Abstract:The effect and control efficacy of 7 strains of endophytic actinomycetes on Valsa ceratosperma, the pathogen of apple tree valsa canker, were tested by conidial germination, mycelial growth as well as twigs lesion control in excised twigs and in field trial. The inhibition rates of 7 strains of endophytic actinomycetes on conidia germination were more than 85% after treated with 2 times dilution of cell-free fermentation liquid. The inhibition rates on mycelial growth were more than 80% after treated with 20 times dilution of cell-free fermentation liquid. It was found that the germ tubes and mycelium of V.ceratosperma exhibited obvious malformation after treated with the cell-free fermentation liquid of Hhs.015 (BAR1-5) strain. After spreading the wound with the cell-free fermentation liquid of the 7 stains of endophytic actinomycetes and inoculating the mycelia cake on excised twigs, development of lesions were inhibited remarkably 5d later. The control efficiency of AR1-14, Hhs.015 and TGYXCSA-7 were 83.2%, 69.7% and 85.6%, respectively. In the field trails, the control efficiency in lesion recrudesce were more than 80% after spreading the fermentation liquids of actinomycete strains on the wounds.