Abstract:In order to understand the species of endophytic fungi in apple tree bark and their inhibitory effects on Valsa ceratosperma, endophytic fungi in 25 years Fuji symptomless apple bark were isolated and preliminary identified, and their inhibitory effects on V.ceratosperma were tested both through antibiotic test in Petri dish and protection test in the field. The 126 endophytic fungus strains were identified into 13 genera. Most species of endophytic fungi were isolated from bough. In the dual culture assays 24 endophytic fungus isolates showed inhibition rate above 40% and 87.5% of the isolates belong to Alternaria sp. The culture filtrate of Al 6 had better inhibition effect on the mycelial growth of V.ceratosperma, while Al 58 had better inhibition effect on conidia germination, with the inhibition rate of 83.76% and 82.42%, respectively. The volatile compounds produced by Al 67 had better inhibitory effect on the mycelial growth of V.ceratosperma, the inhibition rate reached 24.41%. The field test results showed that when the antagonistic endophytic fungi were firstly inoculated on apple tree, the followed infection and lesion extension of V.ceratosperma could be inhibited effectively. The most effective one was Al 107, which totally inhibited the infection of V.ceratosperma under the condition of artificial inoculation.