Abstract： [Objectives]To investigate the resistance of Panonychus ulmi Koch to commonly used acaricides in apple orchards in Shaanxi province,China.[Methods]The susceptibility baseline of a laboratory susceptible strain to five commonly used acaricides was determined using the slide-dipping method.The relative resistance of P.ulmi from nine regions in Shaanxi province was monitored in 2021 and 2022.[Results]P.ulmi populations have developed a low level of resistance to abamectin relative to the susceptible strain.The Fufeng population had the highest resistance ratio(9.78 fold)to abamectin,so the use of this acaricide should be restricted in Fufeng.All populations had low to moderate resistance to pyridaben,with resistance ratios of 1.53-17.99.The Liquan population had the highest resistance to pyridaben,so pyridaben should be discontinued in Liquan.Resistance to azocyclotin and spirodiclofen were low to moderate,resistance ratios for each being 1.07-12.11 and 3.66-22.09,respectively.The use of azocyclotin and spirodiclofen should be discontinued in Liquan and Fufeng.Fengxiang and Fufeng populations have developed moderate resistance to bifenazate,consequently,this chemical should no longer be used in these regions.[Conclusion]The use of abamectin,spirodiclofen and bifenazate for the control of P.ulmi should be suspended,or restricted,in the Fufeng area,Pyridaben and azocyclotin should no longer be used in the Liquan area.To delay the development of further resistance,abamectin and bifenazide should be used in rotation in all regions except Fufeng and Liquan.