This fungal disease most often affects tomatoes, but may also be found on eggplant, peppers, potatoes, peas and squash family crops. It enters a plant through natural openings and wounds in the roots and grow up into the stem, where it blocks the supply of nutrients and water to the leaves. The first indication of infection is when a part of the plant starts to wilt on sunny afternoons, though it usually recovers when the temperature drops (this often starts to happen when plants begin bearing fruit). Eventually the infection spreads through the whole plant, lower leaves turn yellow (and may eventually die) and the stem becomes discolored. Plants don’t always die, but it slows growth and reduces yields. Fusarium is rarely a problem for commercial growers because most modern tomato varieties have been bred to be very resistant. If you stick with resistant varieties you don’t have to worry about it either. Many of the older heirlooms don’t have any resistance, so if you grow these then you should keep an eye out for it. Fusarium Wilt is most problematic in warm and wet conditions. To minimize its effects you should keep the plants well fed and watered. Mulch can also help by keeping the soil cool. If any plants start to show symptoms of partial wilting you should remove them immediately to reduce the spread of this disease. The spores can survive in the soil for up to 7 years.
Image: Howard F. Schwartz, Colorado State University, Bugwood.org