Issue link: https://read.dmtmag.com/i/629538
www.goodfruit.com GOOD FRUIT GROWER FEBRUARY 1, 2016 15 in storage or export losses. Bartlett is susceptible to a number of storage disorders, including pink end, senes- cent scald, senescent core breakdown and yellowing. Starkrimson is prone to senescent core breakdown and disorders caused by low oxygen or high carbon dioxide levels. A preharvest application of ReTain can inhibit the fruit's ethylene production during storage, reducing senescent disorders and extending the storage life of Bartlett pears, Wang reported. The closer to harvest it is applied, the more effective it is, but the product has a seven-day preharvest interval. He recommends applying between a half and one pouch (60 to 120 ppm) of ReTain one week before harvest and picking the pears at 19 pounds pressure. He recommends the same treatment for Starkrimson, though they should be picked at 15 to 14 pounds pressure. Scientists at the University of California, Davis, have done trials looking at the effect of Harvista on the stor- ability of Bartlett pears. They found that Harvista had no effect on the color of the stored pears and little effect on firmness, but it did reduce senescence disorders. However, Wang found that the postharvest formulation of 1-MCP, SmartFresh, was more effective at increasing the storability of European pears. SmartFresh SmartFresh applied after harvest at 300 parts per billion helped maintain the green color of Bartlett pears and reduced senescence disorders while also allowing the pears to recover their capacity to ripen after being stored for four months. But results with SmartFresh were also inconsis- tent, Wang said. Scientists believe that the effects of SmartFresh are influenced by harvest maturity of the fruit, the elevation of the orchard, the time that elapses between harvest and treatment, and the concentration of ethylene in the storage room. Tests with Starkrimson pears using SmartFresh at 300 ppb showed that after four months in storage at 30°F, the pears did not develop any senescence disorders and had less decay, but they failed to ripen when held for seven days at room temperature. However, they did ripen if stored for more than two months and held for 14 days at room temperature. Tests with Bosc showed that SmartFresh-treated fruit retained firmness, sugar and acid levels and green color better than untreated fruit, and sensory panelists preferred the treated pears because of their crunchy and juicy texture. The treatment also reduced decay caused by bull's-eye rot, phacidiopycnis rot and cladosporium rot. Wang stressed that MCP is not a fungicide but increases the fruit's resistance to decay. In d'Anjou pears, SmartFresh applied at 150 to 200 ppb shut down ethylene synthesis, controlled superficial scald and extended the storage life. The product must be applied within three weeks of harvest, otherwise it will not control scald. Wang conducted laboratory trials in which d'Anjou pears were either treated with the antioxidant ethoxy- quin or ethoxyquin plus 100 ppb of SmartFresh before being put into low-oxygen storage for eight months. Pears treated only with ethoxyquin had 6 percent scald, 6 percent speckling and pithy brown core, and 3 percent decay. Pears treated also with SmartFresh had none of those disorders. However, special steps need to be taken in order for the pears to recover their capacity to ripen after storage. The pears can be stored at a higher tem- perature than normal and held in controlled-atmosphere storage. Or, ethylene can be applied with the SmartFresh. Alternatively, the pears can be conditioned with ethylene after storage. In trials in commercial packing houses in Washington and Oregon, however, SmartFresh applied at a rate of 100 ppb was not enough to control superficial scald or extend the storage life of the fruit. Results were incon- sistent, with perfect control of scald in some lots and no response in others. "A hundred parts per billion works well in the lab, but in big CA storage rooms it's not high enough," Wang told the Fruit School. •