Root maggots are the larval stage of small flies, such as the cabbage root fly. These garden pests feed on the roots of various plants, causing damage. Root maggots feed on the roots of annual crops, like cabbages (Brassica oleracea), onions (Allium cepa) and carrots (Daucus carota). Other susceptible plants include turnips (Brassica rapa rapa), radishes (Raphanus sativus) and other members of the cabbage family. Check for symptoms of root maggots to protect your plants.
Because root maggots live beneath the soil, it is important to regularly check for eggs on plant stems. The female fly lays her eggs along the stems of susceptible plants or in cracks in the soil near the plants. Look for elongated white eggs, approximately 1/8 inch long, along the stems of plants. These eggs will be in orderly rows at soil level. When the female fly lays eggs beneath the soil, she leaves a small mound of dirt behind, near the plant stem. Gently move any mounds with a stick to search for eggs. Root maggot eggs are most prominent during wet weather and near young seedlings and transplants. If you find an average of one egg per plant stem, your plants may suffer significant damage.
Loss of Vigor
General symptoms of root maggots feeding on your plants include lack of vigor, poor growth and wilting despite proper care. Under heavy root maggot feeding, younger plants show the most loss of vigor, and may die. Older plants can withstand some root maggot feeding, although a heavy infestation poses a problem for any plant.
Signs Below the Soil
Lifting your plants from the soil and checking the root systems may be the only way to confirm root maggots. Gently move the soil aside to expose the plant's root system. Check the roots for legless, headless wormlike creatures, approximately 1/2 inch long. Root maggots are usually white to yellow.
Inedible Root Vegetables
While root maggots are the most damaging to young plants and seedlings, they ruin certain vegetables. These include root vegetables and members of the cabbage family. Root maggots tunnel into and eat their way through these vegetables, rendering the crop inedible. If you notice small holes in your vegetable plants, along with other signs or symptoms, root maggots are likely the culprit.
The best way to control root maggots is to prevent the female flies from laying their eggs in your garden soil. Protect members of the cabbage family with a brassica collar. Fitting around the stem of the plant, this collar prevents the female fly from laying eggs in the soil next to the stem. If the fly does lay eggs on the collar, they dry up and die. Insect netting or mesh can also block female flies from depositing eggs around plants. It is important to practice crop rotation. At the end of each season, till the soil thoroughly to destroy any eggs or pupae. Rotating your crops each season also prevents root maggots from overwintering in the soil. Women who are pregnant or nursing should always were gloves when working in garden soil to protect against soil-borne pathogens.