Strawberry crown rot management: comprehensive analysis of Colletotrichum diversity, fungicide sensitivity and field efficacy assessment

BACKGROUND Strawberry crown rot, caused by Colletotrichum species, poses a significant challenge in strawberry production. Current management strategies are often ineffective owing to the complex diversity of the causal pathogens. Hence, it is important to accurately identify Colletotrichum species and select effective fungicides accordingly. RESULTS Strawberry crown rot in strawberry fields in Shandong Province is caused primarily by C. siamense , followed by C. fructicola and C . pandanicola . Compared with C. fructicola and C . pandanicola , C. siamense showed good adaptability and pathogenicity. In vitro tests revealed that fluazinam and fludioxonil had relatively high activity. Interestingly, C. siamense (CMCM0540) was insensitive to benzovindiflupyr with a mean half maximal effective concentration (EC 50 ) of 17.26 ± 2.01 mg L −1 . To understand the reason for this insensitivity, the succinate dehydrogenase subunit B ( sdh B), sdh C and sdh D gene sequences were analyzed. However, no known mutations reported to cause resistance were found compared with XM_036632635.1, XM_036637610.1, and XM_036642880.1 (from C. siamense ), suggesting that other mechanisms, rather than target‐site changes, may be responsible. The field efficacy of fungicides on strawberry crown rot and daughter plant yield were evaluated. Fludioxonil had the highest efficacy (77.88 ± 4.32%), followed by benzovindiflupyr (72.38 ± 7.35%). Benzovindiflupyr had the most significant positive effect on daughter plant yield. Therefore, fludioxonil and benzovindiflupyr can be employed as rotation fungicides for managing this disease. CONCLUSION This work identified the Colletotrichum species causing strawberry crown rot. Fludioxonil and benzovindiflupyr showed good efficacy against crown rot and have potential for disease management.