fire blight

A destructive disease of apple and pear trees, caused by a bacterium (Erwinia amylovora) that blackens the leaves and kills the branches.

A bacterial disease of apple, pear, firethorn, hawthorn, and related plants. The disease causes sudden browning and death of small branches or entire limbs of trees.

The noun has one meaning:

Meaning #1: a disease blackening the leaves of pear and apple trees
  Synonym: pear blight