Biological Characterization and Fungicide Sensitivity of Dactylobotrys graminicola Causing Oat Spikelet Rot in China

Oat (Avena sativa) is a significant cereal crop that is extensively cultivated in temperate regions and is suitable for growth at higher elevations. The damage degree and epidemic area of oat spikelet rot caused by Dactylobotrys graminicola are generally increasing and spreading. Mycelium growth rate method was used to identify biological characteristics and in vitro fungicide screenings of D. graminicola. The results show that sorbitol and casein tryptone were the best carbon and nitrogen source for the D. graminicola, respectively. The optimal temperature for mycelium growth and conidia production of the D. graminicola was 20 °C; meanwhile, an acidic environment was shown to be conducive to mycelia growth, and alkaline facilitated conidia production. Among the ten tested fungicides, 20% Pydiflumetofen showed the best inhibition rate, with an EC50 (concentration for 50% of maximal effect) value of 0.005 mg/L; 30% Difenoconazole Propiconazole and 35% Metalaxyl-M Fludioxonil also showed sufficient inhibitory effects against D. graminicola, with EC50 value of 0.05 mg/L and 0.04 mg/L. Furthermore, we used artificial inoculation to determine the effectiveness of fungicide control in field, Trifloxystrobin 10%-Tebuconazole 20% with more than 90% control effectiveness, followed by 20% Pydiflumetofen. The results of this study not only revealed the biological characteristics of D. graminicola, but also provided effective candidate fungicides for the prevention and control of oat spikelet rot disease.