Effect of Kasugamycin on Fire Blight during the Flowering Stage of Apple in Korea

Since fire blight was first discovered in Korea in 2015 on pears and apples, the agrochemicals containing streptomycin, oxolinic acid, and oxytetracycline as the main agents have been used as fire blight control agents. Since these antibiotics can easily produce resistant bacteria, the efficacy of kasugamycin soluble liquid (SL), which is not yet registered in Korea, against fire blight in apples during the flowering period was verified to supplement these agents. This test was conducted in 2024 and 2025 in an isolation facility built and operated by the Rural Development Administration in accordance with the Living Modified Organisms Safety Management Regulations. In 2024, when the Fuji variety was treated with 1,000-fold and 500-fold diluted kasugamycin SL, the control effects were 85.7% and 93.7%, respectively, which were comparable to the control effects of 90.8% of the 2,000-fold dilution of streptomycin wettable powder (WP). In 2025, when treating the Easypple and Hongro varieties with a 1,000-fold dilution of kasugamycin SL, it showed a control effect comparable to that of streptomycin WP. Therefore, kasugamycin SL is recommended as a new fire blight control agent in Korea.