Plant Problem Diagnostic
Fusarium Wilt (Fusarium oxysporum): Identification and Cultural Management
The short answer
Fusarium wilt is caused by the soil fungus Fusarium oxysporum, which enters through the roots and plugs a plant's water-conducting (vascular) tissue. Affected plants often wilt during the hottest part of the day and recover overnight at first, then yellow and wilt for good. Yellowing frequently starts on one side of the plant or even one side of a leaf, and if you slice open the lower stem you may see brown to reddish-brown streaking in the vascular tissue.
Once a plant is infected there is no cure, so management is preventive: plant resistant varieties, remove and dispose of infected plants, keep tools and soil from moving between beds, and rotate away from susceptible crops. Because each Fusarium strain (forma specialis) is usually adapted to a specific host, and because wilting has many causes, confirm the diagnosis with your local Extension or a plant diagnostic lab before making big decisions.
How to identify it
- Wilting that begins during heat and recovers at night, becoming permanent over time
- Yellowing often on one side of the plant or one side of a leaf
- Brown to reddish-brown streaks in the vascular tissue of a cut lower stem
- Symptoms worsen in warm soils, unlike some other wilts favored by cool conditions
Conditions that favor it
The fungus survives for years in soil and plant debris as tough resting spores (chlamydospores), so infested ground stays a risk long after a sick crop is gone. It is often introduced on infected transplants or carried on equipment moving contaminated soil.
Cultural management steps
- 1Plant resistant varieties — Many vegetable lines carry resistance to specific Fusarium races; check the variety description or seed packet for the appropriate resistance code.
- 2Remove infected plants — Pull and dispose of symptomatic plants; do not compost them, and avoid spreading their soil to clean beds.
- 3Clean tools and soil movement — Sanitize tools and avoid moving soil, mud, or debris from infested areas on shoes and equipment; follow the label on any sanitizer.
- 4Rotate crops — Rotate to non-host crops where practical, though rotation alone may not eliminate a long-lived soil pathogen.
When to escalate
Fusarium wilt looks a lot like Verticillium wilt and several root or vascular problems. If several plants collapse, if you are planning to replant the same bed, or if you cannot confirm the cause, submit a sample to your Extension plant diagnostic clinic for identification.
→ No fungicide cures a plant already infected with Fusarium wilt; label-directed products do not reverse vascular infection. Focus on prevention and confirmed diagnosis.
Sources
Reviewed 2026-07-18. We cite university Extension, government, and established horticultural sources — and never invent pesticide rates or dangerous treatments.
- Utah State University Extension — Fusarium and Verticillium Wilts of Vegetables — Symptoms (daytime wilt, one-sided yellowing, vascular discoloration), chlamydospore survival, no cure, resistant varieties and cultural control
- University of Minnesota Extension — Fusarium wilt — Fusarium oxysporum is soilborne and host-specific by forma specialis; management is preventive