Leaf spot disease caused by Curvularia sp. poses a significant challenge during the oil palm seedling phase, often managed through preventive practices and fungicide application. However, the use of fungicides presents environmental hazards and may contribute to development of fungal resistance. This study investigates an alternative, a non-chemical approach using photon energy irradiation. In the first stage, Curvularia sp. was isolated at room temperature and exposed to red, green, and blue LED light with intensities of 1.25 mW/cm \(^{2}\) , 0.84 mW/cm \(^{2}\) , and 0.6 mW/cm \(^{2}\) , respectively, for 3 and 5 hours. Fungal growth was assessed over six days based on radial expansion on a petri dish medium. Results demonstrated that blue light exerted the strongest inhibitory effect on fungal growth, followed by green and red light. Microscopic analysis revealed a significant reduction in conidia density per unit area in blue light-treated samples compared to controls. In the next stage, four-month-old oil palm seedlings underwent pre-irradiation for 30 days using the same light treatments as in the first stage. Following this, the seedlings were inoculated with Curvularia sp. and subjected to either secondary irradiation or no additional treatment. Observations conducted 30 days post-inoculation indicated that blue light irradiation enhanced seedling resistance to Curvularia infection and effectively suppressed fungal in both irradiated and non-irradiated seedlings. The percentage quantification of fungal lesion spread, analyzed using the HSV (Hue, Saturation, Value) color space technique, demonstrated that blue light irradiation significantly suppressed leaf spot development. In non-pre-irradiated seedlings, leaf spots covered 3.18% of the leaf area, whereas in pre-irradiated seedlings, only 0.04% was affected. Red and green light irradiation also exhibited inhibitory effects on leaf spot growth, although slightly less effective than blue light. These findings suggest that light irradiation, particularly with blue wavelengths, is a promising alternative for managing fungal infections in oil palm seedlings while mitigating environmental and resistance-related concerns associated with chemical fungicides.
