WSU Extension

Hortsense

Viburnum
 
Disease
Bacterial blight (Leaf spot) 
Leaf spot 
Powdery mildew 
Ramorum leaf and shoot blight (Sudden oak death) 
Shoot blight (Gray mold) 
Insect
Bean aphids 
Root weevils 
Viburnum leaf beetle 



print version| pdf version| email url    
Caption: Viburnum bacterial blight (leaf spot)
Photo by: R.S. Byther
  
Viburnum : Bacterial blight (Leaf spot)
(revision date: 5/19/2015)


Biology
Bacterial blight of viburnum primarily affects leaves and occasionally stems. Spots on leaves first appear as brown, watersoaked areas which may be round, irregular, or angular in outline. Developing leaves may become deformed if heavily infected. Spots on stems may be more elongate and less noticeable than the leaf lesions and may also become sunken. Lesions on both stems and leaves may give off a bacterial ooze or exudate near the margins. Severe infections may also result in shoot dieback. Bacterial blight is favored by cool, moist conditions. The bacteria can infect through wounds and are easily spread by splashing water and pruning tools.
Management Options


Non-Chemical Management
  • Plant resistant viburnums such as Viburnum burkwoodii 'Mohawk', V. carlcephalum 'Cayuga', V. lantana 'Mohican', or V. rhytidophyllum 'Alleghany'.
  • Plant in full sun.
  • Space plants and prune to provide good air circulation.
  • Remove and destroy infected leaves and shoots in dry weather. Sterilize pruning tools between cuts.
  • Rake and destroy fallen leaves.
  • Avoid wounding plants, especially during conditions favoring infection.
Select non-chemical management options as your first choice!

Chemical Management

Apply fungicides in September and again before fall rains. An additional application may be made as new growth emerges in the spring. Homeowners should not make foliar applications to trees over 10 ft tall. Consult a commercial pesticide applicator for treatment of trees and shrubs over 10 ft. tall.

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 Liquid Copper Fungicide Conc/Organic Gardening
    Active ingredient: copper octanoate  |  EPA reg no: 67702-2-4
  • Monterey Liqui-Cop Copper Fungicidal Garden Spray
    Active ingredient: copper-ammonia complex  |  EPA reg no: 54705-7
  • This list may not include all products registered for this use.
Images

+ Show larger images

 
Caption: Viburnum bacterial blight (leaf spot)
Photo by: R.S. Byther