UCCE Sacramento County chemical bunch rot trials First two sentences: Summer bunch rot is a very serious problem for wine grape growers in the San Joaquin Valley. Tight clustered varieties, i.e., Zinfandel, Chenin blanc, Petite Sirah, etc., are most susceptible. Duncan_BunchRot_1995.pdf File Size0.5 MiB DateJune 5, 2013 Downloads1098 AuthorRoger Duncan