Sunburn is a physiological disorder caused by excessive solar radiation; especially UV-B and excessive temperatures. There are three types of sunburn. Sunburn necrosis occurs when the fruit surface temperature (TPP) reaches 52 °C, sunburn browning occurs when TPP reaches 46-49 °C, and photo-oxidative sunburn occurs when the fruit is suddenly exposed to excessive sunlight. Although apples have special mechanisms to protect themselves, sunburn affects not only the outside of the fruit but also the inside - the content of dry matter, titratable acids, and firmness of the fruit changes. In addition to light and temperatures, factors including the choice of rootstock, cultivar and training system can also be used to mitigate sunburn. Semi-vigorous or vigorous rootstocks and less susceptible cultivars have a big impact on reducing this disorder. Technological measures that are the most effective and have had an impact on reducing the occurrence of sunburn are evaporative cooling (EC), which reduces the fruit temperature for 4,4-6,7 °C, fruit bagging, use of shade nets causes 5,4-9,7 °C lower temperatures and use of kaolin lowers temperatures of fruit for 1,5-6,4 °C. Among the growers, the most popular measures are the use of shade nets and kaolin, since hail nets, are a standard part of the technology, and kaolin is easy to use. In the future, these and additional measures will be used even more, due to increasingly frequent periods of hot and dry weather in our country as well.
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