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Diseases & Disorders slowing down the amount of carbon diox- ide that will be released." Research has shown that managing the factors that affect fruit respiration (ethylene, stage of fruit development, atmosphere, and tem- perature) can help control carbon dioxide injury. Management tools Harvest maturity: Fruit maturity at harvest makes a big difference in the amount of respiration and ethylene pro- duced by the fruit. Apples picked early in the season produce very little ethylene, and there's little respiration (carbon diox- ide) produced during storage. "But the later you pick, the higher the capacity for the fruit to produce carbon dioxide, which adds to the challenge of limiting carbon dioxide in the atmosphere," Mattheis said. "That's why fruit is picked early if it's going to be stored for long periods—the matu- rity stage naturally helps keep the carbon dioxide and respiration rates lower." Mattheis noted that in carbon dioxide- sensitive varieties, apples harvested early tend to have increased peel injury risk, while fruit harvested later have more internal injury. Matching fruit develop- ment to storage potential in sensitive vari- eties is one tool to help manage carbon dioxide injury. Temperature management: Tempera- ture control is important and provides an avenue to manage injury, he said. Low temperatures help to reduce production of carbon dioxide. Control carbon dioxide accumulation: Mechanical devices like scrubbers can remove carbon dioxide from the atmos- phere. Low oxygen also reduces respira- tion, the driver for carbon dioxide production. However, a small amount of carbon dioxide in the atmosphere can actually help slow down the carbon diox- ide production by the fruit, Mattheis said. "The amount of carbon dioxide is impor- tant and the amount of oxygen is impor- tant. Lower amounts of oxygen mean that you need to keep the carbon dioxide lev- els low as well." Research showed much more injury at 5 percent carbon dioxide than 0.5 percent. Mattheis acknowledged that 5 percent carbon dioxide is an artifi- cially high rate, but it's used for research purposes to help show effects. Exposure and SmartFresh: If you can delay when fruit is put into controlled atmosphere, you can avoid some risk of injury, Mattheis said. A study found less injury on fruit that was treated with MCP and put into CA after a delay of five weeks. "There's less risk of carbon dioxide injury when fruit is held in regular air, and the SmartFresh maintained the quality of fruit during this period and kept it from getting soft, even though it was not held in CA." Carbon dioxide sensitivity is highest right after harvest on mature fruit, so it's important to have a strategy for sensitive varieties before they arrive at the cold storage. When ethylene is inhibited, as is the case after SmartFresh treatment, the fruit tends to have a prolonged sensitivity to carbon dioxide. www.goodfruit.com High Potency CYD-X® Mattheis added that because carbon dioxide injury is a result of oxidative metabolism, reducing potential for oxidative injury through the application of DPA (diphenylamine) may be a treatment to consider. Support for his research comes from the Washington Tree Fruit Research Commission and AgroFresh. • HP The most potent codling moth virus...ever. [] ©2012 Certis USA www.CertisUSA.com GOOD FRUIT GROWER FEBRUARY 15, 2012 27