Twig Dieback
Phacidiopycnis washingtonensis
2 host plants · Fungal
Last updated
This profile contains verified disease data from extension databases. Regional field notes and expert review are in progress.
Madrone (Arbutus menziesii) twigs become discolored and die from Phacidiopycnis washingtonensis infection. Remove cankers, dead twigs, and mummified fruit. Avoid overhead irrigation and limit over-tree cooling to reduce tree wetness duration. No chemical controls are available; cultural management is your only option.
Remove affected material as you find it and clean up any fallen debris where twig dieback spores can overwinter. Improve air circulation around susceptible plants through selective pruning. Avoid overhead irrigation during vulnerable growth periods. If the problem is persistent, your local Extension office can recommend current fungicide or bactericide options for your specific situation.
Quick Reference
Management
Peak activity Oct–May during cool, wet period. Twig death and dieback visible winter/spring. Symptoms develop Mar–June. BBCH 97–09.
Cool, wet dormancy favors fungal activity. High humidity and prolonged moisture. Sporocadus active during cool season. Wound entry opportunistic.
Cultural Controls
- Remove and destroy cankers, dead twigs, and mummified fruit. Avoid overhead irrigation. Limit over-tree cooling to keep trees wet for shorter periods of time.