The Asian citrus psyllid, Diaphorina citri (Kuwayama) (Hemiptera: Liviidae), is a severe pest of citrus orchards worldwide. Its control is based mainly on the use of conventional insecticides, and resistance to many of those compounds is widespread. Phenotypic bioassays to detect resistance compare the response of a field-collected population with a laboratory-reared population that is susceptible to insecticides. This comparison usually does not involve a susceptible field-collected counterpart since its existence is currently rare. We found an isolated field population of D. citri living on a wild host, orange jasmine (Murraya paniculata [L.] Jack). Considering its lifetime fly capacity, gene flow with any insecticide-treated population was nonexistent or negligible. Thus, we determined the response in fourth-instar nymphs and unsexed 2- to 5-d-old adults in bioassays of commercial formulations of the commonly used insecticides chlorpyrifos, malathion, imidacloprid, and spinosad. In the bioassays, insects were placed on leaf discs previously immersed for 10 s in the respective insecticide concentrations. For adults, the lowest concentration–mortality response was with chlorpyrifos (lethal concentration 50 [LC₅₀] of 0.72 mg L^-1 and lethal concentration 95 [LC₉₅] of 1.02 mg L^-1). The highest toxicity response was with malathion (LC₉₅ of 0.05 mg L^-1). The highest toxicity response with fourth-instar nymphs was observed with spinosad (LC₅₀ of 0.007, LC₉₅ of 0.021 mg L^-1). The estimated LC₅₀ and LC₉₅ values for chlorpyrifos, malathion, and spinosad were lower than those documented worldwide for these insecticides in susceptible populations of D. citri.