WSU Extension


Armillaria root rot 
Collar rot 
Leaf scorch and leaf roll 
Powdery mildew 
Brown soft scale 
Lecanium scale 
Oystershell scale 

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Caption: Dogwood Phytophthora collar rot
Photo by: R.S. Byther
Dogwood : Collar rot
(revision date: 4/28/2014)

Collar rot is caused by a soilborne fungus which usually infects the plant through wounds on the trunk. It can also infect roots. A canker develops on the trunk near the soil surface or on the roots just below ground. This later becomes sunken and the bark falls off. The tree dies if the trunk is girdled. The first symptom of infection is general poor health, followed by death of twigs and branches. The same fungus causes root or collar rots in several different plant species.
Management Options

Non-Chemical Management
  • Prevent wounds on the tree trunk where the fungus can enter.
  • Remove and destroy infected trees, including large roots.
  • Do not replant in infected soils.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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Caption: Dogwood Phytophthora collar rot
Photo by: R.S. Byther