Hemant Gohil, Lynn Mills, and Markus Keller*
*Washington State University, Irrigated Agriculture Research and Extension Center, 24106 N Bunn Rd., Prosser, WA 99350 (mkeller@wsu.edu)

In Washington State, some of the older vineyards have experienced repeated cold injury, reducing their productivity. During 2014 to 2016, a field trial was conducted in an own-rooted Merlot vineyard planted in 1981 to test the potential of various pruning methods to revive cold-injured vines. Treatments were: 1) standard spur pruning (control); 2) modified kicker cane – 3 short canes were trained onto the cordon while the remainder of the cordon was disbudded; 3) disbudding – all buds were removed from the cordon; and 4) chopped cordon – the cordon was removed by cutting the trunk 10 to 15 cm below the cordon wire, and one strong sucker was trained onto the wire to reestablish the cordon. Vine recovery was measured through 2016 by determining pruning weight, yield components, and fruit composition. In 2014, shoot growth and periderm formation were the highest in chopped cordon, indicating the fastest vegetative recovery, albeit with no crop. The three-year average yield (3.9 kg/vine) and cumulative yield (11.8 kg/vine) in kicker cane was significantly higher than in other treatments. Cluster numbers were higher, but cluster weights were lower, in kicker cane in 2016. Pruning weight measurements indicated that kicker cane had higher vigor compared to standard spur and disbudding. In 2016, the yield to pruning weight ratio for kicker cane (6.3) was in the recommended range (five to 10), while for other treatments, it was under five. Overall fruit composition remained similar in all four treatments during all three years, except for a slight increase or decrease in soluble solids, titratable acidity, or pH, only in one year. Observations indicate that chopped cordon promoted greater uniformity, but kicker cane offered higher economic returns during the three study years.

Funding Support: This project was funded by Washington State Grape and Wine Research Program, with in-kind contributions from Rosebud Vineyard and Ste. Michelle Wine Estates.