Black rot, caused by the fungus Guignardia bidwellii, is the most serious disease of grape in Tennessee. Precautions must be taken to protect grape plantings from this disease. The black rot fungus can attack many plant parts, including the leaves, shoots, flowers, tendrils and fruit. The most damaging aspects of black rot are rotting of the berries and loss of leaves.
"SP277-J-Black Rot of Grape," The University of Tennessee Agricultural Extension Service, SP 277J-2M-7/01(Rev) E12-4615-00-004-02, https://trace.tennessee.edu/utk_agexdise/43