Advancing Effect of Bacillus sp. Densities on the Suppression of Blast in Rice Caused by Pyricularia oryzae

Rice blast, caused by Pyricularia oryzae, is an important disease that can reduce rice productivity. This study evaluated the antagonistic ability of Bacillus sp. isolate D28 against P. oryzae and determined the effective bacterial population density for suppressing blast disease and promoting rice growth. The study was conducted from March to June 2026 at the Plant Health Laboratory and the greenhouse of UPT PATPH, East Java. A CRD was used with four treatments and six replications: B0 (control), B7 (Bacillus sp. at 10? CFU/mL), B8 (10? CFU/mL), and B9 (10? CFU/mL). We evaluated in vitro antagonistic activity using the dual-culture method, and assessed in vivo efficacy based on blast disease intensity, plant height, and leaf number. Bacillus sp. D28 inhibited P. oryzae, with inhibition zones of 5.00, 7.50, and 9.58 mm at 10?, 10?, and 10? CFU/mL, respectively. 10? and 10? showed significantly greater inhibition than 10? and the control but did not differ significantly from each other. In vivo, 10? and 10? reduced disease intensity to 11.11% and 10.41%, respectively, compared with 23.61% in the control at 28 days after inoculation. 10? showed the highest numerical efficacy (55.87%) and leaf number (40.33) at 49 days after sowing. Thus, Bacillus sp. D28 at 10? CFU/mL suppressed rice blast, while Bc9 showed the highest numerical growth response. Contribution to Sustainable Development Goals (SDGs):SDG 2: Zero HungerSDG 12: Responsible Consumption and Production SDG 15: Life on Land