Phytophthora Canker and Shoot Blight
Phytophthora spp. (P
12 host plants
Last updated
This profile synthesizes data from multiple published sources. Expert field review is in progress.
You'll see cankers on stems and branches with associated shoot blight and dieback. Prune out infected branches well below visible symptoms and disinfect tools. Avoid wounding plants and keep them healthy to minimize infection. Improve drainage and reduce soil moisture stress. This pathogen favors cold, wet conditions. This blight is most damaging during cool, wet springs when flower and shoot development is rapid. Monitor plants closely during vulnerable periods.
Prevent mechanical injury to trees, especially late in the season. Avoid leaving plants on the ground during rainy winter weather.
Quick Reference
Management
P. syringae: winter and early spring (November-April) when cool and wet; P. cactorum: spring through fall (May-October) during warm, wet periods. In the Puget Sound region, canker development is most active during cool, wet fall/winter (September-February for P. syringae) and warm spring/summer (April-August for P. cactorum). # Source: PNW Plant Disease Management Handbook
Cool wet weather (especially fall/winter for P. syringae, warm wet for P. cactorum); rain splash; overhead irrigation; wounded tissue; susceptible cultivars; proximity to infected soil or mulch. # Source: PNW Plant Disease Management Handbook - Phytophthora Canker and Shoot Blight
Cultural Controls
- Prevent mechanical injury to trees, especially late in the season.
- Avoid leaving plants on the ground during rainy winter weather.
- Plant on well-drained sites.
- Avoid mounding soil around the trunks.
- Also, do not \"heel-in\" higher than the collar.
- Harvest highly susceptible nursery plants during dry weather.