WSU Extension

Hortsense

Pear
 
Disease
Crown gall 
European canker (Nectria canker) 
Fire blight 
Pacific Coast pear rust 
Pear trellis rust 
Powdery mildew 
Pseudomonas blossom blast and dieback 
Scab 
Stony pit 
Virus diseases 
Insect
Aphids 
Apple-and-thorn skeletonizer 
Brown marmorated stink bug 
Codling moth 
Cutworms and armyworms 
Pear psylla 
Pear slug (pear sawfly) 
Pearleaf blister mite 
San Jose scale 
Spider mites 



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Caption: Fire blight infected fruit
Photo by: G.G. Grove
  
Pear : Fire blight
(revision date: 5/19/2015)


Biology
Fire blight is a bacterial infection which typically attacks via wounds or blossoms. Initially, twigs and flowers appear water-soaked. Infected tissues quickly turn brown to black and die back, often bending over in a "shepherd's crook". Blighted tissues remain on the tree, giving it a scorched appearance. Dark, somewhat sunken cankers develop on twigs and branches, sometimes girdling the limb and causing dieback. A brownish bacterial ooze is common at the margins of cankers, especially during humid weather. Fruit may also be infected, showing sunken black spots up to 1" in diameter and 1/4" deep. The bacteria overwinter in infected tissues and can be transmitted by rain and pollinating insects. Fire blight is not a proven problem in western Washington. Pseudomonas blossom blast and dieback is caused by a different species of bacteria, but the symptoms may be similar.
Management Options

Non-Chemical Management
  • Plant resistant varieties when possible. 'Giant Seckel', 'Mac', 'Maxine', and 'Moonglow' are reported to be somewhat resistant.
  • Prune out and destroy infected tissues when noticed. Make cuts at least 6" below infected areas and sterilize pruning tools between cuts. To reduce chances of spreading bacteria, do not perform blight removal during regular pruning.
  • Provide proper culture to minimize amount of succulent shoot growth and to reduce injuries including winter injury.
  • Avoid wounding plants.
Select non-chemical management options as your first choice!

Chemical Management

Bactericidal sprays applied during the main bloom season are very effective. Do not apply copper products to 'Anjou', 'Comice' or 'Forelle' pears or severe russeting may occur. 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
  • Lilly Miller Kop-R-Spray Conc
    Active ingredient: metallic copper  |  EPA reg no: 909-92
  • 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: Fire blight infected fruit
Photo by: G.G. Grove
Caption: Pear fruit infected with fire blight
Photo by: G.G. Grove
Caption: Fire blight infected leaves
Photo by: T.J. Smith
Caption: Fire blight canker on trunk
Photo by: G.G. Grove
Caption: Pear fruit infected with fire blight
Photo by: E.M. Bentley