Each maggot feeds for three to four weeks, and the roots often become riddled with their tunnels. When the maggots are abundant, underground parts of the plants soon become honeycombed and rot. Over 125 maggots have been taken from the roots of a single plant. The cabbage maggot can be controlled by both cultural and chemical means. Any cultural practice that will reduce the decaying organic matter content of soil will reduce the chances of an infestation becoming established.
Any plant material left in the garden can attract flies.
If possible, till the soil 4 to 6 weeks before planting. This allows sufficient time for rotting of vegetation and may reduce the need for an insecticide treatment. Postemergence herbicides also contribute to cabbage maggot problems. Weedy fields where postemergence herbicide treatments are used often become infested with maggots as dead weeds decompose. Inspect these fields daily for flies and maggots a couple of weeks after herbicide use.