Cryphonectria parasitica is a fungal pathogen known for causing chestnut blight, a disease that severely affects American chestnut trees. This fungus invades the bark of the tree, leading to cankers that disrupt the tree's ability to transport nutrients and water, ultimately resulting in tree death. Originally from Asia, Cryphonectria parasitica was introduced to North America in the early 1900s, leading to the rapid decline of the native chestnut population. Efforts to control the spread of this pathogen include breeding resistant tree varieties and exploring biological control methods to restore the chestnut ecosystem.