Blight is a disaster for tomatoes, but there are ways to avoid it to ensure a healthy crop. Tomato blight thrives in warm, humid conditions, so our wet summers are the perfect environment. When there's blight about, you can't completely protect tomato plants, but you can decrease the risk of them catching it if you act early.
Begin by thoroughly cleaning your greenhouse or polytunnel to ensure it's free from overwintering spores. Outdoors, dig through the soil to check there are no potatoes left in the ground as these may harbour blight that can spread to the next potato and tomato crops.