Evaluating the effects of early pruning, leaf removal, and shoot thinning on ‘MidSouth’ grapes over two consecutive vintages in south Mississippi

Authors: WILLIAMS, HALEY - Mississippi State University; STAFNE, ERIC - Mississippi State University; ZHANG, YAN - Mississippi State University; CHANG, SAM, K.C. - Mississippi State University

Submitted to: Agronomy Journal
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/24/2023
Publication Date: 1/27/2023
Citation: Williams, H., Stafne, E., Zhang, Y., Chang, S. 2023. Evaluating the effects of early pruning, leaf removal, and shoot thinning on ‘MidSouth’ grapes over two consecutive vintages in south Mississippi. Agronomy Journal. 13:368. https://doi.org/10.3390/agronomy13020368.
DOI: https://doi.org/10.3390/agronomy13020368

Interpretive Summary: The ‘MidSouth’ grape, a bunch grape grown in south Mississippi, has low sugar levels and high acidity, making it less suitable for winemaking. Different vineyard management practices were evaluated on 'MidSouth' in hopes of improving these fruit qualities. Early pruning with and without leaf removal, normal pruning with post-fruit set leaf removal, and normal pruning alone were tested in one two-year study, and another study looked at post-fruit set leaf removal, shoot thinning, or no additional treatments. Results showed that early pruning with leaf removal reduced the number of berries per cluster, cluster weights, crop yields, and the Ravaz index (a measure of vine balance). However, early pruning results varied each year, and normal pruning treatments didn’t show significant differences from one another. Shoot-thinned vines had lower yields and Ravaz index but higher sugar content. Leaf removal in the second study led to lower juice pH and lower yields. Overall, these practices did not sufficiently improve 'MidSouth' grape quality. Therefore, to avoid ineffective or even detrimental effects, it is recommended that grape growers stick with normal pruning without additional canopy management treatments for 'MidSouth' grapes in south Mississippi.

Technical Abstract: Yield components and fruit composition of ‘MidSouth’, an interspecific hybrid bunch grape (Vitis spp.) with relatively low total soluble solids and high titratable acidity, was evaluated in south Mississippi to determine if treatments consisting of early pruning, early pruning with pre-bloom leaf removal, normal pruning with post-fruit set leaf removal, or normal pruning in one study, or post-fruit set leaf removal, post-fruit set shoot thinning, or neither leaf removal nor shoot thinning in a second study could improve these qualities. Early pruning with leaf removal reduced berries per cluster, cluster weights, yields, and Ravaz index. Early pruning treatments had inconsistent results from year to year, and normal pruning treatments were not often significantly different. Shoot thinned vines had lower yields and Ravaz index and higher total soluble solids. Second study leaf removal vines had lower juice pH in 2020 and lower yield per vine in 2021. These findings show that ‘MidSouth’ can be altered by these practices, but they did not appear to sufficiently alter ‘MidSouth’ quality. Thus, early pruning with or without leaf removal, normal pruning with leaf removal, and shoot thinning are not recommended for ‘MidSouth’ in south Mississippi, and normal pruning without these practices should be continued.