Welcome back to the Wisconsin Fruit Newsletter! As we enter another growing season, I’ve received several inquiries about making lime sulfur applications to dormant vines to control disease ahead of the growing season. Many wonder if this practice works or if it’s a waste of a spray. The answer depends on the diseases you are trying to manage.

Several fungal pathogens overwinter on canes and mummies in the canopy. This can serve as a source of inoculum during the growing season if not managed. Winter sanitation (pruning out diseased tissue and removing mummies) can reduce fungal inoculum, but fungicide sprays can also help minimize disease pressure.

Dormant lime sulfur reduces the amount of overwintering fungal spores from anthracnose, Phomopsis, black rot, and powdery mildew. However, it is most beneficial for the first three diseases listed and is not very helpful for powdery mildew control. This is because powdery mildew continues producing secondary infections throughout the season, and this is primarily what drives the disease. So, early season sprays will be much more beneficial for powdery mildew control than those applied during dormancy. Phomopsis, black rot, and anthracnose infections are driven by overwintering (primary) inoculum, therefore dormant lime sulfur applications can reduce infection by these pathogens.

Check out this article to learn more about lime sulfur applications during dormancy: https://fruit.wisc.edu/2021/04/02/re-considering-dormant-lime-sulfur-applications-for-upper-midwest-vineyards/

Midwest Pest Management Guide, 2021-2022: https://ag.purdue.edu/hla/Hort/Documents/ID-465.pdf

New Version! 2022 Organic Production and IPM Guide for Grapes: https://ecommons.cornell.edu/handle/1813/42888.3

This article was posted in Disease, Grapes and tagged disease, disease control, dormant lime sulfur, dormant lime sulfur applications, dormant vines, Grapes, Leslie Holland, vineyard.