Optimal Conditions
Damp, humid conditions, usually when warm
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Discoloured, yellowing leaves that also typically curl up
Prevention
As damp, humid conditions greatly increase the potential for this disease, correct watering and spacing of your plants is paramount. Try to use drip irrigation instead of fan spray so that the soil and its roots are watered rather than the foliage. The disease may be carried in the seed, so source from a reputable supplier and don’t save seed from affected plants the year before. Crop rotation is also advisable.
Coping
Pick off the affected leaves and if the plant looks terminal dispose of it. Bicarbonate of soda (baking soda) and milk sprays will have some effect on containing it, as will a compost tea made with worm wee or compost juice.
Eradicating
Disposing of the affected leaves and plants is the only way to eradicate the disease.
