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Alternaria dauci

Alternaria dauci

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Alternaria dauci is a fungal disease affecting carrots in spring, summer, and autumn. Its primary vector is water, so is most severe during wet and humid weather. The oldest leaves are most susceptible, the main symptoms being sudden dark lesions, followed by the collapse of the foliage and ultimate death.
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Identification

Green brown lesions which become wetter, ultimately ending in necrotic lesions.

Growth factors

- Becomes active in spring, summer and autumn. - It's most severe during prolonged periods of warm and humid weather.

Symptoms

Green-brown lesions on foliage.
Necrotic lesions.
Young leaves are relatively untouched.
Sometimes, some foliage will die suddenly.
Damping off of seedlings.
Inflorescence infection.
Seed stalk blight.

Chemical treatment

Some copper bactericides can slow the spread of the disease, but it's not curable. If any product is purchased or used, check that it's authorised for use in your country or state. Always take care to read instructions and make sure that your edible crop is listed on instructions. Flowering plants shouldn't be sprayed.

Prevention

Make sure the seed you use is from a reputable source or business. You can bathe infested seeds in hot water for approx 25 minutes (above 50 degrees). Practise crop rotation. Keeping good plant and tool hygiene. Good pest control.

Affected plants

A bunch of orange Daucus carota subsp. sativus carrots

Carrot

Daucus carota ssp. sativus

Carrot

Daucus spp.

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