Don’t let color fool you into jumping the gun. Rely on the starch scale to decide when to harvest WA 38 apples.
That’s one of the key messages from a series of harvest timing field days throughout the state, as researchers and industry officials prepare growers gearing up for the first commercial crop of the WA 38, bred by Washington State University and marketed as Cosmic Crisp.
The bicolored apple ripens slowly and has a long harvest window.
“You are not in a particular rush to pick this apple,” said Ines Hanrahan, executive director of the Washington Tree Fruit Research Commission, to about 50 people at a field day Monday afternoon at a Kershaw Fruit and Cold Storage block in Sunnyside.
With Research Commission funding, researchers developed the six-point starch scale and came up with empirical thresholds for marketable quality fruit, Hanrahan said. WA 38 apples must clear at least 2.5 on a six-point starch scale before picking and 5 before selling, minimums agreed to by a marketing committee of several shippers. Apples must reach 50 percent red color to classify as Extra Fancy, also decided by the committee.
Color alone, however, can lead to confusion. The bicolored WA 38 develops a rich red hue before it’s fully mature, Hanrahan said. Meanwhile, pressure tests can vary on mature apples.
The starch-staining pattern in WA 38 apples tend to develop in either floral or radial patterns, so Hanrahan and her colleagues developed a visual chart for both. The university created illustrated posters and index cards of the scales and instructions on how to use them at http://treefruit.wsu.edu/wa38-starch-scale/. Waterproof copies are also available upon request from the commission.
Hanrahan also warned growers that starch patterns may take longer to develop in the WA 38 than other varieties, anywhere from 5 minutes to 30 minutes, especially if it’s a cold day.
She also stressed that 2.5 is the minimum level on the starch scale. The apple ripens slowly, so growers can wait to instruct their crews to pick in one pass. Picking anywhere from 2.5 to 4.5 on the scale will result in fruit that stores well, she said.
However, researchers do not recommend using plant growth regulators to prevent early dropping, at least as far as they have observed so far, she said. The stems do not detach easily.
There is no advantage to picking early anyway. Proprietary Variety Management, contracted by the university to commercialize the WA 38, has set Dec. 1 as the release date for third-leaf apples and Jan. 1 for second-leaf apples, dates also agreed to by the marketing committee.
The company, usually called PVM, anticipates about 400,000 boxes of Cosmic Crisps reaching the market this season, Tyler Brandt, vice president, said.
WA 38 maturity field days continue this week and next. For times, dates and locations, visit http://treefruit.wsu.edu/event/wa-38-cosmic-crisp-maturity-field-days-pasco/
—by Ross Courtney