For better or for worse (mostly for worse), many diseases are named in part after pathogens. This was “annosus root disease” when the pathogen was called Fomes annosus. When the name Heterobasidion annosum came into common use, some felt the need to change the disease name to “annosum root disease”. When multiple species were carved out of H. annosum sensu lato, the feeling was to give up that approach and use the genus, or “Heterobasidion root disease(s)”. And how long will it be until a new genus is used for these species?
Obviously, this is very confusing to nonspecialists. In addition, it is completely unnecessary. These are not latin and common names of the same thing. One is a pathogen; one is a disease. There is no reason to change the disease name just because a new pathogen name is used.
But it does illustrate the awkwardness of incorporating pathogen names in disease names. I’m sure nonspecialists, like foresters and arborists, would appreciate more descriptive names that don’t incorporate seemingly meaningless latin.