Spinetoram, a spinosyn insecticide is used to manage lepidopteran pests, including diamondback moth, Plutella xylostella. In addition to determining the lethal effects, identifying low and/or sublethal effects of an insecticide is crucial to understanding the total impact of an insecticide. We assessed the low lethal and sublethal effects of spinetoram on two successive generations of P. xylostella. The initial bioassay results showed that spinetoram exhibited high toxicity against P. xylostella with an LC50 of 0.114 mg L-1 after 48 h exposure. The low lethal (LC25) and sublethal (LC10) concentrations of spinetoram showed significant reduction in pupation rate, pupal weight and adult emergence. The fecundity of F1 generation was significantly lower in LC25 (117.85 eggs/female) and LC10 (121.34 eggs/female) treated group than untreated control (145.32 eggs/female). The intrinsic rates of increase (r) was significantly lower (r = 0.1984 day-1) in spinetoram treated P. xylostella F1 progeny compared to untreated control (r = 0.2394 day-1). Our results suggest that LC10 and LC25 concentration of spinetoram might affect P. xylostella population growth by reducing its survival, development, and reproduction.
Keywords: Diamondback moth; Resistance management; Spinosyns; Sublethal effect; Toxicity.