Radish root maggot Delia planipalpis
IDENTIFICATION – The radish root maggot can be a particularly rude pest in the vegetable garden. These pale larvae tunnel through the root flesh of many root crops, leaving unsightly, slimy brown trails. Members of the mustard family, including radish and turnip, are most often affected. This damage isn’t visible until the crop is harvested and prepared. Wilting of the foliage may be seen before harvest.
LIFE CYCLE – The radish root maggot is the larval stage of a tiny fly. The adult female fly lays her eggs on the leaves of host plants. The eggs hatch and the larvae then drop to the ground and begin tunneling into the root tissue. They survive winter as pupae that look somewhat like seeds in the soil.
CONTROL – Once your radish or turnip crop has been damaged, there is nothing you can do to save it. At this point, pull all the plants and throw them away. Don’t compost them because the maggots will complete their life cycle in your compost pile and be ready to infest the next crop. The best control is prevention. In the spring after you sow seeds for radish, tent the planting with floating row cover, available at your garden center. Tenting will prevent the adult flies from laying eggs on the leaves. Be sure to cover the entire row and seal the edges with soil or rocks. Keep the radishes covered during the entire growing season. Rotating crops with non-mustard crops like tomatoes, beans, peas or even herbs also helps discourage this pest, as well as many others.