noun
: any of various diseases of cultivated plants caused by fungi or bacteria and producing dark brown discoloration and decay: as
a. : a disease of the apple, pear, and quince caused by a fungus ( Physalospora cydoniae )
b. : a disease of the grape caused by a fungus ( Guignardia bidwellii ) — see grape rot
c. : a disease of cabbage and related plants caused by a bacterium ( Xanthomonas campestris )
d. : a disease of the sweet potato caused by a fungus ( Ceratostomella fimbriata )
e. : a disease of the potato caused by a bacterium ( Erwinia atroseptica )