Wilt occurs when the stems and leaves of a plant droop because they are not receiving enough water. In extreme cases, the leaves turn yellow and die. Common causes of wilt include drought and diseases caused by certain fungi and bacteria.
Fungi and bacteria cause wilt by plugging the xylem vessels of plants. Xylem vessels are channels that carry water from the roots to the leaves. The most common wilt-causing fungi are species in the groups Fusarium and Verticillium. Fusarium fungi cause wilt in many fruits and vegetables, including bananas, peas, and tomatoes. Verticillium fungi affect a wide variety of plants, including many flowers, crop plants, and trees. Dutch elm disease is a wilt disease that occurs when Ceratocystis ulmi fungus causes blockage of xylem vessels in elm trees. This fungus is spread by two kinds of beetles (see Dutch elm disease ). Bacteria that cause wilt in plants include species in the groups Pseudomonas and Erwinia.
The best way to prevent wilt is to plant crop varieties resistant to wilt-causing fungi and bacteria. Once established, wilt can be hard to control. Crop rotation usually will not prevent fungal wilt because the fungi can survive in soil and on plants in which they do not cause wilt. Trees infected with Dutch elm disease may need to be destroyed to keep the fungi from spreading to uninfected trees.
