As global warming progresses, sunburn damage in fruit production is becoming increasingly prevalent. However, there has not been much research on the patterns of sunburn occurrence and effective prevention measures for ‘Fuyu’ sweet persimmons. This pilot study explored the impact of strong light and high temperatures on sunburn occurrence in ‘Fuyu’ sweet persimmons, characterized the temporal pattern of sunburn development, and evaluated the efficacy of chemical suppressants in reducing damage. ‘Fuyu’ persimmons were harvested from an orchard in Jinju-si, Gyeongsangnam-do, South Korea, at 60 days (weak light intensity (WLI) conditions), 72 days (strong light intensity I (SLI-I) conditions), and 79 days (strong light intensity II (SLI-II) conditions) after full bloom. The harvested fruits were divided into five treatment groups: control (Distilled water), 2% Cellulose Nano Crystals (CNCs), 2% Sodium Alginate 300mM CaCl2 (AG), 6% Kaolin 0.1% Tween20 (K), and 2% Vapor Gard® (VG, transpiration inhibitor). Thermocouples were attached to each fruit to measure fruit surface temperature (FST) under the following conditions: WLI (using a chamber set to 200 µmol/m²/s light intensity) and SLI-I, -II (direct sunlight and temperature) conditions. When exposed to WLI conditions, the increase in fruit surface temperatures (FST) compared to air temperatures (AT) was minimal, and no sunburn was observed. Conversely, non-acclimated fruits exposed to SLI-I displayed extensive sunburn damage within a day. However, acclimated fruits under SLI-II revealed differences in sunburn. The kaolin treatment, which exhibited the lowest browning, also showed a significant reduction in FST. However, the carotenoid content was lower in the kaolin treatment compared to the control. To confirm the findings from controlled experiments, field trials were conducted for two years to evaluate the effectiveness of sunburn suppressants. In the first year, kaolin treatment reduced the severity of sunburn by half compared to other chemical suppressants. In the second year, 6% kaolin and a mixture of kaolin and carnauba wax were applied. Both kaolin and a kaolin-carnauba wax mixture effectively reduced sunburn to 30% of the control. These effective treatments decreased FST by up to 3.5℃, maintained high chlorophyll content, and augmented antioxidant enzyme activities. In conclusion, the kaolin treatment combined with carnauba wax was identified as the most promising material for preventing sunburn damage in ‘Fuyu’ persimmons under these environmental circumstances.
