Seedcorn Maggot
Hylemya platura (Meigan), Anthomyiidae, DIPTERA

DESCRIPTION

Adult - This gray, black-legged fly has scattered bristles on its body and is approximately 5 mm long.

Egg - Each white, elongate egg has a rough surface and is about 1 mm in length.

Larva - This 12-segmented, white to yellow maggot is 5 to 7 mm long when mature. It is legless and tough skinned with a sharply pointed head and a rounded tail.

Pupa - The last larval skin hardens to form a puparium (about 5 mm long) in which the pupa develops. The ivory puparium gradually turns reddish-brown as the pupa matures.

BIOLOGY

Distribution - The seedcorn maggot was not identified in North America until 1855 when it was discovered in New York. Common throughout the temperature zones of the world, it has now been identified in all arable portions of North America from southern Canada into Mexico. Although widespread in the United States, it has not been found at altitudes in excess of 1.4 km (4500 ft) above sea level.

Host Plants - Although it feeds primarily on decaying organic matter, the seedcorn maggot infests the germinating seeds and roots of over 47 living plants. Beans, soybeans, and peas are the most seriously damaged hosts. To a lesser extent, crucifers, cereals, potato seed pieces, cucurbits, corn, tobacco, onions, pepper, buckwheat, and alfalfa are also injured by this pest.

Damage - This insect is usually a problem during cold, wet seasons and in highly organic soils. Seedcorn maggots feed on the seed contents often leaving only empty shells and thereby causing seed death or poor germination. The seedlings which do emerge ar tall and spindly with few leaves. They rarely mature and, even then, maturity is late and seed quality poor. Occasionally seedcorn maggots tunnel in these seedling stems. Either type of feeding allows the entry of disease-causing organisms.

Life History - In North Carolina, all stages of the seedcorn maggot can be found throughout the winter. Further north, however, the insects overwinter in the soil as pupae. The adult flies emerge from puparia at night or early in the morning and push themselves up to the soil surface. For a variable length of time, adults feed on nectar and honeydew. At the end of this period, each fertilized female begins laying an average of 270 eggs, singly or in small clusters. Moist, freshly disturbed soil, fields with decaying seed or crop remnants, and/or organically fertilized soils are all attractive to ovipositing female flies.

Eggs hatch in 1 to 9 days depending on the temperature. The newly hatched larvae tunnel in seeds or other decaying vegetable matter. Maggots remain active at temperatures as low as 4.4 degrees C (40 degrees F). They develop through three larval stages. After feeding for 1 to 3 weeks, the larvae pupate as deep as 18 cm in the soil. Pupation may last 7 to 26 days or all winter.

CONTROL

For control of seedcorn maggots in field or vegetable crops, shallow planting in a well-prepared seedbed, sufficiently late so that quick seed germination is ensured, is one means of preventing injury. A field where manure is heavy or where a cover crop is turned under should be plowed early in the fall, if possible; it will be less attractive to the egg-laying flies the following spring. Prompt resetting or replanting of damaged crops will usually give a good stand.

Combination fungicide-insecticide seed treatments or soil-applied insecticides can be used to prevent seedcorn maggot damage. For further control information, consult the current North Carolina Agricultural Chemicals Manual.