Root maggots prefer to lay their eggs in moist, organically rich soil, so avoid overfertilization with manure. Plow under weeds at least 2 weeks before planting garden. Root maggot infestations can be prevented by covering the seedbed with a cheesecloth or screen covering placed immediately after seeds are sown. Covering should extend at least 6 inches on either side of the seed row. Cones made of window screen and placed over individual transplants will also prevent attack by cabbage maggots and have the advantage of being usable in subsequent years.
Dust plants with diatomaceous earth.
Rove beetles are predaceous on root maggots. Treat with a registered insecticide. Because pesticide labels can change rapidly, you should read the label directions carefully before buying and using any pesticides. Regardless of the information provided here, you should always follow the latest product label when using any pesticide. If you have any doubt, please contact your local Extension agent or pesticide dealer for the latest information on pesticide label changes.