So sorry about the blight that infected your tomatoes and potatoes. The blight needs three things to spread: the spores (they can last years in the soil), the host plant, and moist foliage. The practical way to avoid this next year is to keep the foliage of your plants as dry as possible by using a plastic covering such as a mini greenhouse. Another idea is to grow them under the eaves of the house to keep the rain from wetting the foliage. You can turn the soil over to help aerate it and bury spores this fall but this will not prevent another outbreak if you grow potatoes and tomatoes in the same spot. Move them at least 10 feet away from the outbreak. Good luck, Marianne Binetti