Cross‐resistance, mode of inheritance, synergism, and fitness effects of cyantraniliprole resistance in Plutella xylostella

The diamondback moth, P lutella xylostella ( L .) ( L epidoptera: P lutellidae), has evolved resistance to various types of insecticides in the field. In the present study, the resistance of P . xylostella (designated Cya‐ SEL ) to cyantraniliprole increased to 30.6 and 326‐fold after 26 generations of selection, compared with the field population ( TA ) and susceptible population ( LAB ), respectively. The resistant population also had developed low to moderate levels of resistance to abamectin (3.3‐fold), flubendiamide (14.1‐fold), and chlorantraniliprole (24.3‐fold). Synergism tests indicated that piperonyl butoxide ( PBO ) and diethyl maleate ( DEM ) increased the toxicity of cyantraniliprole in the selected strain, i.e., synergism ratio was 2.8 and 3.3‐fold, respectively. Reciprocal crosses were made between the susceptible ( LAB ) and resistant strain collected from Zengcheng ( ZC ). The degree of dominance and overlapping confidence intervals of LC 50 values of F1 progenies ( ZC ♀ × LAB ♂ and LAB ♀ × ZC ♂) suggested an autosomal and incompletely recessive mode of resistance to cyantraniliprole. The test of monogenic inheritance based on a backcross of F1 progeny with the ZC population indicated that resistance to cyantraniliprole was controlled by multiple genes. Additionally, Cya‐ SEL had a lower reproductive ability and relative fitness than the other tested populations. These findings provide useful information for effective resistance management strategies against P . xylostella .