barberry-fungus

from The Century Dictionary.

• noun A fungus which attacks the leaves of the common barberry, formerly known as Æcidium Berberidis, but now proved to be the æcidiospore stage of the red and black rust (Puccinia graminis) which is found upon wheat, oats, other kinds of grain, and various species of grass. Also called barberry-rust or barberry-clustercups. See cut under Puccinia.