Objective To investigate and analyze leaf scorch of Castanea mollissima occurred in the main chestnut producing areas in Hebei Province.

Method Combined the investigation of the symptoms in the forest, the isolation of microbes from the symptomatic leaf tissue, the confirmation of Koch's law in vitro leaves and potted seedlings, with the management measures of orchard and the environmental factors, the causes of disease were analyzed and discussed.

Result The disease rate of orchard trees was 20%–50%, the disease rate of individual tree leaves can be up to 100%, the main symptom of individual leaf was dry leaf margin and interveinal tissue. No pathogen was found in the forest symptomatic tissues and microscopic examination. A total of 102 strains were isolated and purified from symptomatic tissues, all of which were fungi, belonging to 10 families, 12 genera and 15 species with Alternaria alternata as the most abundant. The inoculation test showed that Ophiognomonia setacea and Coniothyrium pyrinum could induce the browning of leaf tissue of Chinese chestnut. However, the symptom was significantly different from that of chestnut forest leaf scorch.

Conclusion Two pathogens, O. setacea and Coniothyrium Pyrinum, were newly found and verified to be pathogenic to Chinese chestnut leaves, causing chestnut tree leaf spots, which were different with the leaf scorch symptoms in chestnut observed. Currently, leaf scorches in trees are ordinarily connected with environmental and physical factors which influenced tree growth with global warming, extreme weather, pollution, inadequate silviculture and control pests/diseases managements. Therefore, integrating non-infection to investigate causes of the leaf scorch of Castanea mollissima occurred in Hebei Province is strongly proposed in order to effectively prevent and control the disease as soon as possible.