How to identify and get rid of root maggots using time-tested, organic and natural methods.
Many species of root grubs are found in home gardens throughout North America. Particularly destructive to early-season plantings, they feed underground on succulent roots and attack a wide range of vegetable crops, including radishes, cabbage, carrots, turnips and onions. Heavily infected roots often become tunneled and rot. Affected plants lose vigor, may be stunted or yellow, and often wilt in the heat of the day. In some cases, the larvae can even chew through taproots, causing plant death.
Identification
Adults (1/5 inch long) are dark gray flies similar to the common housefly, only smaller in size. They lay eggs in the soil at the base of host plants and are very good at detecting newly planted beds. The grubs (1/3 to 1/4 inch long) are small, yellowish-white, legless larvae with conical or pointed heads and a blunt rear end.
Note: Entry and feeding by this pest creates entry points for diseases such as black rot.
Life cycle
Adults emerge in spring or early summer from pupal cocoons overwintering in the soil. They soon mate and the females begin laying 50–200 small white eggs in plant stems right at the soil line or in cracks in the soil near plant stems. The eggs hatch after a few days and the larvae burrow into the soil to feed on small roots, root hairs and germinating seeds. After feeding for 1-3 weeks, the larvae begin to pupate in plant roots or surrounding soil. There are several generations in a year.
How to control
- Female flies are attracted to the moisture released from newly planted seed rows to lay eggs. Cover seed beds with floating cover immediately after sowing seeds to prevent problems. Make sure the cover extends at least 6 inches on each side of the seed rows.
- Apply a small amount of diatomaceous earth around the stems of the seedlings to prevent the adults from laying eggs.
- Yellow sticky traps placed around vegetable crops will catch many adult flies before they can mate and lay eggs.
- Thick paper collars or other durable material can be placed around the base of the graft to prevent eggs from being laid around the stems.
- Applying beneficial nematodes into seed furrows or as a top dressing around plants can be effective in getting rid of larvae.
- Using pyrethrin impregnation is also an effective option, but should only be considered as a last resort.
- Rototyling under crop residues immediately after harvest to destroy wintering areas.
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