The white, legless maggots feed or burrow into the roots and stems of the plant. They are blunt at the rear and pointed toward the head. The brown pupal cases are hard and egg-shaped. They over winter in the soil as pupae, when the soils warms in the spring, adults emerge, mate, then search for suitable host plants for egg laying. These maggots may eat small roots or tunnel into larger roots or stems.
Infested plants become riddled with winding tunnels.
Damaged plants may look wilted, gray-blue or purplish, stunted, or wilt during the heat of the day. Crops planted early when the weather is cool and wet for long periods of time are potentially at greater risk to damaging infestations of cabbage maggots. Control Successful control of cabbage pests, particularly the leaf feeding caterpillars, depends on proper pest identification, timing of applications and insecticide coverage. Most of the eggs of the foliage feeding caterpillars are laid on the undersurfaces of the leaves and the larvae, until mature, tend to feed on the underside of the foliage or in the bud. Thus, obtaining adequate coverage of the plants with an insecticide is difficult.