wheat rust

from The American Heritage® Dictionary of the English Language, 5th Edition.

• noun Any of several diseases of wheat caused by rust fungi, especially a destructive stem rust characterized by reddish blisters that turn black at the end of the growing season.
• noun Any of several rust fungi of the genus Puccinia that cause these diseases, especially a form of P. graminis that affects stems.

from the GNU version of the Collaborative International Dictionary of English.

• A disease of wheat and other grasses caused by the rust fungus Puccinia graminis; also, the fungus itself.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun rust fungus that attacks wheat