WSU Extension

Hortsense

Azalea
 
Disease
Botrytis petal blight 
Cylindrocladium blight & root rot 
Leaf and flower gall 
Leaf spot 
Lime-induced chlorosis 
Marginal leaf necrosis 
Nematode (stunt) 
Ovulinia petal blight 
Powdery mildew 
Root rot (Phytophthora) 
Insect
Azalea bark scale 
Azalea lace bug 
Azalea leafminer 
Obliquebanded leafroller 
Root weevils 
Spider mites 



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Caption: Phytophthora root rot infecting trunk
Photo by: R.S. Byther
  
Azalea : Root rot (Phytophthora)
(revision date: 4/23/2014)


Biology
The symptoms produced by Phytophthora root rot are often confused with those caused by environmental or cultural problems. Above ground, infected plants may show stunting, yellowish-green leaves, branch dieback, wilt, and even plant death. Dead leaves persist on the branches instead of dropping. Underground, the roots rot, progressing from the smallest to the largest. The fungus may also cause rot in the main stem. Phytophthora persists in the soil and can infect new plants placed in the same area. Diseased plant tissues and debris are other sources of infection.
Management Options


Non-Chemical Management
  • Choose the right plant for the location and provide good cultural care. A healthy plant is more resistant to disease.
  • Plant only disease-free materials.
  • Remove and destroy all infected plants to prevent spread of the disease.
  • Select resistant azalea species such as R. poukhanense or resistant cultivars such as 'Formosa', 'Fakir', 'Corrine Murrah', 'Merlin', or 'Hampton Beauty' for planting in infected areas.
Select non-chemical management options as your first choice!

Chemical Management

None recommended

Images

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Caption: Phytophthora root rot infecting trunk
Photo by: R.S. Byther