Synergistic effects of the combined application of Bacillus subtilis H158 and strobilurins for rice sheath blight control

Rice sheath blight, a major rice disease caused by Rhizoctonia solani, has become an increasingly serious problem in modern rice production systems. Managing this disease is a challenge, and chemical control with fungicides is currently the most effective and reliable method. Here, the combined application of a recognized biological agent, Bacillus subtilis strain H158, and strobilurins was tested for the ability to control rice sheath blight under laboratory, greenhouse, and paddy field conditions and achieved stronger control effects than strobilurins alone provided that the application rate of synthetic chemicals was not increased. Under culture conditions, B. subtilis H158 could tolerate high concentrations of strobilurins, and its growth was stimulated at low concentrations. The survival of H158 on rice leaves was not obviously inhibited by the strobilurins and was slightly stimulated at 10 days after application, especially when applied with trifloxystrobin. The combined application of H158 and strobilurins showed strong synergistic effects in the greenhouse and the field in two consecutive years. In these experiments, the combination of H158 and azoxystrobin showed the largest control effect, whereas H158 combined with trifloxystrobin displayed the strongest synergistic effect. B. subtilis H158 is compatible with strobilurins. The combined application of H158 and strobilurins effectively controlled rice sheath blight and showed strong synergistic effects. This combination could be an effective solution for rice sheath blight and an alternative to common chemical control methods to meet the growing demands to reduce chemical use in modern agriculture.