This article provides practical guidance on the carrot fly (Chamaepsila rosae) – how to recognise it, where it is found in the UK, how to avoid infestations, and how to control or eliminate it in gardens, allotments, and storage areas.
In the UK, the pest is known primarily as the carrot fly, but it is also occasionally referred to as carrot root fly or carrot rust fly.
What does a carrot fly look like?
The adult carrot fly (Chamaepsila rosae) is a small, slender fly measuring around 4–5 mm in length. It has a shiny black body, reddish-brown head, long legs, and clear wings. It is not especially noticeable and tends to stay close to the ground, particularly in calm, shaded environments.
The larvae – known as carrot fly maggots – are the destructive stage. They are creamy white, legless, and grow up to 10 mm long. These larvae tunnel into carrot roots, leaving behind brown or rust-coloured streaks and making the vegetables inedible or prone to rotting.
Where are carrot flies found in the UK?
Carrot flies are widespread throughout the UK, especially in areas with temperate climates and moist soil conditions. They are a common problem in domestic gardens, allotments, and small-scale commercial plots.
They are typically found:
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In vegetable patches growing carrots, parsnips, celery, or parsley
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In shaded garden beds with poor airflow
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Near compost heaps containing root vegetable waste
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In the same soil where carrots or similar crops have previously been grown
Where do carrot flies live and reproduce?
Carrot flies overwinter as pupae in the soil. In spring, adults emerge and lay eggs in the soil around the base of carrot plants. The female is especially attracted to the smell released when carrot foliage is disturbed or crushed.
Eggs hatch within a week, and larvae feed inside the roots for up to a month before pupating. In the UK climate, there are usually two generations per year – the first in spring and a second in late summer.
Carrot flies prefer:
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Cool, shaded areas with damp soil
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Raised beds or borders where airflow is limited
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Densely planted beds with other umbelliferous crops
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Untidy gardens with plant debris or decaying roots
How can you avoid carrot fly infestations?
Prevention is key when dealing with carrot flies, as larval damage is hard to detect until it’s too late.
Use insect-proof mesh
Cover carrot beds with fine mesh netting or horticultural fleece from the time of sowing until after the main flight period. This physically prevents egg-laying by adult carrot flies.
Rotate crops
Avoid growing carrots or other susceptible crops in the same spot for consecutive years. Pupae left in the soil can emerge the following season and reinfest the same area.
Sow resistant varieties
Some carrot cultivars, such as ‘Flyaway’ or ‘Resistafly’, have been bred for resistance to carrot fly damage. They are less attractive to egg-laying females and show reduced root damage.
Thin carefully
Thinning releases a strong scent that attracts carrot flies. Thin plants during the evening when fly activity is lower, and remove thinnings immediately from the garden.
Intercropping with deterrent plants
Growing carrots alongside strong-smelling plants like onions, garlic, or rosemary may mask the carrot scent and help reduce egg-laying.
How do you recognise carrot fly damage?
Carrot fly damage can be difficult to detect until roots are harvested. However, early signs may appear on the foliage.
Look out for:
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Reddish or purplish leaf edges
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Slowed or stunted growth
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Brown tunnels running through the carrot root
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Rotting or blackened areas near the crown of the carrot
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Presence of small, white larvae inside or on the surface of the root
Severe infestations can destroy entire crops, especially in late summer.
How do you get rid of carrot flies?
Remove affected crops
If damage is detected, remove and discard affected roots. Do not compost infested material, as larvae may survive and pupate.
Solarise the soil
During hot spells, cover the soil with clear plastic sheeting for a few weeks to raise soil temperature and kill pupae. This works best in southern regions or warm summers.
Encourage natural predators
Ground beetles, parasitic wasps, and birds may help control carrot fly populations naturally. Providing habitat for beneficial insects can support this approach.
Apply biological controls
Nematodes such as Steinernema feltiae can be applied to moist soil to infect and kill larvae. This method is most effective when applied early in the season or after sowing.
Use trap crops
Sow a sacrificial early batch of carrots to attract the first generation of flies. Remove and destroy the plants before the larvae hatch, helping to reduce pressure on the main crop.
Chemical treatment
There are limited chemical options available, and they are not generally recommended for home gardens. Where used, timing must coincide with peak adult activity. Always follow UK pesticide regulations and product labels.
What is the life cycle of the carrot fly?
The carrot fly undergoes a full metamorphosis:
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Eggs: Laid near the base of host plants, typically in spring and late summer.
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Larvae: Hatch and burrow into roots to feed for 2–4 weeks.
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Pupae: Develop in the soil, either emerging for the next generation or overwintering.
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Adults: Emerge in spring to start the cycle again.
In the UK, two generations per year are common, with adult activity peaking from May to June and again from late August into early autumn.
Can carrot flies cause problems indoors?
Carrot flies do not generally live or breed indoors, but they can cause problems if infested carrots are brought inside. Maggots inside the roots may continue feeding, leading to rot and spoilage during storage.
To avoid this:
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Inspect carrots before storage and remove damaged ones
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Store roots in a cool, dry, and well-ventilated place
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Clean storage containers between harvests
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Avoid storing carrots with damaged tops or bruised roots
Do carrot flies affect other crops?
Carrot flies primarily attack members of the Apiaceae (umbellifer) family, including:
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Carrots
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Parsnips
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Celery
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Parsley
These plants release similar root scents that attract egg-laying females. To minimise infestations, avoid planting multiple susceptible crops together and always practise crop rotation.