A slender, wasp-like fly with a black body, brown head and yellow legs lays its eggs in the soil beside young carrots, and the cream-yellow maggot that hatches burrows down to tunnel through the roots. Carrot fly (Psila rosae) rarely flies above 2 feet, so a net of that height is what keeps a crop clean.
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…
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.
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.
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.
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.
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.
At the time of sowing, add coffee grounds. The strong smell repels the fly, while being a choice fertilizer!
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.
The article describes several ways of keeping Psila rosae away from a carrot bed, some preventive and some used once damage has begun. This table sets them side by side so you can pick the one that suits your timing.
| Method | Type | When to apply | How it works |
|---|---|---|---|
| Crop rotation | Preventive | At the next sowing | Moves carrots well away from soil where pupae may still be overwintering |
| Anti-insect net | Preventive | From sowing onwards | A physical barrier about 2 feet (60cm) high, matching the fly’s maximum flying height |
| Allium companions | Preventive | At planting | Onion, leek and garlic grown alongside repel the carrot fly |
| Wormwood nearby | Preventive | At planting | Its scent repels the fly |
| Coffee grounds | Preventive | At the time of sowing | Strong smell repels the fly and feeds the soil at the same time |
| Lavender mulch | Preventive | At the time of transplanting | Laid at the base of the carrots so the fly will not lay there |
| Glue strips | Curative supplement | Once flies are about | Carrot-coloured traps set at flying height catch adults, but not enough on their own |
| Garlic or onion infusion | Curative | Sprayed on affected plants | Boiled and infused garlic preparation keeps the pests away, keeps cool for 10 days |
Combining a barrier with a repellent planting gives far better results than any single measure used alone.
Are your carrots already under attack? Consider removing all affected carrots and burning them. Here are two environmentally safe control methods.
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.
Still with the aim of keeping these pests away from the garden, prepare a garlic infusion.
You can keep this decoction cool for 10 days. To use it, just spray it on the affected plants.
