Carrot fly, how to control this wasp-like carrot borer

Your carrot plants look sad? The roots are dug up and blackened? It’s probably the carrot fly! Discover how to fight this garden pest.

→ Also read:

• Growing carrots the right way
• Treating against onion fly

Meet Psila rosae, the Carrot Fly

This flying insect belongs to the psilidae family. This fly has a slender silhouette like a wasp.

Its body is black, its head is brown, its legs are yellow, and its wings are of a pale translucent yellow.

It’s its larva that causes problem in the garden! Measuring up to ~2/5 inch (1cm) long, it is of a cream yellow color. The issue? It particularly appreciates carrot roots…

Life Cycle

In the spring, flies lay eggs near young carrot plants. Each female lays about fifty eggs in the soil. Once the egg hatches, the larva buries itself in the soil to feed on the roots. They even end up digging tunnels, which significantly weakens the plant. The maggot then transforms into a pupa to pupate. After a short month, the pupa gives way to an adult insect.

Every year, two to three generations succeed each other. In winter, the pupae enter diapause underground, meaning they hibernate. The insects will then emerge from the ground the following spring, when the temperatures are more clement.

Symptoms and Damage to the Garden

Digging directly into the carrot itself, the culture is endangered, but especially the harvest! Your plants will then be weakened, wilted and the leaves will yellow.

In case of heavy attack, the plants will perish and the harvest will be compromised. When you pull up your carrots, you will then see the roots dug up and marked by black streaks.

How to avoid the carrot fly

Crop rotation:

This insect overwinters underground, near carrot plants, so it’s crucial to move the host plant. If you have already suffered an attack from this pest, consider significantly distancing your carrots during the next sowing. Indeed, there may still be pupae underground, even if you think you’ve eradicated all of them.

The anti-insect net:

As a preventive measure, install an anti-insect net that will act as a barrier to flies. This way, they cannot lay eggs at the base of the carrots. The fly flies at a maximum height of about 2 feet (60cm), remember to use a net of the same height.

Crop associations:

Some plants have a repelling effect on certain pest insects.

This is the case with Alliums such as onion, leek and garlic, which repel the carrot fly. A service rendered by the latter that keeps away the onion fly. It’s better to plant these two next to each other! You can also set up wormwood nearby, its scent repels the fly.

Coffee grounds:

At the time of sowing, add coffee grounds. The strong smell repels the fly, while being a choice fertilizer!

Lavender mulch:

While we appreciate lavender to the point of making scented sachets, this is not the case with the carrot fly. At the time of transplanting, place lavender mulch at the base of the carrots, the fly will not come to lay there.

Natural treatments against the carrot fly

Are your carrots already under attack? Consider removing all affected carrots and burning them. Here are two environmentally safe control methods.

Glue strips:

The same color as carrots, these strips work as a trap for the flies. Place them at flying height, so they can easily stick to them. This technique is a good supplement to eradicate them. However, it won’t be enough to deal with them on its own, especially if the attack is significant.

Garlic or onion infusion:

Still with the aim of keeping these pests away from the garden, prepare a garlic infusion.

1. Boil about 1 quart of rainwater or filtered water (1 liter)
2. Add about 3.5 ounces of crushed garlic (100 grams)
3. Keep boiling for 15 minutes
4. Cover and let infuse for 12 hours
5. Pour the preparation into a sprayer using a strainer to filter it

You can keep this decoction cool for 10 days. To use it, just spray it on the affected plants.