Good Fruit Grower

July 1

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28 JULY 2014 GOOD FRUIT GROWER I n the field, Washington State University's new apple, WA 38, which has been named Cosmic Crisp, has unique behavior as compared to most scion vari- eties. Since 2008, trees have been grown in four locations across Washington and evaluated for hor- ticultural traits and storage behavior by Washington Tree Fruit Research Commission scientists Tom Auvil and Dr. Ines Hanrahan and WSU apple breeder Dr. Kate Evans, with the help of an industry advisory group. In addition, WSU tree fruit physiologist Dr. Stefano Musacchi is lead- ing the evaluation of two newly established plantings at the university's research orchards near Wenatchee and Prosser. WA 38 is a vigorous tip bearer, similar to Granny Smith (see Figure 1). The good side of this double-edged sword is that it does well in replant sites. The bad news is that Granny Smith is often managed to minimize light expo- sure to fruit, but fruit from WA 38 is red and needs light to have consistent color. The Granny Smith tree growth habit also develops blind wood. High vigor, larger caliper branches seem to have much more severe blind wood. This can be miti- gated by bending limbs as they grow beyond 12 inches long, or by removing the very large limbs to allow smaller limbs to reestablish. A pruning stub with a viable bud should be left, which may require a two- to four-inch stub. Musacchi is working on management strategies to minimize the negative aspects of this growth habit and is already seeing considerable success. Unlike most other varieties, WA 38 produces good quality fruit on spurs and one-year wood. Russet, parrot beaks, and small fruit are common maladies seen on fruit originating from one-year wood on many varieties, but not with WA 38. The flower clusters typically will slough to a single fruit (see Figure 2). WA 38 has not required as diligent hand thinning as Fuji or Red Delicious. The tree's susceptibility to mildew is similar to Granny Smith and not as debilitating as Honeycrisp. Fire blight will catch WA 38. It blooms later than Cripps Pink and Scifresh (Jazz), but does not have as much late bloom as some other varieties. In 2014, in both Prosser and Quincy, we observed secondary bloom of a cluster or single flower as late as May 21 scattered through mature trees and second- or third-leaf grafts (see Figure 3). This should be a consideration during high to extreme fire blight con- ditions, such as those of 2014. GOOD TO KNOW A research report from Tom Auvil, Ines Hanrahan, Stefano Musacchi and Kate Evans How to grow Cosmic Crisp WA 38 is grower friendly and should present minimal harvesting, storage, or packing problems. Figure 1. Shoot growth primarily at the end of branches, typical of a type-4 or tip-bearing scion. Stark Bro's Nurseries & Orchards Co. 10#PYt-PVJTJBOB.0tt'BY Got fruit trees? Call 800-435-8733 to place your 2016 pre-bud order today! 4UBSL#SPT8IPMFTBMFDPN A Growing Legacy Since 1816 MARCHANT LADDERS, INC. Quality Ladders Since 1978 509-882-1912 Grandview, Washington Heavy Duty Top Bracket Heavy Duty Bottom Step Extra support on longer steps, all steps 3" wide • Buy factory direct • BEST ladder at the BEST price • Available 6 to 16 foot Built of sturdy, lightweight ALUMINUM— Specifically for agriculture "The Standard for the Serious Orchardist" PHOTOS COURTESY OF WSU

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