Atropellis canker

Causal agent and disease type
Atropellis canker of pine is caused by the ascomycete fungus Atropellis piniphila. It is a serious infectious disease affecting the trunks and branches of various pine species. The pathogen attacks the bark and cambium, causing localized necrotic lesions that eventually lead to the structural weakening of the tree and long-term decline.

Susceptible hosts
The primary hosts of this fungus are various species of pine, with lodgepole pine (Pinus contorta) and western white pine being particularly susceptible. The disease is most common in forest stands and plantations located in regions with cool, humid climates that favor fungal growth and spore production.

Symptoms and signs
The most characteristic sign of the disease is the development of sunken cankers on the main stems or branches. These areas often exhibit heavy resin flow, which may harden into large, sticky masses. Underneath the affected bark, the wood is stained with a deep blue-black or brown discoloration, and small, dark fruiting bodies (apothecia) of the fungus can often be seen erupting through the bark surface.

Development and spread
The disease spreads primarily through spores dispersed by wind and rain splash. These spores infect trees through small wounds, cracks in the bark, or broken twigs. Once established, the fungus grows slowly into the inner bark and sapwood. The disease often persists for years, as the tree attempts to wall off the infection, resulting in deformed and gnarled stems.

Impact and control measures
The primary impact of Atropellis canker is the reduction of timber quality, stem deformation, and increased susceptibility to secondary pests or wind breakage. Management strategies include:

• Removing infected trees through sanitary thinning to reduce inoculum levels.
• Disposing of slash and logging debris to limit pathogen buildup.
• Selecting resistant or less susceptible pine species for reforestation efforts.
• Regular forest health monitoring and removal of heavily cankered stems during harvesting operations.