Fusarium Wilt
Fusarium oxysporum (various formae speciales)
Overview
Fusarium wilt is a soil-borne vascular disease caused by host-specific forms of Fusarium oxysporum. The fungus enters roots, colonizes xylem, and blocks water flow, producing progressive yellowing, one-sided wilt, and death. Chlamydospores and other survival structures can persist in soil for many years, so short rotations rarely clear a bed. Resistant cultivars, grafting, soil health practices, and careful sanitation are the realistic tools for organic and permaculture growers facing this pathogen.
Symptoms
Wilting often begins on one side of a plant or on lower leaves and progresses upward even when soil moisture looks adequate. Leaves yellow, then brown, and may drop. Cutting the stem lengthwise often reveals brown streaks in the vascular tissue. Plants stunt, set poorly, and eventually collapse. Cool nights may temporarily firm wilted tissue, but decline resumes as days warm.
Environmental Conditions
Hot
Prevention
Select cultivars labeled resistant to the Fusarium races present in your region. Rotate away from susceptible hosts for five or more years when possible, using grasses or other non-hosts. Keep soil pH near neutral to slightly alkaline for many vegetable systems. Use clean transplants and disinfect tools and pots. Avoid moving soil from known infested beds on boots or equipment.
Management
Pull and destroy symptomatic plants; do not till them into the bed. Solarize soil under clear plastic in hot seasons where practical. Graft tomatoes and related crops onto resistant rootstocks for high-value plantings. Incorporate compost and encourage beneficial microbes such as Trichoderma where products are available, recognizing they support resilience more than cure. Raise beds and improve drainage so roots are less stressed. Replant with resistant varieties only.