See fact sheet for Seedcorn Maggot
Several species (including seed corn and cabbage maggots). Yellowish white, legless; 1/4 to 1/3 inch long when full grown. Head end of maggot is tapered, rear end is blunt.
Cabbage, beet, beans, peas, mustard, radish, cauliflower, broccoli, brussels sprouts and turnip.
Destructive in seedbeds and on young transplants. Bore into sprouting seeds and prevent development of plants. Tunnel roots and stems, causing rot; plants wilt and die. Particularly destructive to early season plantings.
Seed corn maggot, throughout United States; cabbage maggot, in northern part of country.
Root maggots overwinter in soil as larvae. In spring larvae move near the soil surface where they pupate. In late spring adult flies can be observed in mating groups close to borders of fields, telephone poles, or tree trunks. Females deposit eggs in soil crevices near the base of plants. Larvae hatch and feed on roots.
Plow under crop debris immediatley after harvest to prevent use of plant remnants as overwintering sites. Root maggots prefer to lay their eggs in moist, organically rich soil, so avoid overfertilization with manure. Plow under weeds at least 2 weeks before planting garden. Planting transplants or pregerminated seed will help avoid damage by the seed corn maggot; however, even transplants of cruciferous crops have to be protected from cabbage maggots. Root maggot infestations can be prevented by covering the seedbed with a cheesecloth or screen covering placed immediately after seeds are sown. Covering should extend at least 6 inches on either side of the seed row. A square of tar paper (3 to 4 inches wide), or other sturdy material, placed at the base of each transplant will prevent adult cabbage maggots from laying eggs around stems. Cones made of window screen and placed over individual transplants will also prevent attack by cabbage maggots and have the advantage of being usable in subsequent years.
Dust plants with diatomaceous earth. Rove beetles are predaceous on root maggots.
Treat with a registered insecticide.
For broccoli and cauliflower: Apply a registered insecticide to entire seedbed before planting or transplanting and mix into the soil to a depth of 3 to 4 inches.
For cabbage: Apply a registered insecticide broadcast and work into the soil immediately before seeding the seedbed or transplanting.
For radishes: Apply a registered insecticide in seed furrow at planting.
For onions: Apply a registered insecticide in the seed furrow at planting.
Notice: Because pesticide labels can change rapidly, you should read the label directions carefully before buying and using any pesticides. Regardless of the information provided here, you should always follow the latest product label when using any pesticide. If you have any doubt, please contact your local Extension agent or pesticide dealer for the latest information on pesticide label changes.
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Prepared by Alexandra Spring and Eric Day (Modified from a publication by the USDA)