Sirococcus clavigignenti-juglandacearum is a mitosporic fungus that causes a lethal canker disease of Butternut trees (Juglans cinerea). Known in the vernacular as butternut canker, it is also known to parasitize other members of the Juglans genus on occasion, and very rarely other related trees including hickories. The fungus is found throughout North America, occurring on up to 91% of butternut trees, and may be threatening the viability of butternut as a species.