Biological characteristics and fungicide sensitivity of Pyricularia variabilis

In recent years, the pathogen that causes leaf blast on Amomum tsao-ko repeatedly infected the plants in a large area of Luchun County, Honghe Prefecture, Yunnan Province, China. The disease is caused by the pathogen Pyricularia variabilis. The effects of light, temperature, pH, carbon, and nitrogen sources on the growth of the pathogen were determined, and its sensitivity to six fungicides was determined using the mycelial growth rate method. The optimal conditions for mycelial growth were as follows: temperature: 20-25°C; carbon source: maltose, nitrogen source beef extract, media corn flour, and potato dextrose agar. The mycelia could grow under four types of light conditions: 24 h light, 24 h dark, 12 h light/12 h dark, and 16 h light/8 h dark. In addition, Propiconazole was the most effective inhibitor, with an EC₅₀ value of 0.030 μg/mL, and prochloraz was the second most effective, with an EC₅₀ value of 0.076 μg/mL. It is suggested that the two fungicides should be alternated when used in production. Carbendazim and chlorothalonil were ineffective in inhibiting the fungus, with EC₅₀ values of 6.137 and 3.765 μg/mL, respectively.