A study on the effectiveness of bio-medicaments in controlling oat leaf spot

In order to determine the effectiveness of biocontrol agents against oat leaf spot, four biocontrol agents were tested, and two chemical fungicides were used as controls for the control of naturally occurring oat leaf spot in Shandan County, Gansu Province. The results showed that 7 days after the first application, the control effect of the biocontrol agent (56.81%～63.59%) was generally lower than that of the chemical fungicides, 25% pyraclostrobin suspension (71.11%) and 43% tebuconazole suspension (73.60%). Seven days after the second application, the control effect of the test agents was greater than that of 7 days after the first application. Among the agents tested, the control effect of Trichoderma harzianum increased by 27.39% compared with the first application, which was the largest increase. Twenty days after the second application, the control effect of each agent was lower than that of 7 days after the second application. However, the control effect of biocontrol agents decreased slightly while the chemical fungicides decreased significantly. Bacillus subtilis had the highest control effect at 80.34%. In addition, treatment with 1 × 10¹¹ cfu·g⁻¹ Bacillus subtilis significantly increased the relative content of oat flag leaf chlorophyll, thousand-grain weight and seed yield (P < 0.05), and the three indexes increased by 26.13%, 13.22%, and 13.09%, respectively, compared with the control. Considering the comprehensive control effect, sustained effect, oat seed yield, and other indicators, the microbial source fungicide 1 × 10 ¹¹ cfu·g⁻¹ Bacillus subtilis is the best agent for preventing and controlling oat leaf spot. Spraying should be started at the beginning of the disease, with a second spraying after 7 days. In addition to controlling leaf spot disease, this agent can also increase seed yield by increasing the relative content of chlorophyll and 1 000-seed weight of oat flag leaves.