Features Diseases Fruit
Managing early bunch rot in grapes

Botrytis bunch rot, caused by the fungus Botrytis cinerea, is a common problem wherever grapes are grown. The disease can cause serious losses in both yield and quality when weather conditions favour the disease, as is the current case in parts of Ontario. The high humidity and frequent rains we’ve experienced this summer, along with vigorous canopies, have created the perfect storm for bunch rot to develop earlier than usual.

Bunch rot often starts in the centre of a grape cluster, where squeeze is most likely to occur. Infected grapes develop a greyish mould on the surface, which can spread to adjacent grapes and lead to drying and premature cluster drop, as well as post-harvest rot of table grapes. |READ MORE