Rotting Grapes Don't Improve with Age: Cluster Rot Disease Complexes, Management, and Future Prospects

Cluster rots can be devastating to grape production around the world. There are several late-season rots that can affect grape berries, including Botrytis bunch rot, sour rot, black rot, Phomopsis fruit rot, bitter rot, and ripe rot. Tight-clustered varieties such as 'Pinot gris', 'Pinot noir', and 'Vignoles' are particularly susceptible to cluster rots. Symptoms or signs for these rots range from discolored berries or gray-brown sporulation in Botrytis bunch rot to sour rot, which smells distinctly of vinegar due to the presence of acetic acid bacteria. This review discusses the common symptoms and disease cycles of these different cluster rots. It also includes useful updates on disease diagnostics and management practices, including cultural practices in commercial vineyards and future prospects for disease management. By understanding what drives the development of different cluster rots, researchers will be able to identify new avenues for research to control these critical pathogens.