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Fusarium Wilt

Plant disease · Fusarium oxysporum species complex

Description​

Fusarium wilt is a soilborne fungal disease that affects many garden crops and ornamentals, including tomatoes, beans, melons, and flowers. It is most commonly caused by members of the Fusarium oxysporum species complex. Different strains tend to infect particular hosts, so Fusarium wilt in one crop does not necessarily threaten every plant nearby. The fungus enters through roots and grows in the water-conducting tissue. As that tissue becomes blocked, the plant struggles to move water to its leaves even when the soil is moist. Symptoms often begin on older leaves and may affect one side of a plant or a single branch before spreading. Warm soil commonly favors disease development. The fungus can survive for years in soil and plant debris, and it can move with contaminated soil, transplants, tools, or water. Once a plant is infected, the disease cannot be cured.

Symptoms​

  • Yellowing leaves
  • Wilting
  • Stunted growth
  • Leaves dropping

How to Identify​

Look for yellowing and wilting that begin on older leaves, sometimes on just one side of the plant, while the soil remains adequately moist. Cut a lower stem lengthwise: brown streaks or a brown ring in the water-conducting tissue support a diagnosis of vascular wilt. Unlike ordinary drought stress, the plant does not recover reliably after watering. Unlike many root rots, the roots need not be soft or mushy early in the disease. Verticillium wilt and other vascular diseases can look very similar, so a plant diagnostic laboratory may be needed to confirm Fusarium and identify the cause.

Prevention​

Choose cultivars labeled resistant to the Fusarium wilt strains known to affect your crop; resistance labels are often crop- and strain-specific. Start with healthy seed and transplants, and use clean potting mix. Avoid moving soil from affected beds on tools, shoes, or equipment, and clean tools after working with suspect plants. Remove infected crop debris rather than incorporating it into the soil. Keep plants vigorous with appropriate watering and drainage, and avoid root damage when cultivating. Rotate susceptible crops where practical, but do not rely on rotation alone: the fungus can persist in soil for many years. In warm, sunny climates, soil solarization may reduce the amount of fungus in a small bed, though it may not eliminate it.

Treatment​

First, check soil moisture and roots to rule out a watering problem or root rot. If Fusarium wilt is likely, keep the plant evenly watered to reduce stress, but understand that watering will not stop the infection. Remove severely affected plants, including as much of the root system as practical, and dispose of them without adding them to a home compost pile. Clean soil from tools before sanitizing them, and avoid carrying soil to other beds. Do not replant a susceptible variety in the same spot; use a resistant cultivar, a suitable resistant rootstock, or a clean container with fresh potting mix. For a small affected area, soil solarization during a sufficiently hot, sunny period may lower future disease pressure. Fungicide sprays do not cure plants once the fungus is inside their vascular tissue; there is no reliable chemical rescue treatment.

Plants Affected​

Banana, Basil, Black-eyed Pea, Carnation, Chickpea, Cumin, Date Palm, Fenugreek, Gladiolus, Lisianthus, Okra, Pea, Plantain, Queen Palm, Snap Pea, Snow Pea, Sweet Pea, Watermelon

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