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black rot[′blak ‚rät]
a grapevine rot, which mainly infects the grapes (occasionally the shoots and leaves); at first small brown spots appear, soon growing larger. The grapes shrivel and become almost black, shot with a bluish color; they become covered with black knobs. The disease appears after prolonged cold rains. A few pathogenes of black rot are known, the most dangerous of which is the ascomycetes Guignardia baccae. The method of fighting black rot is to spray the vines with bordeaux mixture, a pesticide.