Chrysanthemum: Verticillium Wilt

Problem
Leaves yellow, wilt, and die, starting with the lower leaves and progressing up the plant. Older plants may be stunted. Leaf wilting and death often affect only one side of the plant. Flowering is poor. There may be dark brown areas on the infected stems. When the stem is sliced open near the base of the plant, dark streaks and discolorations of the water-conducting inner stem tissue are revealed.

Analysis
This wilt disease affects many ornamental plants. It is caused by a soil-inhabiting fungus (Verticillium species) that persists indefinitely on plant debris or in the soil. The disease is spread by contaminated seeds, plants, soil, equipment, and groundwater. The fungus enters the plant through the roots and spreads up into the stems and leaves through the water-conducting vessels in the stems. These vessels become discolored and plugged. This plugging cuts off the flow of water to the leaves, causing leaf yellowing and wilting. For more information about verticillium wilt, see Verticillium or Fusarium Wilt.

Solution
No chemical control is available. It is best to destroy infected plants. Verticillium can be removed from the soil only by fumigation techniques. (For more information about soil fumigation, see Soil Fumigation and Solarization.) However, the best solution is usually to plant flowers that are resistant to verticillium. For a list of verticillium-resistant plants, see Plants Resistant to Verticillium Wilt.