HPIPM:Seedcorn Maggot FC
Author: Frank B. Peairs[1]
Identification (and life cycle/seasonal history)
Seedcorn maggot, Delia platura (Meigen), adult flies resemble small, five millimeters long (1/5 inch), gray to brown house flies. They appear very early in the spring to lay eggs on moist soil near decaying vegetation. Large numbers may be seen flying over freshly worked soil. Seedcorn maggots are small, six millimeters (¼ inch), tapered, yellowish-white fly larvae. The maggots usually feed for about two or three weeks before changing into brown pupae. Adults emerge from the pupal stage in about a week to mate and begin a new cycle.
Plant Response and Damage
Damage occurs in the spring, usually during periods of prolonged cold weather after planting, when seeds fail to germinate rapidly. Maggots feed in the kernel, which may cause germination to fail or produce weak plants. Gaps and skips may occur in the emerging stand as a result of maggot damage.
Management Approaches
Scout for seedcorn maggot in areas where plants have failed to emerge. Dig two linear feet of row in five locations. Examine seed for maggots and feeding damage. Record number of plants, good ungerminated seeds, and hollowed out seeds. If stand is extensively damaged, replanting is the only available recourse. To prevent losses due to seedcorn maggot, corn seed should be treated at planting with a seed protectant. In general, seedcorn maggot problems are most likely to occur in situations where (1) high organic matter or decaying vegetation attracts egg laying female flies; and (2) cool, damp soil conditions delay seed germination and prolong the period vulnerable to maggot attack.
Chemical Control
Seedcorn maggot should not be a concern if a soil insecticide is used for control of corn rootworms. A corn seed protectant should be used if a soil insecticide is not used (see the rootworm chapter for details). Seed protectants are available with active ingredients including clothianidin (Poncho), imidacloprid (several products), permethrin (generic, several products), and thiamethoxam (Cruiser).
The information herein is supplied with the understanding that no discrimination is intended and that listing of commercial products, necessary to this guide, implies no endorsement by the authors or the Extension Services of Nebraska, Colorado, Wyoming or Montana. Criticism of products or equipment not listed is neither implied nor intended. Due to constantly changing labels, laws and regulations, the Extension Services can assume no liability for the suggested use of chemicals contained herein. Pesticides must be applied legally complying with all label directions and precautions on the pesticide container and any supplemental labeling and rules of state and federal pesticide regulatory agencies. State rules and regulations and special pesticide use allowances may vary from state to state: contact your State Department of Agriculture for the rules, regulations and allowances applicable in your state and locality.
