How To Fight Carrot Root Flies

by Matt Gibson

The carrot root fly is the main pest that attacks carrots—and one that gardeners need to be ready to go to battle with when harvesting carrots and other members of the umbelliferae (or apiaceae) family, which includes carrots as well as celery, dill, fennel, parsley, parsnip, and celeriac.

The eight-mm-long flies lay eggs in the soil near your carrot patch. Shortly afterward, tiny white maggots hatch and burrow into the plants’ root systems, eating as they go. First the leaves of the plant begin to turn red, then they wilt. The carrots themselves are still edible, but you will have to be okay with a bit of sharing with the larvae, as they will have no doubt already tunneled deep into the carrot and eaten their fair share.

Fortunately for gardeners with a fondness for carrots, the carrot root flies are not indestructible, and there are many preventive measures you can take to avoid having to share with or eat after the disgusting cream-colored maggot larvae you would otherwise have to endure. Mmmm, nope. No one, I mean absolutely no one, wants to eat after maggots—so read on, and read closely, so you will be prepared to keep carrot root flies away from your harvest and out of your garden.

Companion Planting: Pair With Alliums

Every species of plant has preferences when it comes to their neighbors. Some plants compete with one another over resources and are detrimental to the health of their neighbors, and some plants fit together perfectly and are beneficial when planted next to each other. Strong-scented alliums, such as garlic and chives, are perfect companion plants to carrots, and alliums will help drive away carrot flies as well as other garden pests.

Spread Carrot Crops in Several Locations

Many gardeners have found spreading their carrot plots out around the garden helps assure that at least some of the patches will go unharmed. Instead of growing one big carrot patch and bunching all of your carrot crop together in the same place, try placing a few carrot plots here and a few there throughout your garden beds. Carrots take longer than most vegetables to go bad, so having some extra laying around isn’t a catastrophe, and wasting food should be a nonissue.

Rotate Your Crops

Try not to plant the same crops in the same areas of your garden beds each planting season. After the larvae of the carrot root fly gets its fill, it winters in the soil surrounding the plants. If you plant your carrots in the same place you did last season, the flies will wake up, find familiar surroundings, and lay their eggs right in the middle of your carrots again. Rotating your crops each growing season is a simple fix to avoid this problem, and it’s also good for your fertile gardening soil to have more variety in plant needs from season to season.

Avoid Other Umbelliferae Family Crops

Parsnips, celery, and other members of the umbelliferae family also attract carrot root flies, so don’t plant these vegetables near your carrots, or you are asking for double trouble from carrot root flies. Be sure to do your research on companion plants well before planting and blueprint your garden bed layouts ahead of time to avoid bad combos that attract pests or grow competitively, draining each other’s resources.

Use Row Covers on Garden Beds

If possible, cover your vegetable beds with a fine mesh to keep flying insects from being able to lay eggs in the soil surrounding your veggies. Fleece is also a good cover for vegetable beds. Lay the fleece out gently over the top of your vegetable beds, and secure it firmly around the edges to keep out flies and other pests. While this method is not always feasible, most gardens can be covered with relative ease at low cost, and this preventive method can save you tons of work and stress in the long run, as well as a little bit less money spent on buying produce each year.

Nematodes: Beneficial Gardening Insects

Use some organic pest control weapons (such as sticky traps) or biological controls (such as treatments with carrot fly nematodes) to defend against carrot root flies. These nematode treatments are simple to apply and can ward off carrot root flies and many other pests with only one application per growing season. Simply mix the nematodes with water, and water the plants with the mixture during your normal watering time. The nematodes will disperse into the soil and go to war immediately with any threats to your veggies living there, killing every pest in sight and protecting your plants. SuperNemos is a well known and widely used brand of nematodes with good customer reviews.

Get a Late Start: Delay Planting Dates

Carrots grown later in the season, starting around June or later in the year, usually miss the first round of pests. Don’t just plant your carrots late and assume they will be fine, though—this early-bird strategy just allows them a good head start. You should still use other preventive methods to keep carrot root flies at bay, as a second cycle of eggs will hatch between July and September.

Above all, if you end up having to share your carrots with carrot root flies, don’t just give up and assume that the pests are destined to win. It’s all about timing and persistence. You can win the war, even if you lose a battle or two. Other than pest control, carrots do not require a great deal of care. Just keep the area where you grow your carrots free of weeds, watch out for overwatering, and you’ll be stockpiling perfect stores of these tasty root veggies in no time.

Want to learn more about how to fight carrot root flies?

Gardener’s World covers 10 Ways to Get Rid of Carrot Root Fly
Grow Veg explains How to Prevent Carrot Fly from Destroying Your Crop
The Guardian covers Carrot Fly
Horkans covers Kill Carrot Root Fly Organically
Not Just Green Fingers covers How to Avoid the Carrot Root Fly