Influence of spinosad on reproduction of diamond back moth Plutella Xylostella (Linnaeus)

The diamond back moth, Plutella xylostella (Linnaeus) (Lepidoptera: Yponomeutidae), one of the most destructive insect pests of crucifers world over, demands evaluation and subsequent introduction of new molecules for its effective management. Spinosad, a naturalyte with mode of action different from conventional insecticides, was evaluated for its influence on various reproductive parameters of P. xylostella by treating the second instar larvae with various toxicity levels i.e. LC30 (0.00010%), LC50 (0.00057%) and LC70 (0.00327%). Significant reduction in oviposition period (3.27 days as compared to 7.6 days in the control), fecundity (17.80 as compared to 87.40 in the control), egg-size (0.84 x 10−2 mm3 as compared to 1.03 x 10−2 mm3 in the control), reproductive effort (0.17 as compared to 0.90 in the control), egg hatchability (72% as compared to 92% in the control) and survival of newly emerged larvae (70% as compared to 90% in the control) was registered under the influence of spinosad. SEM studies revealed deformations of ovarian follicles of the spinosad treated females; the ovarian follicles appeared somewhat rounded/oval (length decreased and breadth increased) in comparison to elongated ones in the control. The changes in shape, appearance and size of follicles in treated females as compared to control indicated that spinosad may have considerable effect on development of ovarioles, thereby signifying no sign of induction of resurgence. Given to its efficacy and safety to mammals and other non-target organism, spinosad can prove to be a viable insecticide for management of P. xylostella given to its promising efficacy subjected to successful results in the field.