A fungal infection that causes the discolouration of leaves and can often be terminal to a plant, leaf blight is one of those diseases that sinks your heart. Often affecting your tomato crop, it is commonly referred to as tomato blight or potato blight, another crop it gravitates towards.

Blight will usually appear early in the season and is given away by yellowing or dying leaves. However, it will also strike around fruiting time and limit the plant’s ability to photosynthesise. Usually the result of damp, humid conditions, it is exacerbated by overcrowding crops and keeping the leaf foliage too wet.

If you notice blight on your cherished summer crop don’t be defeatist and pack it in. Some simple but tough measures – such as culling overcrowded plants and watering in the morning rather than at night – will greatly reduce the chances of further infestation.

Optimal Conditions

Damp, humid conditions, usually when warm


Discoloured, yellowing leaves that also typically curl up


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.


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.


Disposing of the affected leaves and plants is the only way to eradicate the disease.

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