What is it?
Hypoxylon canker is a fungus that occurs mostly on trembling aspen, also on other poplars and various hybrid poplars like balsam poplar, columnar aspen. It causes trunk cankers, which can eventually girdle and kill the tree.
Symptoms
- Infected leaves are smaller than normal, dead leaves often remain attached to branches.
- First sign are yellow to orange, slightly sunken area of bark compared to healthy, young, green-grey bark.
- Old cankers have yellow-orange edges. Their centers develop a blotchy, salt-and-pepper appearance as bark blisters and peels away in small patches. Wood beneath often is decayed and may contain wood-boring insects.
Damages
- Infected trees often break at the initial infection point due to wood decay, even if they look green.
- Canker can spread through wind-borne ascospores, which are released year-round.
- Cankers expand rapidly along the branches and trunks, and can kill the tree within few years.
What to do?
- No chemical treatment is effective.
- Avoid planting disease-susceptible trees. Encourage tree diversity by planting different tree species that are resistant to various pests and diseases.
- Prune dead/dying branches before canker reaches the main trunk.
- Remove severely infested trees to prevent damage.
Other resource:
https://tidcf.nrcan.gc.ca/en/diseases-caused-by-pathogens/factsheet/15