Effects of Early Shoot Trimming of Varying Severity on Single High-Wire Trellised Pinot noir Grapevines

Abstract

Amid growing concerns over global warming and available management strategies to reduce cluster temperature and prevent overheating and sunburn damage, there is increasing interest in sprawling, nonpositioned canopies as an alternative to traditional vertically positioned ones. However, management of sprawling canopies requires adjustments to maintain a mostly erect growth pattern during the season. A three-year study (2009–2011) was carried out to investigate the performance of 15-year-old Pinot noir grapevines trained to a single high-wire trellis subjected to prebloom shoot trimming to retain seven (T7) or eleven (T11) main stem leaves. There were significant year × treatment interactions: with a low crop and weather conducive to posttrimming lateral regrowth in 2010, trimmed vines had higher leaf area, soluble solids concentration, pH, total anthocyanins, and cluster rot incidence than control vines, whereas in 2009 and 2011, the overall must compositional pattern was reversed due to suboptimal leaf-to-fruit ratios in the trimmed plots. The effects linked to this necessary operation are highly dependent on unpredictable weather occurring after shoot trimming; hence, the milder trimming severity (T11) may more successfully balance the need to induce a still mostly erect canopy while retaining sufficient vine leaves to buffer possible weak lateral formation after trimming. This paper provides new and useful knowledge for improved canopy management in trellises with free shoot growth due to the absence of foliage wires.