Issue link: http://read.dmtmag.com/i/76198
Harvista effects on soft scald incidence Soft scald was significantly reduced from preharvest application of 1-MCP. No Harvista Harvista applied 11 days before harvest Harvista applied 15 days before harvest out of storage out of storage 47% Fruit 1 day 7 days 45% 5% 16% 11% 28% Notes: Harvista (1-methylcyclopropene) was applied well before harvest to simulate a later harvest. No cooling delay for fruit before storage. Fruit were held for six months at 0°C. Fruit were held at 21°C after removal from storage for one day and seven days before soft scald evaluation. SOURCE: DeEll and Ehsani-Moghaddam, HortScience 45(3):414-417, 2010. Honeycrisp apples (inset photo left) were treated with Harvista in the orchard close to harvest and held in air at 0°C for six months. Without Harvista (photo at left), Honeycrisp stored under the same conditions had soft scald and secondary rot. DETERMINING Honeycrisp maturity O Honeycrisp apples in a controlled atmosphere trial (above), have a clear lid to allow Jennifer DeEll, right, to monitor conditions without breaking the CA seal. DeEll's most recent Honeycrisp storage emphasis is focused on controlled atmosphere regimes, timing, in combination with or without SmartFresh, and delayed cooling. ne way to reduce soft scald incidence in Honey- crisp is by picking fruit before they are advanced in maturity. But determining optimum maturity in Honeycrisp is difficult because standard indices used for other varieties just don't work well, says a leading postharvest physiologist. "You can't focus on ethylene in Honeycrisp like you do with McIntosh and Empire," said Dr. Jennifer DeEll of Ontario, Canada. "Also, maturity is not always related to the depth of red color." She found maturity indices (starch, firmness, solu- ble solids concentration) to be about the same in a trial of Honeycrisp that was picked when fruit was bright, vibrant red and compared to fruit picked when dull red, fruit that would probably be left on the tree for further coloring and ripening. "They were both about the same when it came to sugars and starch indices," she said. "Red color wasn't effective in determining maturity in this trial." Growers who must hang Honeycrisp on the tree Honeycrisp are sensitive to low temperatures and store better at 3°C (37.4°F), left photo, compared with 0°C or 32°F in the photo above. variety is sensitive to internal carbon dioxide injury. Lim- ited success with controlled atmospheres of 3 percent oxygen with 1.5 percent carbon dioxide have been observed. The recommendation for Nova Scotia storage operators is 2 percent oxygen, 3 percent carbon dioxide, with the carbon dioxide scrubbed out of the atmosphere four to six weeks after storage. A CA trial with 1.7 percent oxygen and no carbon diox- ide greatly reduced the incidence of soggy breakdown compared with 2 percent carbon dioxide. www.goodfruit.com Applying a postharvest drench of DPA (dipheny- lamine) can sometimes reduce incidence of soft scald. In the past, DeEll said, there was little interest in using DPA because of further contamination from pathogens in the drench. But with alternative application methods, such as thermofogging, she believes there will be more interest in using DPA on Honeycrisp. • longer and wait for color are likely increasing the incidence of soft scald later in storage. She recommends starting harvest when the ground color changes from green to yellow and the starch index is around 6 (based on the Cornell chart that goes to 8). Previous research by Drs. Jim Wargo and Chris Watkins determined that the best eating quality for Honeycrisp is around 13 percent soluble solids concentration and 13.5 pounds or greater firmness. "If you don't have the right color when ground color changes from green to yellow and must hang it on the tree longer so you can sell the fruit, that's fruit you don't want to put into long-term storage because it'll be more susceptible to soft scald," she said. —M. Hansen GOOD FRUIT GROWER AUGUST 2012 19 Photos by Jennifer Deell, oMAfrA