Thelonectria viridispora

Thelonectria viridispora is a fungal pathogen that belongs to the Ascomycota division, known for causing necrotic cankers on the bark of various hardwood trees. This fungus acts as a wound parasite, exploiting damaged areas on tree trunks and branches to colonize the cambium and disrupt the flow of nutrients within the plant.

Host plants typically include a range of deciduous species such as apple trees, pears, and beeches. The fungus is particularly dangerous in orchards and forest environments where environmental stress or mechanical damage creates entry points for the pathogen's spores to germinate and establish an infection cycle.

Symptoms of the disease are characterized by sunken necrotic areas on the bark, which may eventually crack and reveal the underlying wood. As the infection progresses, the pathogen develops fruit bodies (perithecia) that often exhibit a greenish hue. Severe cases result in girdling cankers that eventually lead to dieback of distal branches or the death of the entire tree.

The development and spread of Thelonectria viridispora are strongly linked to high moisture levels and mild temperatures. Spores are easily disseminated by wind and splashing rainwater. Furthermore, human activities such as improper pruning without tool sterilization are primary factors in moving the fungus from infected to healthy trees.

Effective management requires an integrated approach. Primary strategies include pruning out and destroying diseased wood, ensuring that all pruning wounds are protected, and maintaining overall tree vigor through proper fertilization. Chemical control involves the application of copper-based fungicides during the dormant season to suppress fungal populations and prevent new infections.