📌 Editor’s Note: Combating Root Flies
- 🌍 The Pests: The Onion Fly (Delia antiqua) and the Carrot Rust Fly (Psila rosae) are notorious pests that lay eggs near the base of your crops. Their larvae (maggots) burrow into the roots, ruining the harvest.
- 🛡️ Organic Controls: This article covers traditional Eastern European organic remedies, including strong-smelling herbs, tobacco dust, birch tar, and companion planting. Note: The article mentions using mothballs (naphthalene) and salt water—while historically used, these are not recommended in modern organic gardening due to soil toxicity, but the other physical barriers and scent-masking tips are highly effective!
| Pest | Target Crops | Key Damage | Best Organic Controls |
|---|---|---|---|
| Onion Fly Delia antiqua |
Onions, Shallots, Garlic, Leeks | Larvae tunnel into bulbs, causing yellowing and root rot. | Birch tar soak, tobacco dust + wood ash, planting near carrots. |
| Carrot Rust Fly Psila rosae |
Carrots, Parsnips, Celery, Parsley | Maggots burrow rust-colored tunnels through taproots. | Floating row covers, onion skin infusion, planting near onions. |
In early spring, just as the orchards burst into beautiful bloom, the onion and carrot flies begin their sinister flight! ✈️ Judging by the names of these “lovely” creatures, it doesn’t take a detective to figure out exactly who they harm the most and who considers them the ultimate nemesis! ☠️
The Onion Fly
The onion fly lays its eggs right in the onion bed—either directly in the soil between the rows or right on the neck of the onion bulbs. Within a week, the larvae hatch. These onion maggots burrow inside the bulbs, where they have both “room and board” waiting for them.
The onion fly itself is slightly larger than the carrot fly, about 1/4 inch (6-7 mm) long. The larva reaches up to 3/8 inch (10 mm) in length. It overwinters in the pupal stage inside an elongated, egg-shaped puparium about 7 mm long. To survive the winter, it burrows into the soil to a depth of 6-8 inches (15-20 cm).
How to tell when the flies are swarming?
The emergence and flight of the fly coincide with the blooming of cherry trees and dandelions. In northern regions, it only manages to produce one generation per year. In the south, it can produce up to three generations!
Methods of Control
The fight against the fly must begin at planting time. Treat your onion sets in a potassium permanganate solution. Make a weak, pale-pink solution in warm water (105-120°F / 40-50°C) and soak the bulbs for 20-30 minutes. After planting, dust the beds with a mixture of tobacco dust and wood ash. Use one cup of ash and one tablespoon of tobacco dust per square meter (approx. 10 sq ft).
Some people treat the soil with sand or compost mixed with crushed naphthalene (mothballs).
Flies hate pungent odors. You can lay fresh wormwood, yarrow, or tomato leaves between the rows. After thinning your carrots, you can take those carrot tops and lay them across your onion beds. Or set out small, unneeded containers filled with creolin or tar oil.
You can also spray the plants with herbal infusions:
- Take 9 lbs (4 kg) of tomato leaves, pour 2.5 gallons (10 liters) of water over them, and boil for half an hour. Add a little liquid soap to act as a surfactant (sticker). Spray in the evening to prevent the sun from burning the wet leaves.
- Steep 7 oz (200 g) of tobacco dust in 2.5 gallons (10 L) of hot water for two days, strain, and spray.
Some gardeners water the beds with a salt and permanganate solution. To a bucket of pale-pink permanganate water, they add 10-14 oz (300-400 g) of table salt. Dissolve well and water the beds every ten days.
The Carrot Rust Fly
Right around the same time the onion fly takes off, the carrot rust fly begins its flight. This fly is smaller, up to 1/5 inch (5 mm). Its larva is roughly the same length.
The carrot fly lays its eggs at the base of the carrot stem. About a week later, the larvae burrow inside the root and tunnel through it. The carrot leaves will start to turn yellow. It is best to immediately pull up and destroy such carrots.
Carrot fly larvae die in dry environments. Therefore, it is better to water carrots rarely, but deeply. In a constantly wet, frequently watered bed, the moisture-loving larvae will thrive.
Thinning and weeding are mandatory steps when growing carrots. However, when you thin carrots, the bruised foliage releases a strong scent, and the flies react actively to this smell. Therefore, either right before or immediately after thinning, you should treat the bed with an infusion of tobacco dust or onion skins.
To make an onion skin infusion: take 14 oz (400 g) of dry onion skins, cover with hot water, and let it steep for a couple of days. Strain and spray.
You can also scatter dry onion skins right in the aisles. Just like with the onion fly, you can spray the carrots with infusions of wormwood, tomato leaves, or yarrow. Sprinkle the aisles with dry mustard powder, tobacco dust, or ground black or red pepper. Use a tablespoon of mustard or tobacco dust per square meter, or a teaspoon of ground pepper for the same area.
Immediately remove any thinned or pulled carrots from the garden bed so the scent doesn’t attract flies.
Some gardeners use an infusion of orange peels during thinning to confuse the flies. Just make sure to remove the peels from the garden afterward. Some people have noticed that throwing citrus peels into the compost bin drives away earthworms (though this information needs testing to be fully confirmed or busted).
In the spring, when the plants still need nitrogen, you can spray the beds with a solution of household ammonia—one or two tablespoons per 2.5 gallons (10 L) bucket of water. This spray repels flies and acts as a quick nitrogen foliar feed for the plants.
If you cover your beds in the spring with a floating row cover (spunbond), you can completely avoid the fly invasion. The plants will be warm underneath, and the flies cannot lay their eggs through the fabric.
The methods of fighting both flies are practically identical. The only real difference is that the onion fly is repelled by the scent of carrot tops, and the carrot fly is repelled by the smell of onion skins. That is why almost every gardener knows the classic companion planting trick: planting onions and carrots together in the very same bed!
💬 Grower Comments & Discussion
The flies look so cute in the pictures, it almost makes you not want to get rid of them 🙂
Yeah, agriculture is a harsh business… the path to a farmer’s happiness is paved with the carcasses of pests and moles 🙄
Great recommendations. Thanks for the advice. We’ve been suffering from this monster for two years now.
It’s either us or them.
When I thin my carrots, I douse the bed in cheap perfume. I buy the most nuclear-strength, stinky, cheap perfume I can find. The smell wafts from the bed across the entire property. Forget the flies, even the neighbors are stunned.
Tatyana123415 said:
When I thin my carrots, I douse the bed in cheap perfume…
Does it only last until the first watering?
I don’t quite understand the question. Whether it’s the first watering or no watering at all (if the rain takes care of it), I perfume the bed right when I thin them. I only thin carrots twice a season. Onions, I pull constantly. If I pull an onion—I spray. I used to scatter orange peels, but citrus has too delicate of a scent.
I just didn’t think perfume was that durable. Does the scent really stick around after it rains, for example?
It really does. They eventually fade after about 2 days minimum. The nastier the perfume, the longer it holds on!
And how do bouquets of stuffed toys affect the carrot fly? Is this a new trend in gardening? 😂 (Editor’s note: joking in response to a spam comment)
I soak my onion sets in a solution of birch tar, and I water the bed with tar water before planting. Then I cover the bed with floating row cover (spunbond) until they sprout.
Hello, I’m new to the forum) My name is Anastasia. When planting onions and carrots, I added mustard seed meal. I really liked the result) For carrots, I sprinkled it right into the furrows, then added the seeds, and scattered the remaining meal over the top of the bed once everything was sown. And I put it on top of the onions before burying them.
Pavlova Anastasia said:
And I put it on top of the onions before burying them.
I didn’t quite get that phrase))) How does that work?
I’m so sorry) I was watching my daughter and didn’t proofread my text before hitting send. I make holes to plant the onion sets, place the onion inside, sprinkle the mustard seed meal directly over it, and then cover it all with soil.
Good evening everyone! One kind lady from our forum named Tatyana gave me a tip, and I want to say a huge thank you to her: splash some birch tar directly into the bag with your onion sets, shake it up, and leave it for an hour or two. The flies really are gone. At least, I completely got rid of the plague!
