Sunburn may occur in some horticultural crops such as apples, and can cause a lot of damages to fruit of most cultivars, especially red apples, such as Red Delicious cultivar. In the present research, the effect of different treatments of kaolin (0.00, 2.50, 5.00, and 7.50%) was studied on the severity of sunburn on fruit of apple ‘Red Delicious’. Foliar spraying of kaolin was carried out in two times including early-June and early-July. The results of early-June spraying showed that the amount of sunburn on the fruits was affected by the treatments so that there were no significant differences between treatments of 2.50, 5.00, and 7.50% kaolin, but those treatments showed significant differences with the control (0.00). In addition, the results of early-July showed that the amount of sunburn on the fruits was affected by the kaolin treatments so that the highest amount of sunburn was observed in the control fruits and lowest sunburn was in the fruits treated with 7.50% kaolin. The treatments of 5.00 and 7.50% kaolin in both spraying times had the highest effect on reduction of fruit sunburn. It can be concluded the treatment of 7.50% kaolin in early-June and early-July is the best to reduce the sunburn on fruit of apple ‘Red Delicious’.
