How to Manage Pests

Cabbage maggot—Delia radicum

Cabbage maggot larvae are small, legless, and white, 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 that 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, these maggots are active throughout the year and have several generations.

Damage

Maggots tunnel through root systems of all cole crops. Tunnels provide entryways for pathogens. Youngest plants are most susceptible; healthy plants attacked after they are well established can usually tolerate moderate infestations.

Solutions

Prevention is the best management strategy. Avoid overfertilization with manure; maggots prefer to lay eggs in rich soil. Disc weeds at least two weeks before planting. Plant transplants or pregerminated seeds. Cover seedbeds with protective cloth or cover individual plants. Remove infested plants. Once plants are infested, maggots cannot be reliably controlled with pesticides.

Cabbage maggot larvae

Damage to root of seedling