Poplar stem canker

Poplar stem canker is a serious fungal disease caused by the ascomycete fungus Plagiostoma populinum. It is categorized as a necrotic disease that affects the bark and vascular tissues of poplar trees, often leading to significant damage in both forest stands and ornamental plantings.

The disease primarily targets various species of the Populus genus, including trembling aspen. The pathogen invades the tree through wounds, such as frost cracks, pruning cuts, or insect feeding injuries. Once the fungus enters the cambium layer, it begins to colonize the living tissues, leading to localized necrotic lesions.

Symptoms of the disease are characterized by sunken or swollen areas of bark that eventually crack open, forming distinct cankers. As the fungus spreads, the tissue around the lesion dies, and the structural integrity of the stem or branch is compromised. In late summer or autumn, minute black fruit bodies appear on the surface of the infected bark, serving as a source of further inoculum.

The development of poplar stem canker is heavily dependent on environmental conditions, particularly high humidity and moderate temperatures. Spores are disseminated via wind and splashing rain, allowing the disease to spread rapidly through stands. Dense, poorly managed plantations provide the ideal microclimate for the pathogen to thrive and establish.

The pathogenicity of this fungus leads to reduced tree vigor, wood quality deterioration, and, in severe cases, the death of the tree due to girdling. Effective management involves sanitary pruning of infected branches, the use of resistant clones, and maintaining optimal tree spacing to improve air circulation and reduce the overall infection pressure in the landscape.