Nectria Canker (European Canker)
Neonectria ditissima
17 host plants
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
Apple or pear develops elliptical, sunken cankers on year-old twigs around leaf scars, with concentric callus rings forming yearly. Neonectria ditissima enters via fall rain and leaf scars in coastal high-rainfall areas. Cut out cankers during dry weather and disinfect tools. Choose less susceptible cultivars like Golden Delicious.
Prune out cankered branches at least six inches below visible symptoms, making cuts into healthy wood. Sterilize your tools between cuts. Canker pathogens typically enter through wounds, so minimize pruning injuries and avoid working on trees when bark is wet. Maintain tree vigor through proper watering and avoid stress from drought or compacted soil, which makes trees more susceptible.
Quick Reference
Management
Peak vulnerability during fall leaf drop and dormancy through early spring (September–May in Pacific Northwest), when cool, wet conditions favor infection. Leaf-scar infection window during abscission (September–November in Puget Sound). Post-infection canker expansion occurs during dormancy and early spring (Oct–May) when tree cannot effectively compartmentalize wounds. Avoid pruning during wet periods (late summer–fall); prune only during dry weather in late dormancy (Feb–Mar) when rapid callus formation begins. BBCH 97–09 (dormancy through bud break); do NOT prune during BBCH 10–79 (bud development through fruit development) in wet conditions.
Cool, wet conditions with high humidity and frequent rainfall (fall, winter, spring). Ascospore release requires moisture and occurs during rain events Sept–May. Peak infection risk occurs when rainfall exceeds 30% of days in a month AND temperatures average 52–60°F for ≥8 hours per day. This combination is common in Pacific Northwest maritime conditions Oct–April. Leaf-scar infection is most significant in fall (leaf drop); wound entry can occur year-round but is most successful during cool, wet periods when callus formation is slow. Frost cracks, pruning wounds, and branch breakage during dormancy create infection opportunities. Susceptible cultivars (Braeburn, Gala, Gravenstein, King, Macoun, McIntosh, Red Delicious, Spartan) are at higher risk than less-susceptible varieties (Golden Delicious, Honeycrisp, Jonagold, Jonathan, Northern Spy, Rome Beauty).
Cultural Controls
- Cut out and destroy cankers during dry weather.
- Disinfect pruning shears during wet weather.