Insecticidal effect of spinosad on larvae of Plutella xylostella L. (Lepidoptera: Plutellidae) under laboratory conditions

Due to economic importance of the diamondback moth and resistance to conventional insecticides, it is necessary to use novel and suitable compounds in control programs. Therefore, we evaluated the toxicity of Spinosad to four instars larvae of diamondback moth, Plutella xylostella (L.). In this study 1st, 2nd, 3rd and 4th instars larvae were exposed to different concentrations of Spinosad. The exposure times were 24, 48 and 72 h for oral trials. Experiments were performed in complete randomized block design with four replications. After treatment the samples were held under constant conditions in a laboratory rearing room (25 ± 2oC, 50 ± 5% RH and 14: 10 h L: D photoperiod). The maximum mortality rate for 1st, 2nd, 3rd and 4th instars larvae in 600, 700, 800 and 900 ppm of Spinosad was achieved 100, 95, 98.3 and 93.3% after 72 h, respectively. Our results suggest Spinosad could be an important agent in control of larval instars of Plutellaxylostell.   Key words: Bioassay, cabbage, Plutella xylostella, Spinosad