WSU Extension

Hortsense

Rhododendron
 
Disease
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) 
Rust 
Salt injury 
Sunburn 
Tissue proliferation 
Insect
Aphids 
Azalea bark scale 
Caterpillars 
Lecanium scale 
Rhododendron lace bug 
Rhododendron whitefly 
Root weevils 



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Caption: Rhododendron gray blight
Photo by: R.S. Byther
  
Rhododendron : Gray blight
(revision date: 4/23/2014)


Biology
Gray blight is a fungal infection of the leaves. It usually becomes established after an injury to the leaf, such as sunscald, frost damage, or some mechanical injury. White spots or blotches with dark margins can be found on the leaf surface. On cut leaves, the infection may spread from the edge of the wound into the leaf tissue.
Management Options


Non-Chemical Management
  • Place plants to reduce injury from sunscald, frost, etc.
  • Infection spreads quickly between cuttings. Do not propagate diseased plants.
  • Prune diseased plants last. Disinfect tools often to avoid infecting healthy plants.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Rhododendron gray blight
Photo by: R.S. Byther