Caused by one of three races of the fungus Fusarium oxysporum, this warm weather disease affects peppers, eggplant, potatoes, and legumes as well as tomatoes, and survives on weeds such as crabgrass, pigweed, and mallow. The first signs of the disease is the one-sided wilting of the lower leaves and loss of their green color. This is followed by the whole plant wilting, turning yellow (rarely brown), and dying. The fungus enters the plant from the soil through wounds in the roots and travels up the vascular system of the plant, blocking the water-conducting vessels. Although the exterior surface of the stem may show no signs of decay, if cut lengthwise it will have red to dark brown discoloration in the vessels. The disease thrives when the soil is about 82 F and is especially severe when the soil is acidic. It remains in the soil from year to year and can be spread by contaminated plant debris and equipment.
Control:
- Remove infected plants immediately and dispose of them to reduce the spread of the fungus.
- Wash tools, hands, and clothing that may have had contact with the disease and so can spread it.
- Use a 3 year crop rotation scheme with crops from other plant families
- Remove and dispose of above ground crop residual at the end of the growing season.
- Use resistant varieties noting that varieties differ in regard to their resistance to the three races of Fusarium.
- Raise the soil pH to 6.5-7 by applying lime
- Avoid excessive nitrogen and use calcium nitrate fertilizer instead of ammonium nitrate