Asparagus: Fusarium Wilt

Problem
The growing shoot turns yellow to dingy brown and wilts. During wet weather, white or pink cottonlike strands often appear under the leaf scales. Wilting is most severe among full-grown plants during the months of July and August. When the infected plant is dug up, all or part of the root system is seen to be a reddish color. The plant eventually dies.

Analysis
This wilt disease is caused by a fungus (Fusarium species). Asparagus plants under stress from poor growing conditions (drought, poor drainage, insect or disease injury, etc.) are more severely affected. The fungus lives on organic matter in the soil. The disease is spread by contaminated seeds, plants, soil, and equipment; it often enters a garden on the roots of a transplant. The fungus enters the plant through the roots and spreads up into the stems and leaves through the water-conducting vessels in the stems. The vessels become discolored and plugged, cutting off the flow of water to the leaves. Because fusarium is favored by wet weather and warm temperatures (70° to 85°F), the fungi build up in warm soils. For more information about fusarium wilt, see Verticillium or Fusarium Wilt.

Solution
No chemical control is available. It is best to destroy infected plants. Next year, plant healthy crowns where asparagus has not been planted for 2 to 4 years. If you plant in infected soil, fumigate the soil about 3 weeks before planting. (For more information about soil fumigation, see Soil Fumigation and Solarization.)