Issue link: https://read.dmtmag.com/i/50987
before the virus can be transmitted by insects or root grafts to neighboring trees. A tree on Mazzard that becomes infected will decline slowly, giving the virus an opportunity to spread. Meyer said he suspects that the Krymsk rootstocks, which originated in Russia, are better able to withstand harsh conditions, whether extreme heat or cold. Meyer noted that on hot afternoons in August or September, if the trees are stressed, the leaves on Gisela rootstocks often seem cupped, but leaves on Krymsk lay flat. It's been reported that K.6 performs better than G.6 in Cali- fornia's hot areas. Long said this is based just on grower observations so far and has not been researched. Training systems Meyer uses the central leader, steep leader, and Kym Green Bush systems. Long said a trial he conducted at Greg Johnson's orchard in The Dalles indicates that central leader trees come into production earliest because of less pruning, but by the fifth leaf, the KGB trees outyield the other sys- tems. Pickers are able to pick more fruit per minute on the KGB system than in the other systems because the KGB is a true pedestrian orchard. "Any time you have to deal with a ladder, it slows your picker down," he said. "Their productivity on the KGB was higher." Long also found in the Johnson trial that in the early stages there was more labor involved in training the cen- tral leader than the other two systems. "It's easier to get that balance with Krymsk 5 than it is with some of the other rootstocks." —Lynn Long Long provided some guidance on how to prune trees on productive root- stocks. Any wood that is weak or below horizontal should be removed in the dor- mant season because they typically will tend to overcrop with small cherries and there will be no new growth at the tip of the shoot. New leaves are needed in order to size the fruit, he explained. Otherwise, the shoot will draw resources from the rest of the tree. One-year-old wood should be tipped annually during the dormant season to reduce the coming season's pro- duction and encourage branching and growth of new leaves. Spurs should be renewed by cutting into older wood because the best quality fruit will be grown on young spurs. No spurs should be older than five years, so about 20 percent of the wood should be renewed every year, whether the system is the KGB, central leader, or Upright Fruiting Offshoots (UFO), Long said. Branches in the top of the tree should be cut in sum- mer, after harvest, to reduce the vigor of the top. The rest of the cuts are done during the dormant season to invigorate the bottom of the tree. However, Meyer said with his Chelan trees, which lack vigor, he plans to cut the tops back in the winter. "With any other variety I would come in postharvest and take the tops down," he said. "With the Chelan, I will probably winter top them because of the lack of vigor." Long has written an article on how to prune cherry trees on productive rootstocks, which can be downloaded from http://ir.library.oregonstate.edu/xmlui/handle/1957/ 20783. • www.goodfruit.com GOOD FRUIT GROWER DECEMBER 2011 57