Assessment of Winter Injury in Grape Cultivars and Pruning Strategies Following a Freezing Stress Event

Abstract

Extreme subfreezing temperatures occurred in January 2009 throughout the grapegrowing regions east of the Rocky Mountains. In Ohio, temperature lows ranged between −22 and −31°C, which were considered critical for grapevine productivity and survival. A statewide survey was conducted to assess bud injury in more than 30 cultivars grown at research and commercial vineyards. A pruning study was also conducted at the research vineyard located in Wooster, Ohio, where <i>Vitis vinifera</i> Pinot gris sustained ~90% bud injury after exposure to −26°C. The objectives of the pruning study were to evaluate various pruning strategies and to identify the best pruning practice for a rapid vine recovery. Pruning consisted of four treatments with increasing buds retained per vine. Winter injury assessment showed the greatest bud injury in the sensitive cultivars of <i>Vitis vinifera</i> and the least injury in new hybrid and American cultivars. Cordons, trunks, and whole vines also sustained winter injury, but there were no differences among the pruning treatments. Yield increased and cane pruning weights decreased with decreasing pruning severity resulting in unbalanced grapevines from all treatments except the 5-node hedging treatment. Furthermore, there was no negative carry-over effect of pruning type on bud fruitfulness in the subsequent year. It was concluded that even though pruning had no physiological impact on vine recovery following extensive winter injury, 5-node hedging is recommended for practical and economic reasons.