Abstract:

In order to study insecticidal activity of spinosad against Lymantria dispar, bioactivity and LC₅₀ of spinosad against the 3rd and 5th instar larva of L. dispar and its effect on activities of the detoxifying enzymes were assayed in this study. The results showed that LC₅₀ of spinosad in 24 h was 0.0249 mg·L^-1 against 3rd instar larva and 0.2269mg ·L^-1 against 5th instar larva. Spinosad had various effects on activities of the detoxifying enzymes under the LC₅₀ treatment. Carboxylesterase (CarE), glutathione-S-transferase (GST), multi-function oxidase (MFO) and alkaline phosphatase (ALP) were firstly significantly increased and then decreased (P <0.05); But for acid phosphatase (ACP), the change pattern in activity were decreased-increased-decreased, and the variation was significant (P< 0.01). The development duration of the larva treated with LC₁₀ and LC₅₀ of spinosad was not significantly different from control, but the larval survival rate and pupation rate were significantly lower than control (P<0.05). The result indicated that the biochemical indexes of L. dispar were affected by spinosad. Therefore, spinosad is a safe and effective pesticide for L. dispar.

Key words: spinosad, Lymantria dispar, detoxifying enzymes