Possible biscogniauxia canker on Maple - Ask Extension
Hello!
My friend has a Maple in her front yard that has a 10" diameter trunk and is about 25ft tall. The bark has been sloughing off to reveal...
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Possible biscogniauxia canker on Maple #926697
Asked March 24, 2026, 11:21 PM EDT
Hello!
My friend has a Maple in her front yard that has a 10" diameter trunk and is about 25ft tall. The bark has been sloughing off to reveal a powdery white layer with some fungal hyphae in some sections. The leaves yellowed and dropped before fall last year and she said she did not water it during the summer.
It has affected most main branches in patches and starts at about 3 feet on the main trunk.
I believe it is biscogniauxia (hypoxylon) and needs to be removed.
Could you please help me identify this problem?
Thank you for your help!
Multnomah County Oregon
Expert Response
Thank you for your question, Ryan. Some maple (Acer) species are more susceptible to one fungal infection than another. I do not know what species this tree is.
Although canker diseases are found in PNW acer species, biscogniauxia (hypoxylon) is not one identified by the OSU Plant Clinic. I do not see any bleeding from the cankers, but perhaps that is just the angle.
The most probable cause of these cankers is
Phytophthora cactorum (https://pnwhandbooks.org/plantdisease/host-disease/maple-acer-spp-bleeding-canker)
I would suggest that your neighbor send samples of the tissue to the OSU Plant Clinic for diagnosis. https://bpp.oregonstate.edu/plant-clinic/submit-sample/how-submit-plant-materials
The disease probably is not curable, but an effective fungicide might slow the disease. Good luck!
Although canker diseases are found in PNW acer species, biscogniauxia (hypoxylon) is not one identified by the OSU Plant Clinic. I do not see any bleeding from the cankers, but perhaps that is just the angle.
The most probable cause of these cankers is
Phytophthora cactorum (https://pnwhandbooks.org/plantdisease/host-disease/maple-acer-spp-bleeding-canker)
I would suggest that your neighbor send samples of the tissue to the OSU Plant Clinic for diagnosis. https://bpp.oregonstate.edu/plant-clinic/submit-sample/how-submit-plant-materials
The disease probably is not curable, but an effective fungicide might slow the disease. Good luck!
