Isolation, Identification, and In Vitro Fungicide Screening of the Pathogen Associated with Pear Dry Blight

Pear (<i>Pyrus</i> spp.) is a globally important fruit crop, with China leading in the production and cultivation area. Pear dry blight, a destructive fungal disease, has emerged as a significant threat to pear orchards in Wuwei, Gansu Province, China. This study aimed to identify the causal pathogen, evaluate its pathogenicity, and assess the efficacy of commonly used fungicides. A total of 276 fungal isolates were obtained from symptomatic <i>Pyrus bretschneideri</i> stems and characterised through morphological and molecular analyses. <i>Diaporthe fukushii</i> was identified as the causal pathogen. Pathogenicity assays on Zaosu pear branches and Huangguan pear fruits resulted in 82% and 100% disease incidence, respectively, fulfilling Koch's postulates. In vitro fungicide evaluations demonstrated that thiophanate-methyl and difenoconazole + propiconazole exhibited the strongest inhibitory effects, followed by mancozeb, metalaxyl-mancozeb, and carbendazim, whereas chloroisobromine cyanuric acid and dimethomorph were the least effective. These findings are critical for developing effective management strategies to mitigate the impact of pear dry blight on pear production.