Canopy management strategies to control yield and grape composition of Montepulciano grapevines

Background and Aims Higher temperature during the season is forcing growers in Central Italy to explore ways to reliably control vine yield and grape ripening, while maintaining grape composition. The most common approaches include altering winter pruning, shoot thinning (St), leaf removal and bunch thinning. These studies, however, rarely evaluated these practices in concert and over multiple seasons. Methods and Results From 2009 to 2013, five treatments were applied to Vitis vinifera L. cv. Montepulciano: winter pruning only (Wp, Control); Wp plus St; St plus pre‐flowering defoliation (St + Dpa); St plus pre‐veraison defoliation (St + Dpv); and St + Dpv plus bunch thinning (St + Dpv + Bt) applied prior to veraison. Effects on canopy architecture, yield, ripening and berry composition were measured. Compared to Wp, St, St + Dpv and St + Dpv + Bt treatments reduced leaf area and leaf layer number in the fruiting zone, while St + Dpv + Bt reduced yield. No treatment slowed ripening. The treatment St + Dpa reduced yield and the incidence of Botrytis cinerea, and improved fruit composition, but increased TSS in berries. All treatments were ceased after 2013 and the vines were pruned in winter only. The treatment St + Dpa imposed in 2013 had a strong carry‐over effect on yield but not TSS in 2014. Conclusions Shoot thinning alone reduced canopy density but failed to reduce yield or improve fruit composition. Both the St + Dpv and St + Dpv + Ct treatments provided a more open fruit zone, had no effect on yield and increased TSS in fruit at harvest. Shoot thinning plus pre‐flowering defoliation decreased yield and improved berry composition in a Mediterranean climate; however, given its observed carry‐over effects on yield this approach should be applied only in alternate years, suggesting the need for further research exploring additional viticultural practices. Significance of the Study Despite some benefits of St, defoliation and bunch thinning on their own or even in concert, no combination tested was consistently effective for controlling vine yield and grape ripening, while maintaining grape composition.