Overview
Phytophthora root and crown rot is caused by moisture-favoring oomycete pathogens. Poor drainage, saturated potting mix, and contaminated irrigation water greatly increase risk. It can rapidly decline valuable foliage and flowering container plants and requires stronger sanitation and isolation measures than simple overwatering.
How to identify it
Plants continue wilting despite moist mix; roots turn brown or black, soft, and easily shed their outer tissue. The crown or stem base develops water-soaked browning, foliage yellows and drops, and severe cases collapse rapidly.
Early signs and progression
Lower leaves yellow unexpectedly without dry mix, while the pot stays wet and roots begin browning; a dark, moist lesion may appear at the crown near the media line.
The disease can rapidly invade remaining healthy roots and the crown in wet mix and can move via contaminated mix, containers, tools, or drainage water. Plants with severe crown rot have a poor prognosis.
Prevention
Use clean, freely draining mix and sanitized containers; prevent standing water and shared drainage between pots; quarantine new plants; disinfect tools contacting diseased roots; manage watering to avoid prolonged saturation.
Lower-risk treatment
Immediately isolate the plant and prevent drainage from reaching other pots. Mild root infection may be managed by removing all soft rotten roots and contaminated mix, sanitizing tools, and repotting in clean mix; plants with extensive soft crown rot are generally best discarded.
Treatment steps
- Isolate a wilting plant in wet mix and keep its drainage away from other pots.
- Unpot and inspect roots, crown, and stem base to determine the extent of soft rot.
- For mild cases, trim rotten roots, discard old mix, and sanitize tools and the container.
- Repot in fresh freely draining mix and carefully regulate watering.
- Seal and discard plants with extensive crown rot or continued decline, and monitor neighboring containers.
Chemical treatment and safety
Professional production settings may use products labeled for Phytophthora disease, but home users should use only locally registered products explicitly labeled for the plant and disease, recognizing that chemicals cannot restore extensively rotted tissue.
Home remedies
- Root rescue for mild cases — Unpot mildly affected plants, trim all black soft roots, and repot in clean mix; disinfect tools before touching healthy tissue.
- Drainage isolation — Collect and discard drainage from affected plants separately so it cannot enter other pots or a shared tray.
Referenced products
- Clean free-draining potting mix — Use for repotting after diseased roots are removed; never reuse infected mix.
- Tool and container sanitizer — Use according to the label after handling affected plants.