How to Manage Pests

UC Pest Management Guidelines

Dry Beans

Seedcorn Maggot

Scientific name: Delia platura

(Reviewed 8/07, updated 12/08)

In this Guideline:


The seedcorn maggot adult is a slender, light gray fly, about 0.20 inch (5 mm) long; it is less robust appearing than the housefly. The whitish eggs are slightly curved with their posterior bluntly rounded. Slightly raised ridges run the length and width of the eggs forming tiny rectangles twice as long as wide. Larvae range from 0.20 to 0.25 inch (5 to 6 mm) in length, are white to whitish yellow, cylindrical, and taper anteriorly. Pupae are small brown capsules. The seedcorn maggot is abundant during or following a wet cycle, which is primarily in spring, and is most common in fields containing a high amount of residue from a previous crop or where manure has been spread.


Seedcorn maggots burrow into bean seeds and prevent germination. Slow emergence and poor stand establishment are signs of seedcorn maggot activity. Where slow, spotty emergence is observed, seed should be dug up and inspected for maggot feeding. Soil and weather conditions such as cool soil temperature and periods of excessive moisture favoring slow seed germination and seedling emergence increase susceptibility to seedcorn maggot infestation.


Cultural Control
To reduce attractiveness of the field to egg-laying adults, disc or plow early in the season incorporating residues from a previous crop and destroying weed growth. Plant under ideal soil and weather conditions to assure rapid seed germination and minimize the seedcorn maggot problem.

Organically Acceptable Methods
Cultural control is acceptable in an organically certified crop.

Treatment Decisions
Begin inspecting plants for seedcorn maggot damage along with other pests and their damage when the crop emerges. Because a preventive seed treatment is the best method of control, note any signs of an infestation so that treated seed can be used in the future. Check with your local farm advisor about current registrations.


[UC Peer Reviewed]

UC IPM Pest Management Guidelines: Dry Beans
UC ANR Publication 3446

Insects and Mites

L. D. Godfrey, Entomology, UC Davis
R. F. Long, UC Cooperative Extension, Yolo County

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