The tiny white maggots (larvae) of this pest leave crop roots riddled with dark tunnels. Carrot rust flies target carrots and related crops; parsnip, celery, celeriac, and parsley. The flies lay their eggs in the soil near these plants. When the eggs hatch, the maggots tunnel into the roots and crowns, remaining active for about one month. The longer mature crops remain in the soil, the more likely they are to be damaged. The carrot rust fly larvae?s tunneling activity leaves behind a rust-colored stain, which is what gives this pest its name. The tunneling damages the appearance of roots, reduces storage quality and invites disease.
Carrot rust flies spend the winter in the pupa stage, and there are two generations per year. This pest was introduced from Europe over 100 years ago, and has spread through most parts of the northern United States and Canada.
Prevention and Control
- Plant carrot varieties that have proven to be resistant to the carrot fly, such as Fly Away.
- In cold areas, plant carrot-family crops later in spring to avoid the first generation of adults. In mild climates, sow seeds in late winter or early fall.
- Cover vulnerable crops with garden fabric to prevent the adult carrot fly from laying its eggs. Leave cover in place until harvest.
- If plants are not covered, harvest earlier in fall to avoid damage from the second generation.
- In fall, minimize the opportunity for carrot fly pupa to overwinter by removing weeds from in and around the garden, especially carrot relatives such as Queen Anne?s lace.
