How to Manage Pests

Seedcorn maggot—Delia platura

Seedcorn maggot larvae are small, legless, white maggots usually less than 0.33 inch when full grown; the head end is pointed and the rear is blunt. Adults are dark gray flies about half the size of the common housefly.

Life cycle

The life cycles of maggots on vegetable crops are similar. Adult maggots are dark gray flies that resemble the common housefly. Females lay small white eggs in plant stems right at the soil line or in cracks in the soil near plant stems. Eggs hatch in a few days and the maggots burrow through to roots or germinating seeds. The maggots are small, white, and legless -- usually less than 0.33 inch when full grown. After feeding for one to several weeks, maggots pupate in roots or surrounding soil. Pupae are brown and egg shaped. In most California growing areas, maggots are active throughout the year and have several generations.

Damage

Maggots kill germinating seeds and very small seedlings. Once the stand is established and seedlings have developed a few leaves, maggots are unlikely to cause economic damage.

Solutions

Cool, wet weather promotes seedcorn maggot infestations. Prevention is the best management strategy. Avoid overfertilization with manure; maggots prefer to lay eggs in rich soil. Disc weeds at least 2 weeks before planting. Plant transplants or pregerminated seeds. Plant seeds under conditions to promote rapid germination and establishment. Cover seedbeds with protective cloth or cover individual plants to prevent adults from laying eggs near plants.

Adult seedcorn maggot

Larva, prepupa, and pupae of seedcorn maggot

Damage to germinating seedlings