There are numerous species of the root maggot found In gardens in the United States. These pests feed on immature plants at the root, causing rot due to their feeding and tunneling.
The maggots destroy a wide variety of garden vegetables including cabbage, carrots, onions, turnips, and radishes.
Roots that are heavily infested by these maggots will have visible tunnels and rot with plants often showing signs of yellowing and wilting. In worst cases, the root maggot can destroy the plant by completely chewing through the roots.
The adult of the root maggot is a gray fly that is 1/5 of an inch long and is similar in features to the pesky housefly.
Adults emerge in late Spring from their pupal stage in the soil and begin the mating process.
Impregnated females can sense newly planted seedlings and will deposit anywhere from 50 to 200 eggs under the soil in the stem of the plant. The eggs hatch in a few days and the larvae travel further down into the soil to feed on roots and germinating seeds.
Root maggot larvae grow from ⅓ to ¼ inches in length during the feeding process and have a yellowish-white color with a pointed head.
After a couple of weeks of feeding, the maggots begin to pupae down in the soil or the roots of the plant until they emerge as an adult.
Because the females can sense the moisture on new seedlings for laying their eggs, controlling the pests can be done naturally by placing floating row covers over seedbeds as soon as they are sown.
Tilling the soil after harvesting can expose the maggots so that enemy predators can easily spot them.
Applying beneficial nematodes into the garden soil and around the base of the plants can help reduce a larvae infestation.