Issue link: http://read.dmtmag.com/i/76198
Harvest/Postharvest STORING Honeycrisp F or the last ten years, postharvest physiologist Dr. Jennifer DeEll has had an ongoing research project focused on Honeycrisp stor- age issues, trying to identify best postharvest practices for the finicky apple. She's found that successful storage of Honeycrisp is a balancing act—it seems when one storage disorder is solved, another is created. DeEll, research scientist for Canada's Ontario Ministry of Agriculture, Picking apples early can help minimize Food, and Rural Affairs in Simcoe, recently gave an update of her years of Honeycrisp research during a phone interview with Good Fruit Grower. A leading Honeycrisp postharvest researchers, DeEll has helped develop protocols for storing Honeycrisp in northeastern regions, such as Ontario and Nova Scotia in Canada and states like New York, Michigan, and Minnesota. Storage regimes and temperatures recommended for soft scald and soggy breakdown, but can increase bitter pit. by Melissa Hansen Honeycrisp produced in the Northeast may differ from recommended practices in Washington State because of different climates and storage techniques, though generally, traits of the variety are the same. Soft scald Honeycrisp is sensitive to soft scald, a storage disorder related to chilling. Symptoms of soft scald, which is induced by storage temperatures below 3°C (37.4°F) can include external and internal brown lesions that allow secondary pathogens to move into the fruit. Soft scald incidence, which varies from year to year, is aggravated by the following factors: • Advanced fruit maturity at harvest • Growing location and climate (higher incidence after cool, wet summers) • Large fruit • Vigorous trees in heavy soils • Light crops • Fruit mineral content "One of the key things you can do to reduce soft scald incidence is to pick fruit earlier to avoid advanced maturity," DeEll said. In a trial of fruit from the same block picked a week apart and held in regular air storage at 0°C (32°F) for six months, fruit picked September 15 had 7 percent incidence of soft scald, whereas fruit picked September 23 had 47 percent soft scald. Starch, firmness, and soluble solids concentration were similar for the two harvest dates. Soft scald also has been negatively correlated with soluble solids at harvest, a factor often related to weather. The lower the soluble solids, the higher the incidence of soft scald. Tracking soluble solid levels at har- vest from year to year can help growers and shippers see if soft scald trends develop. Soggy breakdown The second major storage problem with Honeycrisp is soggy breakdown, a disorder also triggered by low storage temperatures. Soggy breakdown results in moist, soft, brown, spongy flesh tissue and can be aggravated by factors similar to those of soft scald, except that high crop loads tend to favor higher incidence of soggy breakdown. Soft scald is related more to low crop loads, she noted, which is perhaps why 18 AUGUST 2012 GOOD FRUIT GROWER some years tend to be worse for soggy breakdown and some years for soft scald. To reduce incidence of both soggy breakdown and soft scald disor- ders, DeEll recommends storage temperatures of at least 3°C (37.4°F) and a delay of cooling for seven days, keeping fruit at 10°C (50°F). Fruit held above 50°F can develop greasiness, shrivel, and bitter pit. Balancing act In storing Honeycrisp, it seems that as one disorder is mitigated, a new one develops, like bitter pit. After soft scald and soggy breakdown, bitter pit is the other culprit that you have to play with, she says. "The tradeoff with earlier harvest and delaying cooling to reduce soft scald and soggy breakdown is that you have to play the game of bitter pit," DeEll said. "That's why it's so important to take care of bitter pit in the orchard and to make sure you get a lot of calcium into the fruit to lower the risk of bitter pit. "It's all a game with this apple. It's a balance, juggling the different disorders." Factors that lead to higher incidence of bitter pit are large apples, fruit low in calcium, early harvests, excessive tree growth, overthinning, excessive nitrogen, and warm temperatures. She noted that Honeycrisp is not as prone to bitter pit in Nova Scotia, because summers often have more rain and less sunshine than other regions. MCP effects A postharvest treatment of SmartFresh (1-methylcyclopropene) in Honeycrisp does what it's supposed to—inhibit ethylene production, reduce greasiness, and improve the retention of acidity. But DeEll said it also increases soluble solids. "It's the only variety I've ever seen that has higher soluble solids after treatment," she said. However, MCP does little for firmness because Honeycrisp is naturally firm. She's found no consistent effect on soft scald in Honeycrisp from SmartFresh, though it occasionally reduces soggy breakdown. It can reduce incidence of bitter pit, but it can also increase severity of bitter pit. Additionally, SmartFresh usually reduces senescent browning. For several years, DeEll also has been working with Harvista, the form of MCP applied preharvest in the orchard, to develop data for eventual registration of the material in Canada. She's been most intrigued with results that showed applications of Harvista three and seven days before harvest (each with two harvest picks) significantly reduced postharvest incidence of soft scald. "With Harvista, I've seen good effect in reducing soft scald that I never saw with SmartFresh." The closer to harvest, the better the reduction in soft scald, she said. Fruit treated three days from harvest, held in six months of storage, with no cooling delay to encourage maximum scald incidence, showed soft scald incidence ranging from 5 to 11 percent compared to the control that ranged up to 47 percent scald. Her efficacy work also showed that the full rate of Harvista (120 grams per acre) gave better control of soft scald than a half rate. Carbon dioxide and DPA Controlled atmosphere storage is not currently recommended for Honeycrisp in New York, Michigan, Minnesota, and Ontario because the www.goodfruit.com