How to Keep Carrot Fly Away With the Right Carrot Fly Netting

Growing your own carrots connects you directly to the rhythms of the soil and the real work of producing food. You choose the varieties, tend the crop, and know exactly what’s gone into them. But there’s a catch. Carrot fly can decimate an entire row before you’ve even noticed the damage, turning what should be a satisfying harvest into a frustrating writeoff. Proper carrot fly netting is one of the most reliable ways to protect your crop without resorting to chemicals, and it’s something I’ve relied on for years.

The relationship between grower and produce matters. When you’re nurturing carrots from seed to plate, you’re doing what small-scale producers across the country do every day. They face the same pests, the same weather, the same choices about how to protect their crops. Understanding carrot fly netting isn’t just about saving your own harvest. It’s about appreciating the skill and care that goes into the carrots you might buy from a local grower at a farmers’ market or through a veg box scheme.

Why This Matters

Carrot fly (Psila rosae) is the single most destructive pest for carrot growers across Britain. The adult flies are small, dark, and easily overlooked, but their larvae tunnel into the roots of carrots, parsnips, celery, and parsley, leaving brown scars and making the vegetables inedible. Once you’ve seen a carrot riddled with those characteristic rust-coloured tunnels, you’ll understand why prevention is essential.

The flies are active from late spring through autumn, with typically two or three generations appearing throughout the growing season. They’re low-flying insects, rarely rising more than 45cm above ground level, which makes physical barriers remarkably effective. I’ve found that netting works better than anything else I’ve tried, and it’s the method many commercial growers favour when they want to avoid insecticides.

What makes carrot fly particularly frustrating is that you often don’t realise you have a problem until harvest. The foliage looks fine, the plants seem healthy, and then you pull up your crop to find it ruined. By that point, it’s too late to do anything. That’s why I always tell people that carrot fly netting isn’t optional if you want a reliable harvest. It’s a fundamental part of growing carrots well.

Beyond protecting your own crop, using netting reduces the population of carrot fly in your area, which benefits neighbouring growers. It’s a small example of how individual growing practices connect to the broader community of food production. When you choose physical barriers over sprays, you’re making a decision that aligns with the principles many small producers work by: protecting crops whilst maintaining soil health and avoiding unnecessary chemicals. You might also find my guide on how to grow salsify helpful.

Getting Started

Choosing the Right Mesh

The effectiveness of carrot fly netting depends entirely on the mesh size. Carrot flies are small, but not microscopic. You need a mesh fine enough to exclude them but not so fine that it restricts airflow or light. The standard recommendation is a mesh size of around 0.8mm to 1.35mm. I’ve used both, and whilst the finer mesh offers slightly better protection, the 1.35mm works perfectly well for most situations and allows better air circulation.

Enviromesh is the type I see most often used by both home growers and commercial producers. It’s a woven polypropylene material that’s lightweight, durable, and lets through about 90% of available light. The weave is tight enough to keep out carrot fly, aphids, and even flea beetle, making it useful for brassicas as well. It typically lasts three to five years with proper care, though I’ve had pieces that have gone longer when stored correctly over winter.

Don’t confuse carrot fly netting with butterfly netting, which has a much larger mesh. That’s designed to keep out cabbage white butterflies but won’t stop carrot fly. Equally, avoid ultra-fine mesh intended for aphid exclusion unless you’re dealing with multiple pest problems, as it can reduce light levels and trap excessive moisture, particularly in our damp climate.

Installation Timing and Method

The timing of installation is critical. You need to get the netting in place before the first generation of carrot flies becomes active, which is typically from mid-April onwards. I prefer to cover my carrots immediately after sowing or thinning, as the scent released during thinning is particularly attractive to the flies. If you’re transplanting module-sown carrots, cover them the same day.

Create a physical barrier that extends all the way to the ground with no gaps. I use hoops made from alkathene water pipe or bamboo canes bent into arches, spaced about 60cm apart along the row. The netting drapes over these hoops and is secured at ground level with soil, bricks, or planks. The key is ensuring there are no entry points. Even a small gap will allow flies in, and once they’re under the netting, they’re trapped with your crop.

Height matters because carrot flies are weak fliers that stay close to the ground. A vertical barrier of at least 60cm is often cited as sufficient, but I prefer to use hoops and fully enclose the crop. This method also protects against other pests and provides some shelter from wind. In exposed areas, you’ll need to secure the netting firmly, as strong winds can lift edges or collapse poorly supported structures.

Dealing with Edges and Ends

The ends of your netting are the most vulnerable points. I’ve seen people carefully cover the length of a row only to leave the ends flapping open. You need to gather the netting tightly at each end and secure it thoroughly. I use clothes pegs or clips to bunch the material, then weight it down with something heavy. Some growers sew the ends closed, which works brilliantly if you’re not planning to access the crop regularly.

Where the netting meets the ground along the sides, bury the edge under at least 5cm of soil or weight it down continuously. Don’t leave sections held down with just a few bricks with gaps in between. Carrot flies will find those gaps. I’ve learned this the hard way after losing half a row because I was lazy with the southern edge of my bed.

Advanced Tips

Managing Access for Weeding and Harvesting

One challenge with carrot fly netting is that you need to access your crop for weeding, thinning, and eventual harvest. Every time you lift the netting, you create an opportunity for flies to enter. I’ve developed a routine that minimises this risk: I only open the netting early in the morning or late in the evening when carrot flies are least active. They prefer warm, still conditions, so working during cooler or breezy periods reduces the chance of letting them in.

When you do need to weed or thin, work quickly and methodically. Lift just one section at a time rather than exposing the entire row. I keep a bucket of water nearby to immediately submerge any thinnings, as the scent of damaged foliage is what attracts the flies most strongly. Don’t leave thinnings lying on the ground or in your compost bin near the growing area. I either drown them or dispose of them well away from the vegetable patch.

For regular harvesting, consider creating a permanent framework with a door or panel that can be opened and closed. This is particularly useful if you’re growing storage carrots that you’ll be pulling throughout autumn and winter. A simple wooden frame covered with mesh, with one removable side, gives you easy access whilst maintaining protection. It’s more work upfront but pays off if you’re serious about carrot growing.

Combining Netting with Crop Rotation and Companion Planting

Carrot fly netting is most effective when combined with good cultural practices. Crop rotation is fundamental. Don’t grow carrots, parsnips, or other susceptible crops in the same bed year after year. Carrot fly pupae overwinter in the soil, and rotating crops helps break their lifecycle. I follow a minimum three-year rotation, which also helps manage soil fertility and reduces other pest and disease problems.

Companion planting has a mixed reputation, and I’m sceptical of some of the more optimistic claims. However, there’s reasonable evidence that interplanting carrots with alliums (onions, spring onions, chives) can provide some confusion to carrot flies. The strong scent of onions may mask the carrot smell. I’ve tried this, and whilst it’s not a substitute for netting, it seems to offer a modest additional benefit. It also makes efficient use of space.

Some growers advocate for planting late, after the first generation of carrot flies has finished. This can work, particularly in northern areas where there may only be two generations rather than three. However, it limits your growing season and doesn’t protect against the second and third generations. I prefer to use netting and sow when soil conditions are right, rather than trying to dodge the pest through timing alone.

Netting in Different Growing Systems

Carrot fly netting works in raised beds, traditional rows, and containers. In raised beds, you can build the framework into the bed design, creating a semi-permanent structure that’s quick to cover each season. I’ve seen excellent setups where the netting is attached to a hinged frame that folds back for access and closes securely. This is particularly useful for intensive bed systems where you’re maximising space and want easy management.

For containers, particularly deeper ones suitable for long-rooted varieties, you can create a simple cage using canes and netting. This works well on patios or in small gardens where space is limited. The key is ensuring the mesh extends below the rim of the container so flies can’t crawl underneath. Container growing has the advantage that you can move your carrots away from areas with high carrot fly populations, though that’s rarely practical for most people.

In allotment settings, coordinating with neighbours can make a real difference. If several people are growing carrots in adjacent plots, creating a larger protected area can be more effective than individual efforts. I’ve been part of allotment communities where we’ve pooled resources to buy netting in bulk and shared knowledge about installation techniques. This collective approach mirrors how market gardeners work, sharing insights and resources to improve outcomes for everyone.

Regional and Seasonal Variations

Carrot fly pressure varies across Britain. In southern England, you’ll typically face three generations of flies, with activity from April through to October. The first generation emerges in late spring, the second in midsummer, and a third in early autumn. Each generation is capable of causing significant damage, so netting needs to remain in place for the entire growing season until you’ve harvested your crop.

In northern England, Scotland, and higher altitude areas, you might only encounter two generations. The shorter growing season and cooler temperatures reduce the pest pressure slightly, but carrot fly is still a serious problem. I’ve spoken with growers in the Scottish Borders who have lost entire crops when they assumed the pest wouldn’t be an issue. Don’t rely on your location to protect you. Use netting regardless.

Coastal areas can experience different timing due to milder winters and the moderating effect of the sea. In parts of Cornwall and Devon, I’ve heard reports of carrot fly activity starting earlier in spring and extending later into autumn. Equally, very exposed coastal plots might see reduced pressure due to constant wind, which carrot flies dislike. However, this isn’t reliable enough to skip protection.

Seasonally, the highest risk periods are May to June for the first generation and August for the second. These are the times when I’m most careful about keeping netting secure and avoiding unnecessary access to the crop. The autumn generation is often less damaging, but it’s still worth maintaining protection, particularly if you’re growing maincrop varieties for winter storage.

Climate patterns influence carrot fly behaviour. Warm, still weather is ideal for the flies, whilst cool, wet, or windy conditions suppress their activity. The increasingly variable British weather makes it harder to predict exact timings, which is another reason why I advocate for season-long protection rather than trying to time netting installation to specific pest generations.

In Practice

In practice, many growers find that the initial effort of setting up carrot fly netting pays dividends year after year. The first time you install it, there’s a learning curve. You’ll probably make mistakes with securing the edges or leave gaps you don’t notice until later. But once you’ve done it a few times, the process becomes straightforward and quick. I can cover a 10-metre row in about twenty minutes now, including setting up the hoops and securing all the edges properly.

Growers consistently report that netting transforms their success rate with carrots. Without it, you might get a decent crop one year and lose everything the next, depending on pest pressure and weather conditions. With netting, you get reliable results. This predictability is what allows market gardeners and small-scale producers to plan their cropping and commit to supplying customers. When you buy carrots from a local grower, there’s a good chance they’ve used similar protection methods to ensure they can deliver quality produce consistently.

The durability of the netting surprises many people. With reasonable care, taking it down carefully at the end of the season, shaking off soil and debris, and storing it dry, you’ll get multiple years of use. Some growers wash theirs, which helps if you’ve had pest or disease issues, but I’ve found that simply drying it thoroughly before storage prevents most problems. Fold it loosely rather than cramming it into a tight space, as this reduces wear on the material.

Author: Megan Walker

Megan focuses on seasonal food, kitchen garden growing, and how households can reconnect with where their food comes from. Her writing blends practical growing advice with ideas for cooking and eating in season. With a passion for fresh ingredients and sustainable living, Megan’s articles help readers make the most of local produce while supporting British farms.