Response follow up to # 673760
I had trouble responding to the original question
The fungus is only on the trunk. It now looks powdery and light brown. Before, it was pure white, and very hard to the touch. About 1/2 inch thick.
Ramsey County Minnesota
I am sorry a diagnosis can’t be made from a photo. A sample can be sent to the plant disease clinic and they can identify it. Fungal identifications to be accurate require a laboratory.