Cytospora Canker is caused by a group of pathogens (Cytospora, Leucostoma and Valsa spp.) that infect both evergreen and deciduous woody plants, including pine, spruce, larch, fir, cherry, maple, poplar and willow. These pathogens have several spore stages so early detection and pruning is important to control this disease. Several years of infection can eventually kill the plant.

What to look for:

  1. Conspicuous dead branches on an otherwise healthy looking tree. On evergreens this starts on older lower branches and moves up the tree.
  2. Sunken areas of bark on affected branches.
  3. Small raised pimple like bumps on the bark: black, white, gray or pink in colour.
  4. Oozing milky orange to brown sap from canker sites, particularly during rainy weather.

What can you do?

  1. Keep your landscape plants healthy. Trees stressed by drought, construction damage, wounding or frost damage are often colonized by Cytospora.
  2. Prune out dead branches early to reduce the spread of the disease by spores. Prune the branch back to a lateral branch at least 30 cm (12”) away from any visible canker.
  3. Avoid pruning on rainy days. The risk of spreading pathogens is much higher on rainy days than on dry days.
  4. Sterilize your pruning tools between all cuts with one of these disinfectants:
    • Undiluted Listerine or Pine-sol
    • 10% solution of TSP (trisodium phosphate) - available in hardware stores
    • Alcohol dips + flaming (to burn off the alcohol and kill pathogens)


Tree infected with Cytospora Canker