Issue link: http://read.dmtmag.com/i/769560
14 JANUARY 15, 2017 Good Fruit Grower www.goodfruit.com 2016 confirmed that intense conditioning, utilizing a temperature of 70 degrees F for three to five days, is also effective. At the same time, growers also must be careful to keep carbon dioxide levels below 1 percent. Levels of this gas can increase rapidly because the apples are still respir- ing — taking in oxygen and giving off carbon dioxide. "If you close the door on that room overnight and the car- bon dioxide levels build up, then you can destroy your crop in the conditioning phase before it ever goes into storage," he said. "We've done some work this year try- ing to characterize that, and we found that in as little as 12 hours at a carbon dioxide concentration that is known to be damaging, you can lose a very significant portion of your fruit." Warm fall weather conditions can also affect condi- tioning. An unusually warm autumn in Michigan in 2016 caused many growers to leave their Honeycrisp crop on the trees longer than normal so the apples could develop color. As a result, the apples were a bit over-mature at harvest, and that causes them to become even more sensitive to chilling and to not store as well. For such late-picked Honeycrisp, Beaudry suggests three things: —Condition the fruit at 50 degrees F for the full seven days. —After a day or two in the conditioning room, treat them with 1-methylcyclopropene (1-MCP) at 1 part per million for 24 hours to slow the ripening process. —Maintain carbon dioxide levels below 1 percent throughout conditioning. Storage Following conditioning, fruit then goes into air or controlled-atmosphere storage at 36 to 38 degrees F. The addition of 1-MCP is useful to inhibit ripening. "Because 1-MCP is a gas, you have to seal up the room. That's an issue because the fruit are still comparatively warm coming as they are from the conditioning treatment, which means that their respiratory rate is still very high so they're releasing carbon dioxide," Beaudry said. Hydrated lime can absorb carbon dioxide and it works very well, but he has seen many instances where someone has been rushed and either forgotten to add it or left it in the wrong room. "For the first 30 days, you have to keep carbon dioxide levels low (below 1 percent) and oxygen at 1.5 to 3 percent to avoid those sensitivity issues," he said. "If you treat Honeycrisp like any other apple and give it 3 percent carbon dioxide — a level that is perfectly fine for most apple varieties — you will get at least 20 to 30 percent losses." Even with hydrated lime, carbon dioxide levels can sometimes creep high enough to cause browning in Honeycrisp. The only surefire way to prevent that injury is to use the antioxidant material diphenylamine (DPA), but financial constraints or market demands for organic fruit may discourage this option, he said. Once Honeycrisp has reached 30 days postharvest, Beaudry says carbon dioxide levels can be increased to 3 percent with oxygen concentrations of 1.5 to 3 percent. His storage-temperature recommendations remain at 36 to 38 degrees F for now, but preliminary experiments suggest that slightly lower temperatures may be suitable following some conditioning scenarios. PHOTOS COURTESY RANDOLPH BEAUDRY Surface damage to Honeycrisp is another postharvest challenge. Beaudry says no one knows what causes this disorder — or how to control it. (800) 876-2767 www.westbridge.com ® Prevents Fire Blight in Apples & Pears • Effective alternative to antibiotics • Ideal for IPM programs • Efficacy is comparable to conventional products • No development of pathogen resistance • No pre-harvest interval or chemical residues • Safe for bees and beneficial insects Blossom Protect ™