Venkateswara Rao Kadium, Zhuoyu Wang, Zach Miller, and Andrej Svyantek*
*Montana State University, 580 Quast Ln, Western Agricultural Research Center, Corvallis, MT, 59828 (andrej.svyantek@montana.edu)

Commercial grapevine production is relatively new to Montana. Cultivar planting decisions and crop management are key concerns for new grapegrowers and winemakers. Two cultural practices, cluster thinning and fruit zone leaf removal (FZLR), are employed by producers attempting to improve fruit chemistry in western Montana, where vineyard sites rarely exceed 1100 accumulated growing degree days (base 10°C). Due to producer and winery interest, FZLR was examined during the 2022 growing season within a replicated grapevine variety trial located in Corvallis, MT, using seven interspecific cultivars of grapevine (Vitis spp.). Five were red wine grapevines (Crimson Pearl, Hasansky Sladky, Frontenac, Petite Pearl, and Verona) and two were white wine grapevines (Frontenac gris and La Crescent). FZLR was conducted two weeks after full bloom for each cultivar by removing leaves and laterals from nodes one to six within the fruit zone of treated vines. Across all genotypes, Crimson Pearl had the lowest soluble solids content (16.7) and Hasansky Sladky had the greatest (24.2). FZLR treatments altered pH, with control vines having higher pH (3.31) than treated (3.25). Titratable acidity, a key concern for winemakers, was not altered by canopy management during the 2022 season. Crimson Pearl, Hasansky Sladky, Frontenac, and Verona were fermented to assess the effect of FZLR on final wine chemistry. FZLR negatively impacted ethanol content while increasing glycerol and total polyphenol content of red wines. While FZLR is a common cultural practice employed by grapegrowers in Montana targeting reduction of acidity, there was no clear evidence of this desired outcome in the variety trial evaluated. However, further examination of wine may reveal chemical outcomes that justify continued examination of canopy management practices for western Montana.

Funding Support: Specialty Crop Block Grant