WSU Extension

Hortsense

Caption: Fire blight infected fruit
Photo by: G.G. Grove
  
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Apple : Fire blight
(revision date: 7/13/2015)


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, appearing scorched. Cankers can develop on twigs and branches, sometimes girdling the limb and causing dieback. Bacterial ooze occurs on infected tissues during humid weather. Fire blight symptoms can sometimes be found around the graft union in apples. Water-soaked purplish cankers may occur near the base of the tree. Reddish-brown streaking beneath the bark in the cankered area may be observed. Some apple trees may collapse and die without showing any characteristic blight symptoms in the canopy. These deaths may be confused with other disease problems such as root rots. Fire blight is not a proven problem in western Washington.
Management Options

Non-Chemical Management
  • Plant resistant varieties such as 'Northern Spy', 'Red Delicious', and 'Stayman Winesap'. 'Liberty', 'Prima', and 'Redfree' are also resistant but are less commonly planted.
  • Avoid use of very susceptible rootstocks including M9, M26, M27, Mark, and Ottawa 3.
  • Prune out and destroy infected tissues as soon as they are noticed. Make cuts at least 6" below infected areas and sterilize pruning tools between cuts. Do not perform blight removal during regular pruning.
  • Provide proper culture to minimize succulent shoot growth and reduce injuries, including winter injury.
  • Avoid wounding plants.
Select non-chemical management options as your first choice!

Chemical Management


None recommended

Images
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Caption: Fire blight infected fruit
Photo by: G.G. Grove
Caption: Fire blight cankers
Photo by: G.G. Grove
Caption: Fire blight canker on trunk
Photo by: G.G. Grove
Caption: Fire blight strike on apple tree
Photo by: M. Bush