Sunburn 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 symptoms.

However, a series of field observations and numerous investigations led us to conclude that sunburn in apples, under Chilean conditions, is caused mainly by elevated temperature rather than by the influence of UV radiation.

The fact that the problem has become more acute in Chile in the last 20 years could be due to three factors: the incorporation of more susceptible cultivars; increasing use of dwarfing rootstocks; and more exposed training systems, such as Solaxe. The increase in ambient temperature in recent years is another factor to be considered.

Source - http://www.freshplaza.com/