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 rust
Photo by: R.S. Byther
  
Rhododendron : Rust
(revision date: 4/23/2014)


Biology
Yellowish spots on the upper leaf surface and dark brown or purple spot on the lower leaf surface can indicate the presence of a rust infection. Later, the underside develops blisters which break open to reveal characteristic yellow to orange or reddish spores. Rusts can also affect azaleas. The disease overwinters on the host plant.
Management Options


Non-Chemical Management
  • Prune and destroy infected leaves.
  • Clean up and destroy any diseased leaves that have fallen to the ground.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Rhododendron rust
Photo by: R.S. Byther