Insect Note #31 (Revised)
Prepared by:
Kenneth A. Sorensen, Extension Entomologist
Dated 2/94
Placed on the Web 4/95 by the Department of Entomology, NCSU
Revised: 03/05
The seedcorn maggot is an insect pest of beans, peas, cucumbers,
melons, corn, potatoes and other vegetables in North Carolina.
This maggot occurs throughout the United States, Canada, South
America, Europe, Asia, and South Africa.
Description of Injury
Food preferences appear to be sprouting and seedlings or decaying
parts of plants. Damage results in poor stands by direct feeding
or by association with a disease such as black leg on Irish
potatoes. The most severe damage usually occurs to spring crops in
high organic, cool, wet soils in which seed is planted too deep.
Life History
The winter is passed in the soil as a maggot inside a dark-brown
capsule. Small (about 1/5 inch long), grayish-brown flies emerge
in March and April. Adult flies are most active during midday.
They are inactive at night, during strong wind and rain and when
temperatures are below 50 degrees F or above 80 degrees F. Adults are most
abundant in freshly cultivated areas where eggs are laid near or on
sources of larval food. Favorite places for laying eggs are near
or on sprouting or decaying beans, peas, and/or in the vicinity of
such organic fertilizer materials as fish meal and cottonseed meal.
Yellowish-white maggots emerge and burrow into the soil and develop
on germinating seed. Full-grown larvae are about 1/4 inch long,
sharply pointed at the head end, legless, with a tough outer
covering. They change to the pupal stage inside a brown puparium
in the soil. As the entire life cycle may be completed in 3 weeks,
there are many generations per year.
Control
Adult flies are often detected in the spring clinging to
vegetation. They are susceptible to fungus disease (entomophthora)
during warm, moist weather. However, this disease is usually not
effective in reducing the initial flights and egg laying.
Weather conditions are important factors in the development,
activity and abundance of the seedcorn maggot. Development is
retarded greatly at average temperatures below 45 degrees F or above 75 degrees F.
An abundance of organic matter and moisture is conducive to larval
survival.
Avoid early planting in fields having cold, wet, high organic
soils. Shallow placement of seed in well-prepared soil favors
rapid germination, which evades injury due to maggots.
The use of seed treated with an insecticide is the easiest solution in the prevention of seedcorn
maggot injury. Most commercial seed is treated with pyrethrum,
which gives only marginal control.
The use of brand names and any mention or listing of commercial products or
services in this publication does not imply endorsements by the North Carolina
Cooperative Extension Service nor discrimination against similar products or
services not mentioned. All pesticide recommendations provided in this
publication apply to pest control in North Carolina. Individuals who use
chemicals are responsible for ensuring that the intended use complies with
current regulations and conforms to the product label. Be sure to obtain
information about product usage in your locale and examine a current product
label before applying any chemical. The information presented on pest
biology is based on conditions in North Carolina and may not be applicable
to your locale. For further information, we recommend that you contact the
Cooperative Extension Service office in your county.