Diplocarpon mespilicola sp. nov. Associated with Entomosporium Leaf Spot on Hawthorn in China.

Entomosporium leaf spot (ELS) is a serious hawthorn disease that mainly causes premature leaf senescence in various hawthorn growing areas worldwide. Diplocarpon mespili is the most commonly reported pathogen causing hawthorn ELS. From 2016 to 2018, hawthorn ELS disease surveys and samplings were carried out in five regions in three provinces of China. The disease incidence was about 20 to 95%. A total of 186 single-spored Diplocarpon isolates were obtained and identified using morphological and molecular phylogenetic analysis. The results showed that all isolates clustered, suggesting a distinct species that is here proposed as D. mespilicola sp. nov. This is the first report of the pathogen causing ELS on hawthorn in China, and it is similar to the species D. mespili . To explore the influence of temperature on the epidemiology of D. mespilicola , we studied the continuous influence of temperature and time on the germination of conidia by using nine time points and eight temperature gradient observations. This study indicated that the optimum temperature for conidial germination was 20.4°C, and the minimum germination time was 4.9 h. Using this information to develop a predictive model may provide a basis for disease management in hawthorn production in the future.