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: Botrytis shoot blight
Photo by: R.S. Byther
  
Azalea : Botrytis petal blight
(revision date: 4/11/2018)


Biology
Botrytis petal blight is a fungal disease typically found in early spring. Symptoms of infection include brown, water-soaked spots on the leaves, and masses of gray-brown spores which form on infected tissues. Botrytis petal blight often occurs after the plant is injured or stressed.
Management Options


Non-Chemical Management
  • Good air circulation is essential. Space plantings to reduce humidity and allow good air flow.
  • Avoid overhead watering.
  • Prune out infected tissue, making cuts into healthy wood and disinfecting pruning tools between cuts.
  • Clean up and destroy any diseased material beneath plants.
  • Remove faded flowers and yellow leaves from plants.
Select non-chemical management options as your first choice!

Chemical Management

Application interval varies by label. Best when used with cultural controls. Copper and chlorothalonil products may discolor blooms.

Listed below are examples of pesticides that are legal in Washington. Always read and follow all label directions.
  • Bonide Copper Fungicide Spray or Dust RTU [Organic]
    Active ingredient: basic copper sulfate  |  EPA reg no: 4-58
  • Bonide Fung-onil Multi-Purpose Fungicide Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 60063-9-4
  • Captan 50% WP Fruit & Ornamental
    Active ingredient: captan  |  EPA reg no: 4-459
  • GardenTech Daconil Fungicide Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 67572-82-71004
  • Ortho Max Garden Disease Control Conc
    Active ingredient: chlorothalonil  |  EPA reg no: 239-2522
  • Spectracide IMMUNOX Multi-Purpose Fungicide Spray Conc
    Active ingredient: myclobutanil  |  EPA reg no: 9688-123-8845
  • This list may not include all products registered for this use.
Images

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Caption: Botrytis shoot blight
Photo by: R.S. Byther