Sooty-Bark Disease of Maple

Chris Rippey Chris Rippey
Rippey Arboriculture, LLC
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In February and March of 2020, samples taken for DNA Sequencing from a declining Sycamore maple (Acer pseudoplatanus) and red maple (Acer rubrum) in Seattle, Washington came back positive for Cryptostroma corticale, also known as Sooty-Bark Disease. This is the first time this disease has been found in red maple. 

Sooty Bark Disease attacks and kills the cambium and bark of infected trees resulting in canopy decline and eventually death. This pathogen is from northeastern America where it does not cause disease. It was introduced to Europe where it has caused a disease in field maple (A. campestre), Norway maple (A. platanoides) and box elder (A. negundo). 

Signs of this disease include twig or branch dieback, brownish necrosis with green margins in the cross section of infected trees and shedding of bark to reveal brown-black fungal masses. Like many fungal infections, the incidence of this disease is expected to increase with higher temperatures and drought conditions.

Most importantly, the fungal spores of C. corticle are hyper-allergenic and can cause what is known as  hypersensitivity pneumonitis, a disease found among paper mill workers who dubbed it “Maple Bark Stripper’s Disease”. Recommendations have been made in Europe to protect both people and trees from infection, such as keeping the public away when working on infected trees, performing work in wet weather to minimize spore spread, not using the wood of infected trees for firewood, covering loads while in transit, and burning debris from infected trees.

Please consult with your company’s safety representative to develop work protocols related to this disease and to determine requirements for Personal Protection Equipment.