Fusarium wilt is a fungus that usually enters through the roots of plants. The lower leaves on one side of a plant turn yellow or brown then wilt. Branches die back until the entire plant succumbs. The vascular tissue turns brown. Hosts include asparagus, bean, cabbage, cantaloupe, pea, tomato, and watermelon.
Gardeners often make the mistake of assuming the problem is due to lack of water or fertilizers. Overwatering or excessive fertilizer will exasperate the problem.
There is no known cure for this disease. Try purchasing plants that are Fusarium resistant (usually has the letter “F” on the label). Plant on mounds or in raised beds in well drained soil. Rotate crops so that the same plant is not in the same location for at least 2 years. Avoid mixing undecayed organic material into the soil. Do not apply excessive nitrogen. Use calcium nitrate instead of ammonium based fertilizers.
Source: http://ipm.ucanr.edu/PMG/GARDEN/PLANTS/DISEASES/fusariumwlt.html
https://extension.umn.edu/disease-management/fusarium-wilt#cultural-control-3037561