Carrot rust fly

About

A small fly whose larvae tunnel into carrots and their relatives. It is named for the rust-colored droppings in its tunnels.

Spotting it

Damage

Roots are scarred with rusty brown tunnels, and damage builds through the season.

How to find it early

Set yellow sticky traps at the edge of the carrot bed, and pull a test carrot to check for rusty tunnels.

When

Spring through fall.

Life cycle

In the Pacific Northwest there are three generations a year: flies emerge from early April to mid-June, a second generation in mid-July to September, and the last overwinters in the soil. Larvae feed on root hairs for about two weeks, then tunnel into the roots for about two more before pupating.

What to do, gentlest first

Start at the top. Sprays are a last step; always read and follow the product label.

1. Time the sowing Prevent

   In the Pacific Northwest, sow after mid-May (late May to early June is best) to miss the first generation, and harvest early or in blocks.

2. Rotate and clean up Prevent

   Do not replant carrot-family crops where they were infested, grow resistant carrots such as 'Flyaway', remove infested roots, and till in fall or spring to expose pupae.

3. Yellow sticky traps By hand

   Use traps at the bed edge to tell when flies are active.

4. Row cover sealed with soil Barrier

   Cover beds right after sowing, bury all the edges in soil, and leave the cover on until harvest.

5. Few home options Conventional spray

   Oregon State says available pesticides are unlikely to control large populations, and organic options such as spinosad, neem and pyrethrum remain largely untested in the Pacific Northwest, so rely on timing and covers.

Plants it goes after

Caraway, Carrot, Cilantro (coriander), Dill, Parsley

Pressure by region

Washington State University says it thrives north of the 40th parallel, especially in the Northeast and on the West Coast. Other regions are rated low for lack of a source, so those ratings are estimates.

Ratings come from extension sources where available; some are estimates, as noted above.