Phaeoacremonium fraxinopennsylvanicum

Phaeoacremonium fraxinopennsylvanicum is a pathogenic fungus known to cause vascular wilts and canker diseases in various woody plant species. It specifically targets the internal vascular tissues, disrupting the transpiration stream and metabolic processes, which leads to the progressive decline of the host tree’s health and vitality.

The primary host for this fungus is the green ash (Fraxinus pennsylvanica). The pathogen is often identified in stands where trees are under stress, making it a significant concern for forestry management and urban arboriculture, as it can cause widespread mortality if not monitored and managed effectively.

Visible symptoms often include the development of bark cankers, sunken lesions on the trunk and branches, and gradual dieback of the crown. Upon examination of the wood tissue, internal discoloration is usually present, representing the fungal colonization of the xylem and the tree’s defensive response to the invasive hyphae.

The disease cycle is primarily driven by spore dispersal via wind, splashing rain, and insect vectors. The fungus thrives in conditions of high humidity and is opportunistic, often gaining entry to the host plant through wounds caused by pruning, storms, or pest damage, making preventative care of tree injuries essential.

Management and prevention protocols focus on strict sanitation practices, including the removal and destruction of infected wood to reduce spore pressure. It is crucial to maintain tree vigor through proper irrigation and fertilization, while ensuring that pruning is done correctly and tools are sanitized to prevent cross-contamination between healthy and diseased plants.