Carrot Fly
Risk near you, next 48h
See whether your local forecast favours this disease right now.
When it strikes
Fix the cause, not the leaf
No spray will help here. The trigger is soil, water supply, nutrition or temperature, so change the growing condition and judge the result on new growth, not on damaged leaves.
Soil and crop debris
It waits in the ground or in last season's debris, so removing the plant does not clear the bed. Rotation and debris removal are the working controls.
It carries over to next season in soil, debris or seed — which is why rotation matters here, not just treatment.
Safe to compost
No pathogen carries over on this material, so it can go on an ordinary heap with the rest of the garden waste.
When and where to look
Scout the planting while temperatures hold between 12°C and 26°C.
Rule these out first
Same category, and at least one host crop in common — so they are genuinely confusable in the same part of the garden.
The signs that lead here
Full problem lists for these crops
About
Carrot fly (Psila rosae) finds its host entirely by smell, homing in on the scent released when carrot foliage is crushed or thinned. Its larvae then tunnel through the roots of carrots, parsnips, celeriac and parsley, ruining them for storage.
Symptoms
Foliage turns reddish then yellow and the plant looks stressed for no obvious reason. Lifted roots carry rusty-brown tunnels just under the skin, with small cream maggots inside. Damaged roots rot in store.
Organic Treatment
Cover the row with fine insect mesh from sowing to harvest — the low-flying adults cannot get over a 60 cm barrier or through mesh. Sow thinly to avoid thinning at all, and if you must thin, do it on a still evening and remove every trace of the thinnings.
Chemical Treatment
No effective garden insecticide reaches larvae inside the root. Timing a permitted soil drench to the two adult flight periods is unreliable and rarely justified when mesh works completely.
Prevention
Rotate away from umbellifers each year, delay sowing until early June to miss the first generation, lift maincrop before the second generation matures, and choose partially resistant varieties.
Crops at risk
Related problems
Carrot Fly risk by location
Each location has a month-by-month profile computed from the weather archive: how many hours a year actually meet this disease’s thresholds.