Tomato blight, a fungal infection called Phytophthora infestans, spreads by wind and water-splash. It attacks tomatoes and potatoes and is triggered by warm, wet conditions, making outdoor tomatoes more susceptible than those in a greenhouse. The crop is quickly ruined and even if you pick the tomatoes at the first sign of infection, you can’t stop them rotting.
How to identify tomato blightSpread by airborne spores that can be carried over 30 miles on the wind, tomato blight is most prevalent when conditions are warm and wet. Outdoor tomatoes are more susceptible to blight than those growing in a greenhouse.
When affected by blight, ripening tomatoes develop brown sunken spots, which spread to the leaves and stems.
In this video, Monty Don explains what to do if blight affects your tomatoes, and explains whether you can still eat the tomatoes growing on blight-infected plants:
How to prevent tomato blight Keep tomatoes dryGrow tomatoes in a greenhouse or polytunnel if possible, as this will keep the leaves dry and help fruits ripen sooner than those grown outside.
Never plant tomatoes in soil or compost that has previously contained diseased plants.
Support tomato plants with a stake, including bush varieties, to keep their leaves off the soil.
If growing tomatoes outside and blight hits, try placing an umbrella of polythene or a plastic roof over tomatoes to keep the rain off them. This will stop rain splashing onto the leaves and reduce the likelihood of infection.
When watering tomatoes, water in the morning, so the plants don’t sit damp all night. Take care to water only the soil or compost, keeping the leaves dry. Remember, tomatoes taste better if the plants aren’t overwatered.
Feed tomatoes with fertilisers
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