Potato Grower

damaged regions on tubers that aren't pulled from the line are likely to become apparent to customers after shipping. Once a decision has been made to store frost-damaged potatoes, the storage manager needs to establish priorities for stabilizing the stored material and delivering a saleable product. The highest priority should be maintaining the quality of potatoes that have not been frozen. As potatoes are being loaded into storage, remove as many damaged tubers as possible. Make sure workers have a clear idea of what frost damage looks like. After bin loading, establish conditions that promote wound healing and maturation of the skin while at the same time suppressing the growth and spread of rot-promoting bacteria. The rate of wound healing and the potential for rot both increase rapidly as the storage temperature increases. A temperature of 50 degrees is a compromise that allows for wound healing to occur in about two weeks without strongly promoting the activity of soft rot bacteria. If pulp temperatures are lower than 50 degrees, warm the pile slowly and reduce the humidity in the supply air to well below 95 percent. The optimal relative humidity of the supply air depends strongly on the amount of water that needs to be removed from the pile. An empirical approach to determining an appropriate value is likely to work as well as a theoretical approach. Set the humidity of the supply air so that the return air has a relative humidity of about 90 percent. The goal is to prevent condensation of warm, moist air on cool potatoes as the air moves up through the pile. Condensation promotes disease and slows the removal of water from-damaged potatoes. An unavoidable consequence of this approach is that potatoes on the bottom of the pile will lose water faster than usual and are likely to have pressure flattening and bruising earlier than in a typical year. It may take a few weeks to dry up the damaged tubers. It is important to prevent soft rot from spreading rapidly during this time. Careful monitoring of bins is required to catch problems early. Rapid onset of extensive disease may signal a lost cause that should be shipped as soon as possible. Potatoes with moderate disease symptoms can be treated with products such as FruitGard Wipeout, FruitGard Maintenance and ZeoAir that have chlorine dioxide as the active ingredient. Products containing peroxyacetic acid/ peracetic acid can also be effective in suppressing the spread of soft rot bacteria. Frost-damaged potatoes are not expected to store well or long. Disease is likely to linger and may flare up periodically. It is a challenge to restore acceptable sugars in processing potatoes that have gone off-color. Extra vigilance is required when packing fresh-market potatoes because of concerns over debris and disease. Paul Bethke is a plant physiologist with the USDA's Agricultural Research Service and the University of Wisconsin-Madison. Troy Fishler is the research manager of the potato and vegetable facility at UW's Hancock Research Station. A version of this article previously appeared in the December 2018 issue of Badger Common'Tater. It is published in Potato Grower with permission from the Wisconsin Potato & Vegetable Growers Association. TILLAGE EQUIPMENT P.O. Box 190 • Parma, ID 83660 CALL: 208-722-5116 • FAX: 208-722-6012 EMAIL: parmacom@parmacompany.com Innovative Solutions Since 1907 HIGH SPEED DISC www.parmacompany.com HIGH SPEED DISC • Independent Disc Shanks w/ HD 40mm Disc Hub Bearings • Rear Roller Options: Ring, Roller Pipe, Crow foot, or Chevron Paddle • Floatation Tongue with Lock- Out Feature • Rock Protec tion Cushioned Upper Shank • Heav y Dut y Solid Welded Frame • 2 Floatation Carrier Gauge Wheels • 4 Transpor t Carrier Wheels • 24" Notched Disc Blades Rigid Frame Models 14' - 21' 169415Parma12h.indd 1 1/8/18 10:35 AM WWW.POTATOGROWER.COM 35

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