Carrot fly

Carrot fly (Psila rosae) is a significant pest that affects a variety of Umbelliferae crops, most notably carrots (Daucus carota), but also can affect parsley (Petroselinum crispum), celery (Apium graveolens), and parsnip (Pastinaca sativa). The larvae of the carrot fly cause damage by burrowing into the roots of these plants, leading to a condition known as "carrot rust," which can significantly reduce crop yields and marketability.

Life Cycle

The carrot fly has three generations per year in most regions. The first generation of flies emerges in late spring, laying eggs near the base of host plants. The eggs hatch into larvae, which then burrow into the soil to feed on the plant roots. After feeding and growing through several larval stages, these larvae pupate in the soil. The second generation of flies, emerging in mid-summer, can cause more severe damage as they lay eggs that develop into larvae during the peak growing season of their host plants. In some areas, a third generation may occur in late summer or early autumn.

Identification

Adult carrot flies are small, slender flies, about 5-8 mm in length, with a black body and a distinctive yellow-orange head. The larvae are creamy-white, legless maggots, approximately 1 cm in length when fully grown.

Damage

The larvae of the carrot fly are the primary cause of damage. They feed on the outer layers of the root, creating tunnels and leaving the root susceptible to secondary infections. Infested roots often exhibit reddish discoloration, and heavily infested plants may wilt or die. The damage not only reduces the aesthetic and commercial value of the crop but can also significantly impact yield.

Management

Management of carrot fly involves a combination of cultural, physical, and chemical strategies:

• Cultural Control: Crop rotation and the removal of infested plant material can help reduce the carrot fly population in the soil.
• Physical Control: Barriers such as fleece or fine mesh can prevent adult flies from laying eggs near the plants. Raised beds may also deter egg-laying.
• Chemical Control: Insecticides may be used, but their application is subject to regulatory approval and should be targeted to minimize impact on non-target species and the environment.
• Biological Control: Natural enemies of the carrot fly, such as certain nematodes and predatory beetles, can be introduced to help control larval populations.

Prevention

Preventative measures include sowing carrot seeds thinly to avoid thinning seedlings, which can attract adult flies, and planting resistant carrot varieties when available. Crop covers can be effective if applied before the first generation of flies emerges and left in place until the risk of infestation has passed.