Seedcorn Maggots Damaging Early-Planted Soybean

Multiple samples of seedcorn maggot damaged soybean seedlings have been submitted to the Purdue Plant and Pest Diagnostic Lab. These damaged seedlings survived the recent snow and freezing temperatures, but not this early season soil pest! Remember that the adult female flies are attracted by rotting organic matter, this gives some clue about where infestations will be severe. Seeds planted into high crop residue, weedy growth, and/or where animal manure was applied are most often subject to attack by this pest.

Seedcorn maggot and damage to below ground cotyledons. (Photo Credit: John Obermeyer)

Seedcorn maggot and damage to below ground cotyledons. (Photo Credit: John Obermeyer)

Seedcorn maggots are small, yellowish-white maggots up to 1/4 inch long. They are the larval stage of a fly, very similar to a housefly in appearance.  Soils planted too wet often have open seed slots, attracting flies to climb down into the furrow and deposit eggs in decaying weeds next to the seed. Soybean and other crops are not the main target of this pest, but they will feed on them if they’re available. When the eggs hatch, they burrow into seeds or underground portion of plants and feed. The damage is usually first observed as skips in the row where plants do not emerge, or if they emerge, die back. Seedling blights are usually suspected first by those inspecting the poor stands, but digging around in those blank spots can confirm presence of maggots.

Emerged soybean seedling showing remains of seedcorn maggot damage that occurred below ground. (Photo Credit: John Obermeyer)

Emerged soybean seedling showing remains of seedcorn maggot damage that occurred below ground. (Photo Credit: John Obermeyer)

Seed applied insecticides will offer some protection of the seed. However, as the seed germinates, below ground portions of the plant, e.g., hypocotyl, are more vulnerable. Slow growing plants are more vulnerable as the seedlings are slow to emerge and subject to continual attack by maggots. Cooler soils exacerbate this situation. Should replanting be necessary, seed-applied insecticide is probably not necessary, as the seedcorn maggot will probably have already pupated (light brown, oval cases) and soon to emerge as an adult fly, meaning the damage is done and risk of further infestations is extremely low.

Finding pupa while digging for missing seedlings indicates that the damage has been done. (Photo Credit: John Obermeyer)

Finding pupa while digging for missing seedlings indicates that the damage has been done. (Photo Credit: John Obermeyer)

Share This Article
It is the policy of the Purdue University that all persons have equal opportunity and access to its educational programs, services, activities, and facilities without regard to race, religion, color, sex, age, national origin or ancestry, marital status, parental status, sexual orientation, disability or status as a veteran. Purdue is an Affirmative Action Institution. This material may be available in alternative formats. 1-888-EXT-INFO Disclaimer: Reference to products in this publication is not intended to be an endorsement to the exclusion of others which may have similar uses. Any person using products listed in this publication assumes full responsibility for their use in accordance with current directions of the manufacturer.
Pest&Crop newsletter - Department of Entomology Purdue University 901 W. State St. West Lafayette, IN 47907

© 2021 Purdue University | An equal access/equal opportunity university | Copyright Complaints | Maintained by Pest&Crop newsletter

If you have trouble accessing this page because of a disability, please contact Pest&Crop newsletter at luck@purdue.edu.