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WSU Decision Aid System Update September 2023

Written by Liesl Oeller, Washington State University, September 5, 2023

Storage Scald

The DAS apple storage scald model has started. Storage scald is the diffuse browning of the skin of apples or pears that appears after storage. Storage scald is the most economically serious postharvest disorder of apples and pears. The risk of storage scald is correlated with a number of preharvest factors, including variety, maturity, orchard temperatures, fruit color, nutrient content, fruit size, soil moisture content, and spraying.

images of apples and pears with browning of the skin, called storage scald

The appearance of storage scald has been related to orchard temperature during the final weeks of fruit maturation. As the fruit is exposed to increasing periods of temperature below 50°F, the susceptibility to scald decreases. Dr. Eric Curry of the USDA-ARS has shown that when starch content is less than 3 (0 to 6 scale) and 150 hours below 50°F have NOT accumulated, scald potential is likely to remain high. If the starch progresses beyond 3, then maturity will begin to override the requirement for cool temperature and scald susceptibility will decrease. Generally, an uninterrupted accumulation of 150 or more hours below 50°F will result in fruit with low scald potential.

In addition to reporting accumulated hours below 50°F, the DAS scald model provides a graph of scald hours, a weather forecast, and orchard management activities based on current and projected conditions for each station.

To read more about storage scald, check out this article by Dr. Eugene Kupferman, a former WSU extension horticulturist and postharvest specialist.

New Tools

As we come closer to harvest, many DAS models have completed. Now is a great time to use our time machine tool to look back on the season and assess your management timing and effectiveness. This could help make more informed and efficient applications next season.

The DAS spray selection tool is also useful to plan products and application timing for next season. The spray selection tool uses the information from the Washington State University tree fruit crop protection guide and organizes into an easy to use guide. The spray selection tool allows users to select their crop, growth stage, and target pest or pathogen. The guide then shows a list of possible materials to apply, and their efficacy on your target and other important pests.

This fall, the DAS team is also planning on adding new videos to the How To section of the website. These will include tutorials on how to use the new features on DAS, as well as some of our many pest, pathogen, and horticultural models. If you have any suggestions for future how to videos, please let the DAS team know.

For weekly updates on DAS models and tools, subscribe to our mailing list!


Liesl Oeller

Liesl Oeller
Washington State University
(509) 335-5815

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