ID black canker on red alder trunk

Asked July 11, 2019, 3:27 PM EDT

Hello I was wondering if you could help ID the canker(?) on this red alder. I find them regularly on trees in my area (Vancouver Island) and have never been able to positively Id them. Thank you.


1 Response

The pattern of staining matches up with damage caused by alder bark beetles, most likely Alniphagus aspericollis. Each spot marks a beetle entry, with the charactieristic dark stains produced by the sap bleeding from the entry hole.

Bark beetle attacks like this on red alder have been common over the last several years. I have seen these repeatedly while out measuring red alder study plots in Oregon and Washington. If you are able to cut and peel the bark off of one of the infested trees, you should be able to see the signs of beetle feeding and breeding chambers between bark and sapwood.

The increased incidence of alder bark beetles recently (~5 years) seems to be associated with summer heat and drought stress. Alder bark beetles typically attack injured or stressed trees. They also breed in fresh down wood from weather or from cutting and they can attack healthy green trees nearby.