Late bunch stem necrosis, indicated by shriveling of the stem, followed by shriveling of the berries, in that order. Photo: Annie Klodd. Author: Annie Klodd. Late bunch stem necrosis (LBSN) is a physiological disorder of grapevines, where the grape clusters shrivel and die during ripening. It is not a disease, so fungicides are not effective on it. However, a large part of what makes this disorder so frustrating is that the causes are not well understood. In collaboration with grape growers and the UMN Grape Breeding lab, we are working to identify potential causes so that we can develop recommendations to control LBSN. Late bunch stem necrosis is a complex physiological disorder of grapevines, where the bunch stems (rachises) shrivel during ripening, followed closely by berry shrivel. This sudden change is frustrating for growers, when seemingly healthy vines produce unusable clusters. LBSN affects vineyards worldwide, but may be caused by a number of environmental stresses...