Fusarium Wilt

• Yellowing that begins on one side of the plant or one branch, not uniformly
• Wilting that does not recover overnight — unlike drought stress
• Brown discoloration in the vascular tissue when you cut the stem lengthwise — a salmon to brick-red interior
• Plants may die branch by branch over several weeks
• No visible signs of root rot at the soil surface

Fusarium oxysporum is a soil-borne fungus with host-specific formae speciales (races) for each crop. It can persist in soil for many years as chlamydospores. The pathogen enters through roots and grows in the vascular system, blocking water transport. Warm soil temperatures (above 75°F) and acidic pH favor disease development. Once Fusarium wilt is in a bed, it tends to recur in subsequent seasons in that spot.

1. 01There is no cure once a plant is infected — remove and dispose of infected plants to reduce inoculum
2. 02Plant resistant varieties — look for 'F' or 'FF' in variety codes (two races of Fusarium wilt resistance)
3. 03Solarize the bed with clear plastic in summer to reduce soilborne inoculum
4. 04Rotate crops: avoid planting the same family in an affected bed for at least three years
5. 05Raise soil pH to 6.5-7.0 — slightly acidic conditions favor the pathogen
6. 06Avoid high-nitrogen fertilizers: excessive ammonium nitrogen can increase susceptibility

If this keeps happening in your garden, the single most effective change is often the seed packet. These varieties carry documented resistance.

If Fusarium wilt is killing resistant varieties or occurring in a bed you've rotated out of solanaceous crops, an extension plant pathologist can confirm the diagnosis, identify the race, and advise whether soil solarization or biofumigation would be worth trying.

• Fusarium Wilt of Tomato— University of Minnesota Extension
• Fusarium Wilt— Clemson Cooperative Extension