Good Fruit Grower

January 2015

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26 JANUARY 1, 2015 GOOD FRUIT GROWER S unburn is a serious problem that affects fruits and vegetables, particularly in areas of the world where an excess of solar radiation is combined with high temperatures. Sunburn can account for losses of up to 40 percent of the apple crop at the orchard, especially with cultivars such as Fuji, Braeburn, and Cripps Pink. In Chile, growers lose about 13.5 percent of their crop to sunburn, which amounts to more than U.S.$100 million in lost exports over the past several seasons. The Pomological Center (Centro de Pomáceas) at the University of Talca has been studying the problem of sunburn in apples since 1992. The initial hypothesis that guided our research was that UV (ultraviolet) radiation was responsible for the symp- toms. However, a series of field observations and numerous investigations led us to con- clude that sunburn in apples, under Chilean conditions, is caused mainly by elevated GOOD TO KNOW A research report from Dr. Jose Antonio Yuri, University of Talca, Chile. Sunburn in apples: A HOT PROBLEM Sunburn has been an increasing problem in Chile over the past 20 years. Figure 2 Sunburn damage in detached fruit can occur in a few hours, while fruit that remain attached to the tree do not present symptoms. Figure 1 Severe sunburn damage in apples, which occurs on the side of the fruit facing west or southwest, where the highest temperatures occur in the afternoon. b a Figure 3 Sunburn in bagged fruit. The symptoms appear on the side of fruit exposed to the sun, when the temperature of the peel exceeds a critical threshold. In this case there is no direct solar radiation. (Photos a and b)

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