Abstract: 【Aim】The aim of this study is to clarify the level of the field-evolved resistance of Tuta absoluta to spinetoram and its potential resistance risk, in order to provide a theoretical basis for the rational use of spinetoram to control T. absoluta and slowing development of its resistance to spinetoram. 【Methods】 The leaf-dipping method was used to determine the resistance levels of 18 field populations of T. absoluta collected from five provinces (municipalities or autonomous regions) in northern China to spinetoram. To assess the resistance risk of T. absoluta to spinetoram, 10-generation consecutive selections with spinetoram were carried out in the spinetoram-susceptible strain of T. absoluta via the leaf-dipping method. After that, the realized heritability (h²) of resistance was calculated using Tabashnik’s method for threhold trait agalysis, and the resistance development rates under different selection pressures were predicted based on the data of selection. 【Results】 Among the 18 field populations of T. absoluta, three populations including the populations from Miyun and Huairou in Beijing, and Baotou in Inner Mongolia, exhibited low-level resistance to spinetoram, with the resistance ratios of 6.7, 6.0 and 7.1, respectively. On the other hand, the other 15 populations of T. absoluta were susceptible to spinetoram. After 10-generation consecutive selections with spinetoram, T. absoluta developed 8.9-fold resistance to spinetoram, with the h2 of 0.1973. It was predicted that under different selection pressures (mortality=50%, 60%, 70%, 80% and 90%), T. absoluta needed 11.56, 9.50, 7.92, 6.60 and 5.23 generations, respectively, to develop 10-fold resistance to spinetoram, and 23.12, 18.99, 1583, 13.19 and 10.47 generations, respectively, to develop 100-fold resistance to spinetoram. 【Conclusion】 Due to the risk of T. absoluta developing resistance to spinetoram, it is essential to strengthen insecticide management in the field and emphasize the rotation with alternative types of insecticides to prolong the lifecycle of this insecticide.

Key words: Tuta absoluta, spinetoram, resistance monitoring, risk assessment, realized heritability