The butternut tree is being killed throughout its range by a canker caused by the fungus Sirococcus clavigignenti-juglandacearum, butternut canker disease, described as a new species in 1979. Although there are no reports of this fungus outside of North America, it is thought to be an exotic pathogen.
The Northern Research Station is identifying trees with possible resistance, propagating, preserving and testing them further.
They are also investigating genetic markers that may be linked to resistance, to help identify more resistant trees.
See Saving the Butternut.