Good Fruit Grower

February 15

Issue link:

Contents of this Issue


Page 10 of 39 GOOD FRUIT GROWER FEBRUARY 15, 2014 11 W hen China reopens its market to U.S. apples, managing crab apple pol- linizers in the orchard for diseases is expected to be part of the new Chinese export protocol. Managing the diseases that brought on the mar- ket closure will take a two-prong systems approach involving both pre- and postharvest, says Dr. Rich- ard (Yong-Ki) Kim of Pace International, a chemical company and services pro- vider. Kim, a former postharvest patholo- gist for Washington State University, is heading a three-year research project that began last year to study disease infection in orchards and packing houses and to develop management strategies for control. China closed the U.S. market in August 2012 after years of detecting various rots in shipments of Red Delicious apples. Red and Golden Deli- cious are the only varieties allowed to be imported. The three fungal diseases detected by China were bull's-eye rot (Neofabraea sp.) and two crab apple canker-based diseases, Sphaeropsis rot (Sphaerop- sis pyriputrescens) and speck rot (Phacidiopycnis washingtonensis). "Reopening the Chinese market for Washington apples is an extremely high priority and impacts future access for all varieties, not only Reds and Goldens," said Dr. Mike Willett, vice president for scientific affairs, Northwest Horticultural Council. "We've lost significant market share since August 2012." Getting U.S. apples back into China is a big deal, Willett said. "The crab apple diseases aren't unique to Red and Golden Delicious orchards. We hope within the coming year to have access for all apple varieties." When China began detecting the apple rots several years ago, the relationship between Man- churian crab apple and the diseases was not well understood, he noted. "When we visited the orchards implicated in the detections, we realized there was a serious disconnect in how crab apple trees were being managed." Manchurian crab apple, widely planted as a pol- linizer in Pacific Northwest orchards, is highly sus- ceptible to speck rot and Sphaeropsis rot and serves as a major source for the inoculum. An effective alternative to using Manchurian crab apple has not been identified. "We found that the lack of crab apple manage- ment was leading to high levels of decay," Willett said. "Most growers are farming Manchurians for the blossoms and ignoring the trees for the rest of the year." Pruning research The disease resides in overwintered fruit and pendant wood, explained Tom Auvil, research associate of the Washington Tree Fruit Research Commission. "Mummified fruit left on the tree and orchard floor are loaded with spores, creating a lot of opportunity to infect the orchard," he said. "If the crab apple trees haven't been pruned, the pendant and flat wood develop cankers and serve as a major source of inoculum. You're then well on your way to continuing the disease cycle in your orchard." Willett, Kim, and Auvil, who shared the podium during a presentation at the Washington State Hor- ticultural Association's annual meeting last Decem- ber, are also involved in the research project to learn the effect of crab apple pruning on speck rot and Sphaeropsis rot. The three-year project, which will conclude next year, has three goals: • Generate practical information on the impact of pruning crab apples in apple orchards as part of a postharvest decay integrated pest manage- ment program. • Understand in-season fruit infection by speck rot and Sphaeropsis rot after pruning crab apple trees. • Evaluate the impact of pruning crab apples on the incidence of the two rots in storage. Pruning research Data were collected in 2013 from three Red Deli- cious orchards in George and Royal City that have A branch of a Manchurian crab apple shows canker disease symptoms. A Manchurian crab apple shows disease- laden, mummified fruit from the previous season alongside crab apples from the current season. This crab apple pollinizer was pruned quickly with a chain saw to remove wood showing canker symptoms. Managing crab apple DISEASES Crab apple disease management starts in the orchard with pruning. by Melissa Hansen "Most growers are farming Manchurians for the blossoms and ignoring the trees for the rest of the year." —Dr. Mike Willett Diseases & Disorders PHOTO COURTESY OF RICHARD KIM PHOTO COURTESY OF TOM AUVIL PHOTO COURTESY OF TOM AUVIL

Articles in this issue

Links on this page

Archives of this issue

view archives of Good Fruit Grower - February 15