Identification of Pathogens Causing Foxtail Millet Blast and Screening of Chemical Fungicides and Biocontrol Bacteria

Foxtail millet is one of the important minor cereal crops and is highly valued for its nutritional quality and drought tolerance. With the continuous expansion of the foxtail millet industry, the harm caused by foxtail millet blast has become increasingly severe. In this study, 53 samples of foxtail millet leaves symptomatic of foxtail millet blast were collected from a foxtail millet base in Dingxiang County, Shanxi Province, from June to October 2023. Isolation, culture and identification of the pathogen were carried out, yielding a total of 16 pure isolates, and preliminary studies on the growth inhibition and control effects of the fungus were conducted by determining the plate inhibition rate, scanning electron microscope observations and indoor potted plant experiments. The results showed that based on the morphological characteristics of the isolated strains and the combined analysis of ITS-RPB1-ACT sequences, all 16 pure isolates obtained were identified as Pyricularia oryzae. The results of the antifungal test showed that Bacillus velezensis YQH had the highest inhibition rate of 57.93% against the pathogen of foxtail millet blast; among chemical fungicides, 9% Pyraclostrobin Suspension Concentrate, 45% Prochloraz Emulsifiable Concentrate and 32.5% Difenoconazole–Azoxystrobin Suspension Concentrate had strong inhibitory effects on the fungus, with EC50 values (95% confidence intervals) of 0.328 (0.262–0.400) μg·mL−1, 0.848 (0.578–1.219) μg·mL−1 and 0.310 (0.197–0.484) μg·mL−1, respectively. The results of the potted plant experiment were in accordance with the in vitro antifungal results, and scanning electron microscopy showed that the mycelia in the treatment groups of these three chemical fungicides showed developmental deformities, breakage or surface shrinkage. In conclusion, B. velezensis YQH and the three chemical fungicides (especially 9% Pyraclostrobin Suspension Concentrate and 32.5% Difenoconazole–Azoxystrobin Suspension Concentrate) are effective candidates for controlling foxtail millet blast.