Good Fruit Grower

August 2012

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GOOD TO KNOW A research report from Jacqueline Gordon and Ines Hanrahan, Washington Tree Fruit Research Commission S New Honeycrisp disorder found A new "stain" disorder was discovered in Controlled Atmosphere stored fruit. ince Honeycrisp was first planted in Washington State in 1999, the area plant- ed in the state has increased to 9,100 acres. Based on information obtained from the Washington Growers Clearing House Association, 31 percent of last year's Washington crop was stored until after January 1, 2012. Some of that fruit was held in controlled atmosphere (CA), mostly without major problems associated with the changed storage atmosphere. The most prevalent problem observed in long- term storage was bitter pit (blotch pit). However, a new disorder we refer to as "stain" was also found during the second part of the past storage season in lots stored in CA. We evaluated numerous lots from warehouses in the Yakima, Washington, area for stain incidence starting in January, after receiving several samples from across the state with similar symptoms. The following general characteristics were determined for this disorder: —Its color may vary from a clear, greenish color to dark brown. —It commonly appears on the sun-exposed side of the fruit as diffuse spots of varying size (up to 2 inches in diameter), especially on apples with green or breaking background color (Figure 1).The stains do not typically become worse when fruit is held in cold storage or at room temperature. —The shape of the stains is irregular, from undefined areas to a droplike appearance (Figure 2). —Drops can be mistakenly identified as car- nauba staining. However, the disorder was com- monly found in the bins before packing, and secondly, we observed samples under ultraviolet light and no wax residue was found across the damaged areas. The disorder is not correlated to percentage of red skin color or fruit size (Figure 3). Cause So far, we have very limited information about the cause of this disorder. While some initial reports claimed that the stains appeared more often after the fruit was run over the packing line, this problem was found a few weeks later on apples in bins com- ing out of CA storage. Since the identification of the disorder is easier when the apples are waxed, it is possible that the first batches of fruit with stains coming from bins were missed (Figure 4). All samples observed were treated with Smart- Fresh (1-methylcyclopropene, MCP). We currently do not believe it was the cause of this disorder, but we cannot exclude that it contributed to the occur- rence of the disorder. The stains only affect the skin of the fruit and are not related to any other disorder such as soggy breakdown, cavities, or internal browning (Figure 5). Similarly, the characteristic Honeycrisp flavor remained the same despite the presence of the stains. Once packers were aware of the problem, affected fruit was downgraded during packing or packed boxes were repacked. However, we did find stained fruit in supermarkets in Yakima along with good fruit. www.goodfruit.com GOOD FRUIT GROWER AUGUST 2012 17 Common symptoms of stain. There is no correlation between apple size and presence of the stains. Fruit with staining in bins coming out of CA storage. The stain does not penetrate into the flesh of the fruit. In conclusion, we believe the disorder likely was initi- ated in the field. Efforts are under way to review spray records to determine possible preharvest aggravators or causal agents. • Figure 1 Figure 3 Shape and color of the stains can be variable. Figure 4 Figure 5 Harvest/Postharvest Figure 2a Figure 2b PHOTOS COURTESY OF INES HANRAHAN, WASHINGTON TREE FRUIT RESEARCH COMMISSION

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