Powdery mildew on carrot
The fungus Erysiphe heraclei coats the foliage in a white, powdery bloom. It turns up in the second half of summer, especially in dry spells, and limits how big the storage root grows.
Symptoms
- A white, powdery bloom on leaf stalks and blades
- The bloom first on older leaves, then across all the foliage
- Leaves yellowing and drying under the bloom
- Foliage dwarfed and flopping over
- Small black fruiting bodies in the bloom late in the season
What it does to the crop
- Reduced photosynthesis and smaller roots
- Machine harvesting made harder by the ruined foliage
- Lower sugar content and poorer flavour
- Weakened plants that are more prone to other diseases
What encourages it
- Warm, dry days with cool, damp nights
- Temperature 20-27°C
- Dried-out soil and water-stressed plants
- Growing on sheltered sites out of the wind
Prevention
- Water regularly and generously in dry spells
- Keep nitrogen feeding moderate
- Keep to the recommended row spacing
- Grow less susceptible varieties
- Clear the foliage away after harvest
⚠️ Before you reach for a spray
This atlas is informational and still growing — different diseases can look almost identical. Confirm the diagnosis and read the product label before applying any plant protection product. If you are unsure, ask your local extension or advisory service.
Keep the disease atlas with you in the garden
In the app you can identify a disease from photos, work out the spray dose for your own bed and log the treatment in your task calendar. Free, no sign-up, works offline.
Open the atlas in the app →