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Carrot leaf blight
Alternaria dauci
Fungal diseaseMedium impact
A fungal disease that causes dark lesions on carrot foliage, weakening plants and reducing root development. More common in warm, wet summers and where crops are sown densely.
Currently in peak season - extra vigilance worthwhile.
Key facts
- Type
- Fungal disease
- Affects
- Carrot
- Active season
- May - Sep
- Peak season
- Jul - Sep
- Vulnerable stages
- Growing · Harvesting
- Spread rate
- moderate
- If confirmed
- Act soon
Signs & symptoms
- -dark brown or black lesions with yellow halos on leaves
- -lesions often starting at leaf margins before spreading inward
- -leaves curling or dying back from tips
- -affected plants showing reduced vigour and slower root fill
Management
Do now
- -Remove and bin heavily affected foliage - do not compost
- -Avoid overhead watering to reduce leaf wetness
- -Improve airflow by thinning if plants are crowded
Prevention
- -Rotate carrots to a fresh bed each year
- -Space plants at recommended distances to allow airflow
- -Water at the base rather than over the foliage
- -Clear all carrot debris promptly after harvest
Further reading
- -Carrot leaf blight is usually worst when crops are stressed by drought or overcrowding - healthy, well-spaced plants are more resilient
- -The disease affects foliage, not roots directly, but severe leaf loss reduces root yield and quality