Cryphonectaria parasitica is a fungal pathogen known for causing chestnut blight, a disease that severely affects American chestnut trees. This fungus invades the tree's bark, leading to cankers that disrupt the flow of nutrients and water, ultimately resulting in the tree's death. Originally from Asia, Cryphonectaria parasitica was introduced to North America in the early 1900s. The rapid spread of this pathogen devastated the once-abundant American chestnut population, transforming it from a dominant species in eastern forests to a rare tree, significantly impacting the ecosystem and local wildlife.