There is no foliage or it is turning yellow and wilts. Discard roots that show decay. Lower leaves turn yellow and wilt. Only one side of the plant may be affected. When the stem is sliced open dark streaks may be visible.
Disease enters through the roots and plugs water conducting vessels.
Destroy infected plants. Use plants that are resistant to Fusarium and Verticillium Fungi. Leaves and stems wilt. White fungus may encircle the stem. Plant roots rot.