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 marginal leaf necrosis
Photo by: R.S. Byther
  
Rhododendron : Marginal leaf necrosis
(revision date: 4/23/2014)


Biology
Leaf scorch on rhododendrons is a response to stress. Symptoms include browning of tips or margins of leaves, with the damage sometimes spreading to the center of the leaf. Water stress (too much or too little), root or stem damage, high soil pH, and exposure to drying winds are some of the possible causes of leaf scorch.
Management Options


Non-Chemical Management
  • Know and follow the cultural requirements for your plant, including proper irrigation and fertilization.
  • Correct alkaline soil pH by adding organic matter or sulfur to make it more acidic.
  • Provide adequate soil moisture by irrigation where dry soil is a problem. If boggy conditions are at fault, it may be necessary to relocate the plant or use raised beds.
  • Shelter susceptible plants from drying winds, either with other plantings or by planting near structures.
  • The south/southwest side of the plant is the most likely to be damaged by direct sunlight, but plantings may also be damaged by reflected sunlight.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Rhododendron marginal leaf necrosis
Photo by: R.S. Byther