Effect of Pruning on Recovery and Productivity of Cold-Injured Merlot Grapevines

Abstract

A field experiment was conducted to determine effects of pruning time and bud number on vine recovery and performance following cold injury to trunk tissues. Own-rooted Merlot grapevines planted in 1999 and trained to a bilateral cordon with vertical shoot-positioning were pruned in 2003 and 2004 as follows: prebudbreak spur pruning, postbudbreak spur pruning, prebudbreak spur pruning with late repruning (double pruning), minimal pruning, and minimal pruning with disbudding of all nodes. On average, 25% of buds were killed by cold temperatures in late fall. Trunk injury, rated as tissue browning on adjacent vines, varied from 20 to 100% phloem injury with little xylem injury. Phloem injury had virtually no effect on budbreak, growth, fruiting, and fruit composition in the two following seasons. Differences in bud number per vine due to pruning treatment led primarily to equivalent differences in shoot numbers, cluster numbers, and yield. Minimal pruning resulted in the highest yield in both seasons, while double pruning and disbudding resulted in the lowest, but even disbudded vines grew fruitful shoots from basal and latent buds. Overall yields were low and fruit composition was unaffected by the pruning treatment, although soluble solids was negatively correlated with yield. Despite the two warm seasons, most of the vines, including those with high shoot and cluster numbers, did not collapse later in the season. Results indicate that pruning time and bud number did not influence vine survival and recovery from cold injury and had little effect on subsequent growth and vine performance.