Root and Stem Rot
Phytophthora syringae
2 host plants
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
Root and stem rot causes decay and wilting of affected plants. Improve drainage and avoid soil moisture stress. Remove infected plants. Rotate to new land if possible. Select resistant varieties for future plantings. Proper drainage and good site selection are critical to prevent root disease problems. Monitor plants for early signs of decline or wilting Early detection and prompt management of symptoms help limit disease spread.
Root rots thrive in waterlogged soil, so drainage is your most important intervention. Avoid overwatering and ensure the planting site drains well. Remove severely affected plants to prevent spread to neighbors through root contact or contaminated soil. When replanting, choose resistant species or improve soil structure before putting anything back in the ground.
Quick Reference
Management
Winter disease of nursery stock, especially on harvested trees stored in coolers or heeled-in outdoor sawdust beds (October–April in Pacific Northwest). Occurs primarily during cold, wet conditions when soil is near saturation. Young nursery plants more susceptible than established trees. # Source: PNW Handbook (crabapple-stem-rot)
Phytophthora syringae is a soilborne, cold-weather pathogen that grows and is active at lower temperatures than other Phytophthora species. Infection occurs through wounds caused by handling or pruning, or through leaves and leaf scars. The organism survives in soil and in fallen leaves. Zoospores move passively with rain splash, surface water, and water in soils near saturation. Rapid spread occurs during cold, rainy periods. # Source: PNW Handbook (crabapple-stem-rot)
Cultural Controls
- Prevent mechanical injury to trees, especially late in the season. Avoid leaving trees on the ground during rainy winter weather.
- Plant on well-drained sites. Avoid mounding soil around trunks. Do not 'heel-in' (store bare-root trees in sawdust piles) higher than the collar.
- Harvest susceptible nursery trees during dry weather, not during wet periods when disease pressure is high.
- Remove and destroy all infected plants and plant debris promptly.
- Minimize wounding during dormant season; prune only in dry conditions.
- Improve drainage in nursery beds and fields where trees are stored or grown.