Good Fruit Grower

May 15

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SWD in Europe populations began to build up in October 2011, and high numbers were still being caught in December. Steve Castagnoli, OSU extension educator, who runs the trapping program, now adds salt to the vinegar traps to prevent them freezing. Flies continued to be trapped through the winter and spring, then populations increased dramatically in July 2012, as the district's cherries started to ripen. When Shearer visited infested orchards, he learned that they were not using spray programs recommended for spotted wing drosophila. They were using neonicotinoid insecticides like Provado (imidacloprid), which do not control that insect. "Some of the responses we got were, 'It worked the year before,'" he said, "but anything would have worked the year before because there weren't any flies in the orchard. The industry now recognizes they have to use effective materials, and they have to shorten up their spray intervals." Shearer has been testing the effectiveness of various materials. Since he doesn't have field populations to work with, he sprays trees with the insecticides, then brings foliage and fruit back to the lab and exposes them to flies. In tests on leaves, the pyrethroids Warrior (lambda-cyhalothrin) and Danitol (fenpropathrin) were extremely effective and long lasting. Delegate (spinetoram) and Entrust (spinosad) were also effective but had less residual effect. Malathion was effective but only for a short time after application. Sevin (carbaryl) was intermediate. However, the results were quite different when he exposed flies to treated fruit. Delegate and Entrust were very effective—more so than Warrior and Danitol. Surprisingly, Sevin was quite effective. Shearer said the surfaces of leaves and fruit hold the products differently because of the waxy layers. Since the flies don't spend all their time just on leaves or just on fruit, a grower has offered to let him do field trials next year to find out how the products affect the amount of fruit damage in the field. Shearer said control failures in orchards were seen when malathion was used repeatedly at seven- to ten-day intervals. In Oregon, growers are now discouraged from using it as a back-to-back stand-alone spray. They're advised to use it just once followed by other insecticides. Fully susceptible Beers said tests on Bing and Sweetheart cherries show that they are fully susceptible to the pest 21 days before harvest, and growers are urged to begin protecting their crops as soon as the first fly is caught in the region. "That's a very conservative approach— we understand that—but until we find out more about the insect and how effective the traps are, we feel this is the best way to go to avoid infestation," she said. Spotted wing drosophila females can lay eggs immediately when they arrive in the orchard, whereas cherry fruit fly females spend about a week foraging on F luctuating populations of spotted wing drosophila from year to year are keeping growers in the Pacific Northwest guessing. After relatively little pressure in 2011, the fly came back with a vengeance in 2012. Growers in Europe are also seeing fluctuations. European Fruit Magazine reports that after serious infestations in 2011, various European countries suffered less damage in 2012. "In 2011, entire crops were destroyed in various places by the actions of this insect," the magazine reported in its January issue. "Therefore, the fear was that in 2012 the damage would be more extensive." Dr. Roland Zelger, researcher with the Laimburg Research Center in South Tyrol, Italy, reported that only small numbers of spotted wing drosophila were trapped during the 2012 growing season, but large numbers were caught in October. Zelger believes spotted wing drosophila will not cause serious damage to orchards every year, but perhaps once every four or five years, though the reason for this is unclear. —G. Warner Domex Superfresh Growers®, owned by the Kershaw family, is using the power of social engagement to fuel real connections with apple, pear and cherry consumers. We are combining the power of consumer connections and category intelligence with global sales and marketing expertise to drive success for our grower partners. Call us today to learn more about growing with Superfresh Growers®. We know what's trending NOW. Our difference makes all the difference™ 151 Low Rd., Yakima, WA. 98908 | GOOD FRUIT GROWER May 15, 2013 21

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