Abstract: In order to address the problem of Internal bark necrosis(IBN) induced by high Mn content in Liaoning province,experiments involving simultaneous applications of Mn and Si were conducted on one year old virus-free Fuji apple trees.Further experiments using Si to correct IBN after its symptoms appearing on leaves and branches induced by earlier single Mn applications were also conducted.The results showed that the simultaneous application of Mn and Si both with the dosage of 400 mg/kg could effectively prevent Fuji trees from developing IBN. Application of Si at 400(mg/kg) could control the development of IBN in leaves and reduce the symptoms in branches previously induced by application of Mn at 400 mg/kg.However,the effect on branches was less obvious than that in leaves.With increasing application of Mn,soil extractable K and Ca increased,while extractable Fe and Zn decreased in soil,which indicated that the(incidence) of IBN may be also related to captioned nutritional levels in soil.