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: Salt damage
Photo by: R.S. Byther
  
Rhododendron : Salt injury
(revision date: 4/23/2014)


Biology
Salt injury to rhododendrons is typically a result of culture or environment. Excessive salt (mineral) levels in the soil or irrigation water, excessive use of chemical fertilizers, or lack of water can be at fault. Edges of older leaves "burn" or become brown and dry and the plant may lose its healthy green color.
Management Options


Non-Chemical Management
  • Provide adequate irrigation.
  • Mulch around plants to prevent evaporation that can concentrate minerals in the root zone.
  • Improve drainage with addition of organic matter or by using raised beds.
  • Leach away excess salts by occasional heavy irrigation.
  • Decrease use of inorganic fertilizers.
  • Water potted plants from top only, and discard water that drains through.
  • Have suspect water supplies tested to determine salt content.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Salt damage
Photo by: R.S. Byther