Good Fruit Grower

May 15

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N ew information emerging from cherry powdery mildew research shows the potential importance of managing the disease in the orchard throughout the season, not just through harvest. Cherry powdery mildew (Podosphaera clandestina) is a chronic and serious disease in many cherry orchards. High levels of disease can result in the entire crop being rejected for the fresh market. Although fruit infec- tions are the primary concern, mildew is commonly found on foliage. Infected leaves then serve as sources of inoculum for later fruit infections and are also where the fungus forms structures to survive the dormant season. Dr. Gary Grove, plant pathologist at Washington State University and direc- tor of WSU's Irrigated Agriculture Research and Extension Center in Prosser, has studied cherry powdery mildew for years, evaluating fungicide efficacy and developing resistance management and control strategies. Of late, he's looked at ontogenic resistance (age of fruit-related resistance), improved fungicide timing, and importance of season-long disease control. Research he conducted last year suggests that cherries may be unlike grapes and hops that develop age-related resistance to the disease as berries and cones mature. Cherries appear to be susceptible to powdery mildew throughout the sea- son in all growth stages but there may be a period of peak susceptibility. In wine grapes, fungicide sprays long after bloom to ward off fruit infection are unnecessary because berries become resistant to the infection. However, foliar sprays are often still needed to manage the disease on foliage. Grove was hoping to find a similar stage in cherry fruit growth that became resistant to powdery mildew, but no such luck to date. 24 MAY 15, 2014 GOOD FRUIT GROWER Cherries Mildewed cherries in the field. "Bird Gard has been phenomenal! With the lack of birds present and the labor savings, I would say this is the best bird control device on the market. I'm now a Bird Gard believer, and you can quote me on that!" Keep Birds Out GUARANTEED! 888-332-2328 Heath Cleveringa Washington Fruit & Produce Try Bird Gard for an entire YEAR. If you are not completely satisfied with your results Simply return it for a full refund of your purchase price. Season-long mildew control? A build-up of spores after harvest can increase disease pressure the next year. by Melissa Hansen

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