WSU Extension

Hortsense

Apple
 
Disease
Anthracnose and Bull's-eye rot 
Bitter pit 
Burrknot 
Crown and collar rot 
Crown gall 
Cytospora canker 
Fire blight 
Fruit russeting 
Nectria canker (European canker) 
Nectria twig blight (Coral spot) 
Perennial canker (Bull's-eye rot) 
Phytophthora fruit rot 
Powdery mildew 
Scab 
Virus diseases 
Insect
Aphids 
Apple ermine moth 
Apple maggot 
Apple-and-thorn skeletonizer 
Brown marmorated stink bug 
Codling moth 
Cutworms and armyworms 
Earwigs 
Fruittree leafroller 
Leafhoppers 
Leafrollers 
Lecanium scale 
San Jose scale 
Spider mites 
Tent caterpillars 
Tentiform leafminer 



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Caption: Fire blight infected fruit
Photo by: G.G. Grove
  
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