "High Risk for Seed Corn Maggot" which appeared in Crop & Pest Report on May 26, 2022.

Cool wet springs favor the infestation of seed corn maggots in many field crops including sugar beets, peas, lentils, dry beans, soybeans and corn. Besides cool wet weather during early crop stages, soils that have high organic matter or manure spread on it will increase risks for seed corn maggot infestations. This spring has been so wet and cool that conditions have been ideal for maggot infestation.

A hairy gray fly on the end of a pin
Photo Credit:
Pest and Diseases Image Library, Bugwood.org
Seed corn maggot adult.

Seed corn maggots overwinter in the soil as pupae. Adult flies emerge from the puparium in spring when soil temperatures reach 50oF. They deposit eggs in soil where there is abundant organic matter and decaying green crop residue, or on the seed or seedling. The egg hatches in 2-4 days and a seed corn maggot (larva) emerges from the egg.

A close up of a small, off-white maggot on a yellow-white plant stem
Photo Credit:
W. Cranshaw, Colorado State University, Bugwood.org
Seed corn maggot larva

Maggots fed on the seed, weakening seedlings and decreasing plant stand counts. The yellowish-white, headless and legless maggot, about <¼ inch, can often be observed burrowing into the seed or emerging stems. Larvae pupate in the soil and an adult fly will emerge in 12 -14 days. There are multiple generations per year (4-5). 

Three white maggots at the bottom of a yellowing plant stem. The plant leaves are slightly withered.
Seed corn maggot larvae

The decision to manage seed corn maggots must be made before purchasing seed or planting. Insecticide seed treatments and insecticides applied at planting will control seed corn maggots. When conditions are wet and cool, or if planting into high green cover crop / crop residue conditions, seed treatments will provide the best defense against crop injury. Delayed planting also can mitigate seed corn maggot injury by increasing the rate of seed germination due to warmer soil temperatures. Consult the E-1143 North Dakota Field Crop Insect Management Guide 2022 for insecticide treatment registered by crop.