fire blight

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

• noun A disease of plants in the rose family, especially apple and pear trees, caused by the bacterium Erwinia amylovora and characterized by blackened flowers, leaves, and branches.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun a bacterial plant disease that mainly affects apples, pears and some other members of the Rosaceae family

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

• noun a disease blackening the leaves of pear and apple trees