WSU Extension


Armillaria root rot 
Botrytis shoot blight 
Gray blight 
Leaf spot 
Lime-induced chlorosis 
Marginal leaf necrosis 
Physiological leaf spot 
Phytophthora blight 
Phytophthora root rot 
Powdery mildew 
Ramorum leaf and shoot blight (Sudden oak death) 
Salt injury 
Tissue proliferation 
Azalea bark scale 
Lecanium scale 
Rhododendron lace bug 
Rhododendron whitefly 
Root weevils 

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Caption: Rhododendron tissue proliferation
Photo by: R.S. Byther
Rhododendron : Tissue proliferation
(revision date: 4/23/2014)

There is no known cause of tissue proliferation, but it is currently believed to be a genetic abnormality. A swollen area or gall develops at the base of the trunk or (more rarely) on a shoot. Otherwise, the plants appear to be healthy. Numerous small sprouts may develop from the swollen area, which may deteriorate after several years. Plants may break at the site of the swelling. Tissue proliferation is apparently noninfectious, and does not seem to be spread by grafting. Tissue proliferation is also occasionally observed on azaleas.
Management Options

Non-Chemical Management
  • Give plants proper cultural care to maintain good health.
  • Do not force into accelerated growth.
Select non-chemical management options as your first choice!

Chemical Management

None recommended


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Caption: Rhododendron tissue proliferation
Photo by: R.S. Byther