Sooty Bark Disease: What Lane County Maple Owners Should Know
A new threat to Northwest maples
Sooty bark disease is a fungal disease that kills maples, and it has reached Oregon. It is caused by the fungus Cryptostroma corticale. The fungus can live quietly inside a healthy tree for years. Then drought and heat stress weaken the tree, and the fungus turns aggressive.
Europe has battled outbreaks after hot summers for decades. Here in the Pacific Northwest, the disease was confirmed around Seattle in 2017 and has since been found in Portland and Bend. With our summers running longer and drier, Lane County property owners should know what to watch for.
Which trees are at risk
Sycamore maple is the most common host, but the fungus has been confirmed on several trees common in our area:
Bigleaf maple, our native maple
Vine maple
Norway maple
Red maple and Freeman maple
Japanese maple
Horse chestnut
Pacific dogwood
Stressed trees are the most vulnerable. That includes trees in tight urban spaces, along streets, or on dry, compacted sites.
Signs to look for
The name comes from the black, soot-like spore mats that appear once the outer bark falls away. Watch for:
Blistered or bulging bark on the trunk or major limbs
Patches where bark has peeled off, exposing dark gray to black powdery mats
Wilting leaves and dieback in the crown
Dark staining in the wood, often only visible once a tree is cut
Other problems can look similar. Brittle cinder fungus (Kretzschmaria deusta), for example, also produces dark crusts on bigleaf maple. Only a lab test can confirm sooty bark disease.
Why this isn't a DIY job
The spores are a health hazard. Breathing in large amounts can cause maple bark disease, a lung inflammation known as hypersensitivity pneumonitis. Symptoms can include cough, shortness of breath, fever, and fatigue.
The risk is low from walking past an infected tree. It rises sharply when the tree is cut, split, or chipped, because that work throws clouds of spores into the air. If you suspect an infected tree, don't cut it, stack it as firewood, or run it through a chipper yourself.
How Wolfpack Tree Care handles it
There is no cure once a tree is heavily infected, so the goal is accurate diagnosis and safe removal. Our process:
Assess. An ISA Certified Arborist inspects the tree and rules out look-alikes.
Confirm. We collect samples for lab testing when the signs point to sooty bark disease.
Protect the crew. We use respirators, disposable coveralls, and wet down bark before cutting.
Contain the debris. Infected wood is not chipped dry on site. It is covered for transport and disposed of properly.
Plan ahead. We help you choose resilient replacement trees and keep remaining maples healthy with proper watering and care.
All work follows ANSI A300 and ANSI Z133 standards.
Worried about a maple on your property?
If you see peeling bark, black powdery patches, or sudden dieback on a maple, call us before anyone cuts it. Wolfpack Tree Care serves Lane County and surrounding areas with hazard assessments and technical removals.
Wolfpack Tree Care · ISA Certified Arborist · CCB #228962 Call 541-556-9256 to schedule an assessment.
