Root and Crown Rot
Phytophthora cinnamomi
4 host plants
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
Root and crown rot from Phytophthora cinnamomi attacks at soil level and spreads into roots and lower stems, causing sudden wilting, yellowing foliage, and plant collapse even though the canopy may look healthy. Affected roots and crown tissue become soft and discolored. The disease progresses rapidly in waterlogged soil and warm conditions, killing plants over weeks to months. You may notice the problem appearing in localized areas of the landscape where water collects or drainage is poor.
This soil-borne pathogen thrives in wet, poorly drained conditions common in gardens after heavy rain. Excellent drainage is non-negotiable: ensure containers sit on gravel (4 inches or deeper) rather than directly on the ground, raise beds at least 15 inches, and break up compacted soil in planting areas. Avoid reusing pots or soil from previous crops without sterilization. Plant only certified disease-free nursery stock, and select resistant cultivars when available. Once established in a site, the pathogen is difficult to eliminate, so the priority is preventing it through cultural practices.
Quick Reference
Management
Cultural Controls
- Provide good drainage: the most critical control measure. Place containers on gravel beds (4 inches or more deep) to allow drainage. Do not place containers on poly sheets—they prevent containers from draining into soil and allow contaminated drainage water to spread from the base of one container to another.
- Avoid reusing pots from a previous crop. If pots must be reused, wash off all debris and soak in a sanitizing solution or treat with aerated steam for 30 minutes.
- Use disease-free plants and inspect incoming nursery stock; discard any showing root rot symptoms.
- Amend soils with composted bark mulch (not fresh sawdust) to provide good aeration for roots. Plant in raised beds with top at least 12 inches above surrounding soil.
- Manage irrigation carefully: do not overwater or create saturated conditions lasting 48+ hours. Bury drip lines 1 foot away from plant base. Allow soil to dry between irrigations.
- Avoid excessive nitrogen fertilization; higher phosphorus and potassium appear to stimulate root production and improve plant resistance.