Canker Diseases

Evan Ogden Senior Staff

Evan Ogden
Senior Staff

One of the most difficult and frustrating challenges to growing backyard tree fruit in our moist Northwest environment is the presence of canker diseases.

These maladies are a result of either a fungal infection or a bacterial infection and symptoms can range from blossom and twig dieback at the earlier stages to large, necrotic lesions or cankers on major scaffold branches and trunks. Both are spread by extended, splashing rainfall and wind, boring insects, as well as contaminated pruning tools.


The canker disease we encounter regularly on apple and pear trees in our area is a fungal     pathogen commonly called “European canker” (Nectria Gallegina). If you find a canker on an   apple tree in Thurston County, it is likely this. Sunken lesions form on new branches below     leaf scars and eventually spread down the branch, forming larger cankers with concentric      growth ridges evident. These cankers can eventually girdle branches, cutting off water and nutrient supply and causing death. More info here:

Another widespread canker disease that shows up in stone and pome fruits as well as a large host of other ornamental plant varieties in our area is Pseudomonas Syringae. Also known as “Fire Blight” on fruit trees. This is a bacterial pathogen that is responsible for several types of symptoms including blossom blast on cherries, shoot collapse on lilac, and of course, canker lesions on the branches of many varieties of fruit and ornamental trees and shrubs. As with European Canker, these expanding cankers can girdle and kill even large branches as well as entire trees. If you have seen cherry or plum trees exuding an amber colored, gummy sap, it is likely symptoms of a Pseudomonas infection. Pear limbs that look to have been scorched with a blow-torch are likely infected with Pseudomonas, thus the “Fire Blight” moniker. Read here for more in-depth information on Pseudomonas Syringae:

Lastly, another persistent and difficult to control canker disease common to our climes is several strains of Cytospora, also known as Perennial canker or Peach canker. This rain-spread pathogen is at work year round, whenever it rains, infecting weak and damaged trees through pruning wounds, frost damage, insect damage and bacterial infection sites. This pathogen also attacks spruce and fir trees in our area. The only beneficial treatment for Cytospora is maintaining healthy soil conditions, proper and minimal pruning, plant spacing that provides adequate air circulation; as well as correct irrigation practices. Cankered and dead limbs should be pruned out and destroyed to stop spores from reinfecting. This should be done in dry weather, disinfecting pruning tools in rubbing alcohol after each pruning cut. As of yet, there are no effective chemical treatments available for treatment of Cytospora.


On the bright side!

Both Pseudomonas Syringea and Nectria Gallegina can be treated with Copper Hydroxide at proper timing and intervals to mitigate the spread of disease. This, in concert with proper pruning techniques, destruction of infected plant material plus balanced fertilization, (our SuperRoots program) can allow every opportunity to extend the life of your beloved fruit and ornamental trees and shrubs.

Mid October is the optimal window for the first treatment of canker diseases. Feel free to give us a call if you are interested in allowing us to evaluate whether a canker disease treatment is warranted on your fruit or ornamental trees. We can also help you optimize the growing conditions of trees that aren’t infected yet!

Best Treegards,

Evan Ogden

Senior Staff

360 250 6346