Cabbage maggots overwinter as brown pupae in the soil and emerge as adults in the spring
Adults lay eggs on lower stems of host plants or in soil cracks
After 4-10 days, depending on temperatures, eggs hatch into larvae (maggots)
Larvae move down into the soil to feed on roots for around 3 weeks. This is the life phase that is destructive to plants
Larvae pupate underground, remaining as pupae for at least two weeks
Multiple overlapping generations occur each summer. Degree-day models for cabbage maggot can help identify when the first generation emerges, after which cabbage maggot pressure can be expected for the rest of the season.
Vulnerabilities and Preferences
Opportunities to disrupt the life cycle include the adults finding hosts to lay eggs and the larvae moving to plant roots to feed. There is not a known way to target the pupae phase of the life cycle
Managing residual plants and culled roots after harvest can prevent larvae from pupating and overwintering. Burying roots prevents larvae being able to reach them.
Adults typically fly within a couple feet of the ground, some success has been seen with using barriers between fields such as fences or hedgerows to make it more difficult for adult flies to move between fields.
We are conducting research on what cues adult flies to lay eggs on a plant, and whether particular varieties may be less attractive to flies. Leaf color and production of particular volatile compounds seem to be the cues adult flies use to find suitable host plants.
We are also investigating baited traps to attract adults and capture them on a sticky surface.
We are experimenting with spraying a barrier made of wood fibers over the soil after planting that deters adult flies from laying eggs. This is effective in laboratory trials, but requires work to be cost-effective at field scale.
