Side Effects of Sublethal Concentration of Two Neonicotinoids; Thiamethoxam and Thiacloprid on the Larval Parasitoid, Bracon brevicornis (Hymenoptera: Braconidae)

Abstract

Aims: To assess the responses of the larval parasitoid Bracon brevicornis, exposed as larvae parasitized on Spodoptera littoralis larvae, to two neonicotinoids. Study Design: The immature and adults stages of the larval parasitoid B. brevicornis were investigated on the treated 2nd larvae instars of Spodoptera littoralis at periods zero time, 1st, 3rd and 5th days of parasitism by these two neonicotinoids with contact method. Place and Duration of Study: A laboratory experiments were carried out during the summer 2013 at Faculty of Agriculture, Cairo University, Egypt. Methodology: Two neonicotinoids including thiacloprid and thiamethoxam at sublethal dose under constant laboratory conditions by spray method (direct toxicity) to the parasitoid adults and by contact method (indirect toxicity) on the parasitoid, B. brevicornis for five minutes to the 2nd larval instars of S. littoralisas as a host at zero time, 1st, 3rd and 5th days of parasitism. Results: No significant difference was found between the two tested compounds on larval and pupal durations. thiacloprid have higher toxic effect than thiamethoxam on the larval parasitoid, B. brevicornis. Thiacloprid achieved low number of emerged adults /parasitoid's female, low emerged females, shorter male and female longevity. Conclusion: Using of thiamethoxam for controlling sucking insect pests is more safer for the larval parasitoid, B. brevicornis than thiacloprid. We also suggest that thiamethoxam share programs of integrated pest management.