Carrot Fly
Pest · Commonly affects: Carrots, Parsnips, Celery, Celeriac, Parsley, Coriander, Chervil
Carrot fly is a small, low-flying pest whose larvae damage roots of carrots and related crops. It is widespread in UK gardens and allotments, with attacks often increasing after thinning or handling plants releases their scent. Crops may look healthy until roots are lifted, making prevention especially important.
How to identify it
The adult is a small, dark fly, about 4 to 5 mm long, with a reddish head and yellowish legs, but it is rarely seen because it flies close to the soil. The creamy white larvae are legless maggots, around 8 mm long, and tunnel through roots. Look for rusty brown tracks around carrot roots, wilting foliage or leaves turning reddish purple. Damage commonly appears in patches rather than evenly along a row.
Damage
Larvae tunnel beneath the skin and into the centre of roots, leaving rusty, brown galleries. Damaged carrots may become misshapen, bitter or prone to rotting, and are unsuitable for storing. Seedlings can wilt or die in severe attacks. Parsnips, celery and celeriac can also suffer, so nearby host crops may maintain the problem.
Prevention
Use a fine mesh barrier around 60 cm tall, or cover rows with fleece or fine insect mesh before adult flies are active. Keep all edges sealed. Sow thinly to avoid thinning, or thin in the evening and remove thinnings from the plot immediately. Rotate carrot-family crops to a different bed where possible, keep the area weed-free and choose resistant carrot varieties. Avoid placing carrots beside parsley, celery or celeriac in a small plot.
How to manage it
Lift and inspect any plants showing red or wilting foliage, removing affected roots and nearby crop residues from the plot. Maintain the 60 cm fine mesh barrier or fleece throughout the vulnerable period, replacing it promptly after watering or weeding. Harvest mature roots without delay if tunnelling is found. Do not compost badly damaged roots near the growing area. Plan a later sowing in a protected bed for a clean autumn crop.
Carrot Fly: frequently asked questions
How do I identify carrot fly?
The adult is a small, dark fly, about 4 to 5 mm long, with a reddish head and yellowish legs, but it is rarely seen because it flies close to the soil.
How do I prevent carrot fly?
Use a fine mesh barrier around 60 cm tall, or cover rows with fleece or fine insect mesh before adult flies are active.
How do I get rid of carrot fly?
Lift and inspect any plants showing red or wilting foliage, removing affected roots and nearby crop residues from the plot.
General guidance for UK home gardens and allotments, focused on prevention and non-chemical control. For a confirmed diagnosis, the RHS or a local garden centre can help. Page updated 19 Sep 2026.