We're having a lot of trouble with diseases in tomatoes. Leaves turn brown from the bottom of the plant and move upward. Is it a blight or a wilt? We've moved the plants and rotated them to a new location in the garden but this hasn't helped. So now we're thinking about creating raised beds. Will that help if these are soil fungi?
These are soil-borne fungi. They infect plants through rain splash, starting with the lower leaves and working their way up the plant. Creating a raised bed might help as long as you're using new soil. But it may not eliminate the problem forever. Pick off any infected leaves as soon as you notice them and dispose of them. Make sure that there's good air circulation, avoid over-head watering, and mulch around the plant to reduce rain splash.