The Collaborative International Dictionary of English v.0.48:

Rot \Rot\, n.
   1. Process of rotting; decay; putrefaction.
      [1913 Webster]

   2. (Bot.) A disease or decay in fruits, leaves, or wood,
      supposed to be caused by minute fungi. See Bitter rot,
      Black rot, etc., below.
      [1913 Webster]

   3. [Cf. G. rotz glanders.] A fatal distemper which attacks
      sheep and sometimes other animals. It is due to the
      presence of a parasitic worm in the liver or gall bladder.
      See 1st Fluke, 2.
      [1913 Webster]

            His cattle must of rot and murrain die. --Milton.
      [1913 Webster]

   Bitter rot (Bot.), a disease of apples, caused by the
      fungus Glaeosporium fructigenum. --F. L. Scribner.

   Black rot (Bot.), a disease of grapevines, attacking the
      leaves and fruit, caused by the fungus Laestadia
      Bidwellii. --F. L. Scribner.

   Dry rot (Bot.) See under Dry.

   Grinder's rot (Med.) See under Grinder.

   Potato rot. (Bot.) See under Potato.

   White rot (Bot.), a disease of grapes, first appearing in
      whitish pustules on the fruit, caused by the fungus
      Coniothyrium diplodiella. --F. L. Scribner.
      [1913 Webster]

WordNet (r) 3.0 (2006):

black rot
    n 1: a fungous disease causing darkening and decay of the leaves
         of fruits and vegetables