Few gardeners go through season after season without facing a soil-borne disease among their plants. Tomato growers know the drill. Fusarium wilt causes leaves on the bottom of the tomato plant to look scorched, wilt and then turn brown. Soon the plant becomes stunted or entirely bites the dust.
Verticillium wilt makes older leaves near the bottom of the plant wilt, yellow, dry and drop off.
To remove overwintering sites of disease to prevent the return in the spring, prune branches with lesions and cankers. Both are caused by soil-borne diseases. Warm temperatures and soil favor fusarium wilt, which attacks annuals, perennials, vegetables, melons, marigold, spinach and squash. Cooler weather promotes verticillium wilt, which also targets roses, strawberry and brambles, dahlia, trees such as catalpa, redbud and maple and many other ornamental landscape plants. Overfertilization and poor garden sanitation habits favor the problem.