The primary hosts of the rust fungus Melampsorella symphyti are various members of the Boraginaceae including Common Comfrey and Russian Comfrey.  The underside may be completely covered with the yellow-orange uredinia.  The telia are formed in the lower epidermis.

The alternate aecial host is the Silver-fir, Abies.   It is not considered to be a gall causer on either host.

The closely related Melampsorella caryophyllacearum also affects Silver-fir, causing Witches'-broom galls

host

Photograph the rust on host plant; ensure you have noted the host-plant species in your comments

Alternates between Silver-fir and Comfrey.