Biocontrol Efficacy of Lyophilized Powder and Culture Suspension Formulations of Streptomyces blastmyceticus Against Dryadomyces quercus-mongolicae Causing Oak Wilt Disease in Mongolian Oak

Oak trees are widely distributed nationwide and account for approximately 24% of the total forest area in South Korea. However, these species are currently threatened by oak wilt disease caused by Dryadomyces quercus-mongolicae, leading to significant economic and ecological losses in the forestry industry. This study evaluated the effectiveness of culture suspension and lyophilized powder formulations of Streptomyces blastmyceticus in controlling oak wilt disease on Mongolian oak (Quercus mongolica). Field experiments were conducted using trunk and root injection methods in Q. mongolica plantations. The non-conductive area (NCA) of sapwood and colonization rate of the oak wilt fungus were analyzed and compared across treatments. In the Chuncheon experiment, Kangwon province, only the root injection of fungicide showed a significant difference compared to the culture suspension treatments. There were no significant differences between culture suspension and lyophilized powder treatments in Uiwang, Gyeonggi Province. Specifically, both preventive and curative treatments using culture suspension and lyophilized powder of S. blastmyceticus resulted in significantly different NCA values compared to the negative control (8.7%) and positive control (88.5%). The NCA for culture suspension ranged from 33.3% to 49.9%, and for lyophilized powder, from 37.3% to 43.9%. The colonization rate of the oak wilt fungus was lowest (9.72%) in the preventive treatment using lyophilized powder via trunk injection. For the culture suspension, the lowest colonization rate (20.83%) was observed in the curative treatment using trunk injection. These findings suggest that the lyophilized powder formulation of S. blastmyceticus efficiently suppresses the progression of oak wilt disease under field conditions.