Leaf removal supports healthy wine grapes
Wine grape vineyards are vulnerable to fungal diseases that can ruin the grape crop and make the wine unsellable if not managed properly. As more wine producers move toward organic farming or using biodynamic methods, the fungicides producers can use are limited. One nonchemical way to reduce these diseases is to remove leaves in the cluster zone of the vine.
Oregon State University Extension Service researchers are studying timing and intensity of leaf removal and its effects on disease resistance and fruit quality. The researchers’ work has found that leaf removal is crucial to prevent disease when combined with fungicides. Despite these findings, many Oregon winemakers have been shading their fruit instead of removing leaves due to concerns about hot, dry seasons, and the belief that white wine grapes shouldn’t be exposed to the sun.
In response, an educational event was held at the 2024 Oregon Wine Symposium to teach winemakers about the importance of leaf removal and the proper timing and intensity for white wine grapes. OSU Extension’s viticulture team tested single-sided and double-sided leaf removal at the fruit set stage and compared it to no leaf removal. Wines were made and processed with the resulting fruit using standard practices.
Participants tasted three wines without knowing which leaf removal treatment was used. They rated the wines as fruity and bright for single-sided leaf removal, more floral/round/grassy for no leaf removal and tropical for double-sided leaf removal.
The event showed that early season leaf removal can improve disease management and grape/wine quality, especially in organic vineyards and wineries aiming for premium wine production. In follow-up surveys of participants, 71% said they would use single-sided leaf removal early in the season, 15% would remove leaves on both sides, and only 5% would not remove leaves.
View the full statement on the NIDB.
Project supported by State Appropriations. Photo courtesy of Oregon State University Extension Service.
