Organically Controlling Carrot Rust Fly

While larvae of any type will leave trails in soil as they burrow, the carrot rust fly larvae will leave a rusty-colored tunnel when they burrow into your caraway, carrot, celery and coriander plant roots, as well as dill, fennel, parsley and parsnip roots.

Organically Controlling Carrot Rust Fly: Know What It Looks Like

Carrot rust fly starts out as tiny yellow-white larvae and is only about a third of an inch long. Later, the adult fly will be slender and a shiny green color. This fly can produce several different generations per year, laying its eggs at the carrot and other plant crowns during the late spring.

Carrot Rust Fly: The Signs You Have It

Leaves on your dill, fennel, parsnip, and parsley plants-or your carrot, celery, caraway and coriander plants-will wilt and turn yellow due to carrot rust fly. Your carrots will have soft rot bacterial in them, and all the plants affected will have stunted growth.

Organically Controlling Carrot Rust Fly

Using row covers during all seasons will help organically control this insect, but rotating crops, and avoiding early planting will help too. It is best to plant your crops after the maggot peaks. Other organic remedies to use with carrot rust fly include the use of yellow sticky traps (at a 45 degree angle), sowing your seeds with used tea leaves, and spreading wood ashes (or pulverized wormwood) around the crown of the plant.

Do these things to repel the carrot rust fly from laying eggs. You can use rock phosphate around the plant crown too, as well, in order to prevent egg-laying, but do so experimentally.

Carrot Rust Fly: What About Allies For Organically Controlling Carrot Rust Flys?

Lettuce, rosemary and sage are allies that can aid you in protecting your plants from carrot rust fly damage. And so are black salsify (an oyster plant) as well as pennyroyal.

Source
"The Gardener's A-Z Guide to Growing Food Organically" by Tanya L.K. Denckla