AbstractBACKGROUNDLaodelphax striatellus (Fallén) (Hemiptera: Delphacidae) is one of the most important insect pests of rice, and it has been able to develop strong resistance to many insecticides. Triflumezopyrim, a new type of mesoionic insecticide developed by Corteva Agriscience, showed high biological activity in controlling piercing‐sucking insect pests such as planthopper and leafhopper.RESULTSIn this study, we continuously selected a susceptible laboratory stain (Unsel) of L. striatellus for 16 generations by exposing it to triflumezopyrim in the laboratory. A 45.1‐fold triflumezopyrim‐resistant strain (Tri‐sel) was established, in which cross‐resistance to nitenpyram and acetamiprid was not detected. The realized heritability (h2) of the Tri‐sel strain was estimated at 0.13. The mortalities of the testing F1 (the offspring of a cross between Unsel and Tri‐sel strains) suggested that the resistance of L. striatellus to triflumezopyrim was autosomal and incompletely dominant, as well as a polygenic inheritance. In addition, the results of synergist experiment showed that P450s potentially contributed to the triflumezopyrim resistance. The activities of detoxification enzymes in the Unsel and Tri‐sel strains indicated that the activity of P450s in the Tri‐sel strain was significantly increased, consistent with the results of synergist experiments. Furthermore, 12 P450 genes demonstrated significant up‐regulation.CONCLUSIONSL. striatellus has a certain risk of resistance to triflumezopyrim after continuous selection. Triflumezopyrim resistance did not result in cross‐resistance to neonicotinoid insecticides. The up‐regulation of multiple P450 genes may mediate triflumezopyrim resistance in L. striatellus. © 2022 Society of Chemical Industry.