Toxicological Evaluation of Malathion and Deltamethrin Alone and Combined with Inert Carriers against Sitophilus granarius (L.) in Stored Wheat

This study evaluated the toxicity of chemical insecticides (malathion and deltamethrin) and natural materials (Diatomaceous Earth [DE] and Bentonite), individually and in combination, against Sitophilus granarius after 5 and 10 days of exposure. Results showed that chemical insecticides exhibited significantly higher toxicity than natural materials. Deltamethrin showed the highest toxicity (LC50 = 479.6 mg/kg after 5 days), while Bentonite displayed the lowest (LC50 = 3836.96 mg/kg). Combinations of insecticides with DE or Bentonite significantly enhanced toxicity, with deltamethrin + DE and malathion + DE combinations showed strong synergistic effects (SR > 2). Toxicity generally increased after 10 days of exposure, particularly for DE and Bentonite, reflecting their delayed mode of action. Additionally, treatments combining insecticides with inert materials achieved greater suppression of the F1 progeny compared to individual treatments. Germination tests revealed no significant adverse effects on seed viability when grains were treated with LC50 concentrations. Overall, combining chemical insecticides with inert materials like DE and Bentonite offers an effective strategy for enhancing pest control efficacy while preserving seed viability.