Fusarium crown and root rot identification & organic treatment
Fusarium oxysporum f. sp. radicis-lycopersici (and related formae)
How to identify fusarium crown and root rot
A close relative of Fusarium wilt that attacks the crown and root system rather than moving up the whole vascular system, causing a brown, sunken canker right at the soil line.
Symptoms
- Brown, dry canker girdling the stem at or just above the soil line
- Wilting of the whole plant, often appearing suddenly once the canker girdles the crown
- Cutting the stem near the soil line shows internal browning limited to the lower few inches (unlike full wilt disease which runs higher up the stem)
- Roots may show brown rot alongside the crown lesion
Host crops
Tomato, Cucumber, Watermelon.
How it spreads
Soilborne and seedborne; survives for years in soil debris, spreads via contaminated soil, water, and equipment.
Favorable conditions
Cool soil temperatures (60-68°F) at planting followed by stress; high plant density and continuous cropping increase pressure.
Progression
- Root/crown infection (At or soon after transplant, cool soil) — Silent early colonization.
- Canker development (Weeks later) — Brown lesion girdles the stem base.
- Wilt and collapse (Once girdling is severe) — Sudden whole-plant wilt despite normal soil moisture.
Organic treatment for fusarium crown and root rot
- 1. Remove and destroy affected plants · medium effort
Pull the plant and surrounding root zone soil where feasible; discard away from the compost pile.
When: At diagnosis
- 2. Graft onto resistant rootstock · high effort
For high-value tomato plantings, grafting onto resistant rootstock sidesteps the pathogen at the roots.
When: At transplant stage
- 3. Solarize soil · medium effort
Clear plastic over moist soil for several hot summer weeks reduces surface inoculum between crops.
When: Fallow period
Prevention
- Rotate out of tomato/cucurbit ground for 4+ years.
- Use pathogen-free potting mix for starts; avoid reusing garden soil in trays.
- Avoid planting into cold soil; warm beds with clear or black plastic before transplanting.
Easy to confuse with
Fusarium wilt (vascular streaking higher up the stem), Southern blight (white mycelial mat, sclerotia present).