Identification, Distribution, and Fungicide Sensitivity of Colletotrichum spp. Causing Peach Anthracnose in South Korea

Peach anthracnose, caused by Colletotrichum spp., poses a significant threat to peach production globally, including in South Korea. This study investigated the diversity, distribution, and fungicide sensitivity of Colletotrichum isolates from 15 commercial peach orchards across five regions in South Korea. A total of 256 isolates were obtained from infected fruits and identified through multilocus phylogenetic analysis as belonging to five species: C. fioriniae and C. nymphaeae from the C. acutatum species complex, and C. fructicola, C. siamense, and C. gloeosporioides from the C. gloeosporioides species complex, with C. fioriniae being the dominant species. The distribution of Colletotrichum species varied significantly across peach-growing regions in South Korea, with notable regional differences in disease incidence and fungicide resistance levels. To assess fungicide sensitivity, the isolates were tested against five fungicides: pyraclostrobin, thiophanate-methyl, tebuconazole, fluazinam, and prochloraz-manganese. Strains within the C. gloeosporioides species complex exhibited diverse responses to pyraclostrobin and thiophanate-methyl, while all C. fioriniae strains displayed resistance or inherent tolerance to each fungicide. No resistance was observed to tebuconazole, fluazinam, or prochloraz-manganese. These findings highlight the emergence of resistance to commonly used fungicides such as pyraclostrobin and thiophanate-methyl in Colletotrichum populations, emphasizing the need for alternative fungicides. This study provides valuable insights into the current status of peach anthracnose in South Korea and underscores the importance of continuous monitoring and disease management for sustainable control.