Toxicity testing of different fungicides for Colletotrichum cereale on oat anthracnose

Anthracnose caused by Colletotrichum cereale is the main limiting factor in the production of oats (Avena sativa) in the northern Shanxi Province; however, no research has been carried out on the prevention and control of oat anthracnose using chemical fungicides. To clarify the inhibitory effects of fungicides with different mechanisms of action on oat anthracnose, 10 fungicides from six categories were selected and studied, and their antifungal effects were measured using the hyphae growth rate method and the droplet method. The results showed that carbendazim (50% wettable powder, WP), propiconazole (50% WP), azoxystrobin (25% suspension concentrates, SC), and pyraclostrobin (25% SC) had strong inhibitory effects on the growth of C. cereale hyphae, with EC₅₀ (50% effective concentration) values of 0.0921, 0.8774, 0.1180, and 0.0029 mg·L⁻¹, respectively. Chlorothalonil (75% WP), carbendazim (50% WP), azoxystrobin (25% SC), and pyraclostrobin (25% SC) had a strong inhibitory effect on the germination of C. cereale spores. For chlorothalonil (75% WP), when the concentration was ≥ 0.80 mg·L⁻¹, the spore germination inhibition rate was 100%, and the EC₅₀ of carbendazim (50% WP), azoxystrobin (25% SC), and pyraclostrobin (25% SC) were 0.1124, 0.1184, and 0.0059 mg·L⁻¹. Based on the different mechanisms of action, it is recommended that chlorothalonil (75% WP) be used as a protective fungicide before anthracnose occurs, whereas carbendazim (50% WP), azoxystrobin (25% SC), and pyraclostrobin (25% SC) should be used as protective and therapeutic fungicides. In addition, producers should promptly rotate chemical fungicides with different mechanisms of action to prevent and control diseases, improve planting conditions, introduce and select disease-resistant varieties, and ensure the sustainable production of oats.