How to spot tomato blight and what to do about it

2021 has caused problems for smallholders with the unseasonably damp weather causing an increase in

2021 has caused problems for smallholders with the unseasonably damp weather causing an increase in tomato blight Credit: Okea/Getty - Credit: Getty Images/iStockphoto

Tomato blight has ruined many harvests in 2021; find out how to spot tomato blight, what causes it and how to treat it

The standout feature of blight is floppy leaves and a blackening of the stem
Cedit: Charles Dowding

The standout feature of blight is floppy leaves and a blackening of the stem Cedit: Charles Dowding - Credit: Charles Dowding

Blight is a disease to avoid if you can, for example, by using resistant varieties of outdoor tomatoes; prevention is better than cure here. With non-resistant strains, in damp weather leaves wilt and turn translucent as they die very rapidly.

An example of tomato blight
Credit: Liudmyla Liudmyla/Getty

An example of tomato blight Credit: Liudmyla Liudmyla/Getty - Credit: Getty Images/iStockphoto

What does tomato blight look like?

If you are not sure about recognising it, check the photos. Blight is not the only reason for leaves to show brown edges or spots. The standout feature of blight is floppiness of leaves, together with blackening of some stems.

What causes tomato blight?

Blight can occur even out of the rain in a greenhouse or polytunnel, from wetting leaves during watering, from rain blowing in, or from leaves being in contact with damp polythene.

What to do if you have tomato blight

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As soon as you see it, cut off all infected leaves in order to prevent spores from entering plant stems. If it does, tomatoes will turn brown and start to rot before or during ripening.

Potato blight

Check for blight on potato leaves. If the weather is still damp, it is best to cut the stems at ground level, then put all of the stem and leaves to compost. I always compost blighted material and the disease does not survive in a heap. Blight spores die in soil and compost once they have no more plant material to live off.

Potatoes can be left in the soil, but I suggest harvesting them before slugs start eating them and then you can plant more vegetables. Sarpo potato varieties resist blight. However, they require harvesting in late August before the tubers become too starchy.