Pathogen identification and fungicide screening of Sugarcane White Rash Disease in China

Sugarcane is the most important sugar crop in China. In recent years, a disease characterized by white rash symptoms has become endemic in sugarcane fields in the coastal area of Guangxi Province, China. A fungal species was consistently isolated from diseased leaves of sugarcane plants, and the pathogenicity assays were consistent with its etiology, reproducing symptoms identical to those observed in the field. Based on host range, symptomatology, and morphological characteristics, the causative agent was identified as Elsinoë sacchari. The fungus grew fastest on potato dextrose agar (PDA) at pH 6.0 and 25 °C, and grew well in a medium with oat as the carbon source or ammonium sulfate as the nitrogen source. In vitro fungicide sensitivity assays identified Difenoconazole as the potent compound for inhibiting mycelial growth and Pyraclostrobin·boscalid as the potent compound for inhibiting spore germination. Field trials showed that application of 75% Trifloxystrobin·tebuconazole at 0.250 g/L resulted in the lowest disease severity, while application of 38% Pyraclostrobin·boscalid at 0.190 g/L or 75% Trifloxystrobin·tebuconazole at 0.250 g/L yielded the highest cane production. This study clarified the key biological characteristics of E. sacchari and successfully screened several fungicides suitable for field control of Sugarcane White Rash Disease.