Sang-Jin Yang

Influence of Air Temperature during Midsummer on Fruit Sunburn Occurrence in 'Fuji'/M.9 Apple Tree

This study was carried out to investigate the effects of air temperature during midsummer on sunburn occurrence that had some problems recently on `Fuji`/M.9 planting system in Korea. There was a positive relationship between sunburn incidence and accumulated days with high air temperature over , or accumulated total quantum per day. `Fuji`/M.9 apple trees with relatively open canopies, compared to `Fuji`/M.26, were more susceptible to sunburn injury because the fruit was more exposed to sunlight. In `Fuji`/M.9 apple trees, those that were poor in vigor or with short bourse shoot length were more susceptible to sunburn injury. Sunburn incidence was affected by neither regions nor row orientations. Sunburn was observed most often on the fruits on the south and west sides of the trees. The reason was due to high skin temperature of the fruits reaching under full sunlight.

Effects of Microspraying of Water and Coating by White Materials on Fruit Sunburn Occurrence for `Fuji`/M.9 Apple Tree

This study was carried out to compare and analyze control methods of the sunburn occurrence that affected `Fuji`/M.9 planting systems in Korea from 2001 to 2003. It is very important to control temperature of the surface of fruits, because sunburn may occur when the temperature of fruit surfaces reaches due to high air temperature and sunlight during growing periods. As control methods of the sunburn occurrence, white coating materials such as or kaolin were applied four times at two-week intervals from late June, and microspraying of water was conducted when air temperature was over from late July to mid-August. Both methods were effective for preventing the sunburn occurrence and improving fruit quality by decreasing peel`s temperature of fruits and increasing photosynthesis.