Combined effects of Azadirachtin and Citrus limonum essential oil against Sitophilus granarius: Toxicity and Biological Activities

Results on the fumigant and repellent potency of azadirachtin (1%) and Citrus limonum essential oil 50:50 v/v (Aza-EO), applied simultaneously against the major stored grain pest Sitophilus granarius (L.), direct (mean mortality) and delayed effects on selected biomarkers catalase (CAT), glutathione S-transferase (GST) and glutathione (GSH) as well as on the main biochemical constituents (proteins, lipids, carbohydrates and their nutritional depletion index (NDI)) and synergism between Aza and EO are reported. Combination persistence was also investigated while seeking a possible synergistic effect. Aza-EO exhibited insecticidal activity against S. granarius with a significant repellence. Surviving treated adults (LC₂₅ and LC₅₀) showed an induction of detoxification enzyme activities of CAT and GST accompanied by a decrease in GSH rate. The tested combination affected the energy reserves with the strongest effect on protein and lipid contents. The synergitic ratios suggest a significant synergistic interaction between the two mix camponents.