Toxicological evaluation of insecticides on Bracon hebetor (Say, 1836) under controlled laboratory conditions

Abstract

Bracon hebetor (Say) is an eco-friendly and important biological control agent against numerous destructive insect pests worldwide. Its beneficial role is increasingly attracting the attention of growers seeking sustainable pest management solutions. However, some conventional and novel insecticides exhibit toxic effects on B. hebetor. The present study aimed to assess the toxicity of six commonly used synthetic insecticides, emamectin benzoate, acetamiprid, chlorpyrifos, imidacloprid, lufenuron, and flubendiamide, against the larval parasitoid B. hebetor under laboratory conditions (29 ± 1°C; 60 ± 5% RH). The experiment was conducted at the Toxicology Laboratory of the Entomological Research Institute, AARI, Faisalabad, Pakistan, using the vial residual method. Among the tested insecticides, chlorpyrifos was the most toxic to B. hebetor, with LC₅₀ values of 1901.16, 249.79, 81.13, 44.85, and 34.99 mg/L at 3, 6, 12, 24, and 48 h post-exposure, respectively. Acetamiprid and imidacloprid exhibited moderate toxicity, with LC₅₀ values of 31.75 mg/L and 223.95 mg/L at 48 h, respectively. In contrast, lufenuron showed lower toxicity (LC₅₀ = 877.87 mg/L at 48 h), while emamectin benzoate and flubendiamide were the least toxic, with LC₅₀ values of 580.28 mg/L and 2,325.36 mg/L, respectively. These findings indicate varying levels of toxicity among the tested insecticides, highlighting the need for careful selection of insecticides to minimize adverse effects on B. hebetor. To maintain ecological balance and promote biological pest control, insecticides with the lowest impact on B. hebetor should be used judiciously.