Grapes are one of the world’s largest fruit crops and are widely cultivated in Iran. Sunburn is one of the major problems involved in the cultivation and exploitation of this fruit crop, which leads to a decrease in the apparent quality of the fruit and a sharp drop in marketability, reduced yields, and problems with its export. Therefore, to provide solutions to reduce these problems, the present study was conducted with foliar application of kaolin in four concentrations (0.00, 2.50, 5.00, and 7.50%) for two times including mid-June and mid-July, on ‘Thompson Seedless’ grapevine cultivar. The results showed that the sunburn on the berries and leaves was lower in the treated vines than untreated vines, and the best result was achieved with kaolin used in mid-June, which could completely control leaf sunburn. The result also showed that kaolin had a positive effect on bunch length, bunch weight, bunch density, berry length and berry width. Therefore, it is suggested that foliar application of kaolin is a suitable, affordable and inexpensive solution to reduce the damages caused by sunburn in leaves and fruits, especially in areas where the intensity of the sun is high. Due to the fact that there were no sunburns in leaves treated by kaolin in mid-June, it is recommended that the solution may be applied in mid-June.
