Activity of the Antioxidant Defense System in a Typical Bioinsecticide-and Synthetic Insecticide-treated Cowpea Storage Beetle Callosobrochus maculatus F. (Coleoptera: Chrysomelidae)

The non-enzymatic and enzymatic antioxidant defense systems play a major role in detoxification of pro-oxidant endobiotics and xenobiotics. The possible involvement of beetle non-enzymatic [α-tocopherol, glutathione (GSH), and ascorbic acid] and enzymatic [catalase (CAT), superoxide dismutase (SOD), peroxidase (POX), and polyphenol oxidase (PPO)] antioxidant defense system on the insecticidal activity of synthetic insecticides (cypermethrin, 2,2-dicholorovinyl dimethyl phosphate, and λ-cyhalothrin) and ethanolic plant extracts of Tithonia diversifolia, Cyperus rotundus, Hyptis suaveolens leaves, and Jatropha Curcas seeds was investigated. 2,2-Dicholorovinyl dimethyl phosphate (DDVP; 200 ppm, LC₅₀ = 13.24 ppm) and T. diversifolia (20,000 ppm) resulted in 100% beetle mortality at 96-hour post-treatment. The post-treatments significantly increased the beetle α-tocopherol and GSH contents. Activities of CAT, SOD, POX, and PPO were modulated by the synthetic insecticides and bioinsecticides to diminish the adverse effect of the chemical stresses. Quantitative and qualitative allelochemical compositions of bioinsecticides and chemical structure of synthetic insecticides possibly account and for modulation of their respective enzyme activities. Altogether, oxidative stress was enormous enough to cause maladaptation in insects. This study established that oxidative imbalance created could be the molecular basis of the efficacy of both insecticides and bio-insecticides. Two, there was development of functional but inadequate antioxidant defense mechanism in the beetle.