WSU Extension

Hortsense

Caption: Azalea leaf and flower gall
Photo by: R.S. Byther
  
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Azalea : Leaf and flower gall
(revision date: 4/11/2018)


Biology
The leaf and flower gall fungus attacks expanding leaf and flower buds. Initially, the affected plant part shows a thickening and gradually assumes a fleshy appearance. Leaves may thicken into fleshy, bladder-shaped galls. The galls are pale green to pink and may later be covered with a white material. Eventually the leaf galls lose their green or pink color and become brown and hard. Parts of leaves or entire leaves may be affected. The disease is favored by high humidity and wet leaves. Damage is primarily aesthetic.
Management Options

Non-Chemical Management
  • Avoid overhead watering.
  • Space and prune plantings to provide good air circulation.
  • Plant varieties which are less susceptible to disease.
  • Prune and destroy galls before they turn white to reduce reinfection risks. Prune and destroy any old galls, also.
Select non-chemical management options as your first choice!

Chemical Management


Apply to entire plant before buds break in the spring. Repeat 2 to 3 weeks later.

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
  • Monterey Liqui-Cop Copper Fungicidal Garden Spray
    Active ingredient: copper-ammonia complex  |  EPA reg no: 54705-7
  • Soap-Shield Flowable Liquid Copper Fungicide [Organic]
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-56872
  • This list may not include all products registered for this use.
Images
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Caption: Azalea leaf and flower gall
Photo by: R.S. Byther
Caption: Azalea leaf and flower gall
Photo by: R.S. Byther
Caption: Rhododendron leaf gall
Photo by: R.S. Byther