Issue link: https://read.dmtmag.com/i/751050
www.goodfruit.com GOOD FRUIT GROWER DECEMBER 2016 41 much higher than the desired target and reached 7.7 tons per acre, compared to the mechanically pruned vines of 6.8 tons per acre, which was consistent for both seasons. The mechanically pruned fruit had much greater soluble solids, berry weight, anthocyanins and pH than the hand-pruned fruit. Wines made from the mechanically pruned vines had greater amounts of phenolics than the hand-pruned wines. The adjustments were not applied because they were not needed. During 2016, Keller used the mechani- cal harvester to remove some of the crop. The harvester ran at a high speed with only a little beating action. The mechan- ical thinning took place around the lag phase stage of growth. He estimated that about 15 percent of the crop was removed. A late harvest treatment was also applied. Thus far, Harbertson has not observed significant differences between the mechanically pruned, plus mechanically thinned fruit and the fruit that was only mechanically pruned. In 2016, measure- ments of cluster temperatures and tannin extractability were also collected. At press time for Good Fruit Grower, wines from the treatment vines were in secondary fermentation. The WSU researchers hope to extend the trial for at least another year to confirm results and assess vineyard productivity. Once the project is finished, details will be reported to the industry. Serendipity "It's obvious that the results of this experiment were skewed in the second year by high yields in the hand-pruned treatment — yields that were twofold greater than we targeted," Harbertson said. But the mishap provided interesting results. The serendipitous higher yields seem to suggest that wine quality is not impacted by mechanical pruning per se. "The results suggest that as long as the mechanical pruning does not lead to overcropped vines, the wines produced will have high concentrations of phe- nolics," he said. Preliminary data indi- cate that for certain tiers of wine styles, mechanical pruning and thinning are not detrimental. With a looming shortage of skilled workers and continued growth in the industry, data from this trial will be wel- come science to the state's wine indus- try. The ability to more fully mechanize vineyard tasks like pruning and thinning could help the Washington wine industry continue its rapid growth despite labor shortages and help growers stay compet- itive in the premium wine market. • Melissa Hansen is the research pro- gram manager for the Washington State Wine Commission. TJ MULLINAX/GOOD FRUIT GROWER Workers prune a Cabernet Sauvignon block at Mercer Canyon Estates vineyard north of Alderdale, Washington.