Bioinsecticide control and enzymatic responses in <i>Spodoptera frugiperda</i>

Spodoptera frugiperda (Lepidoptera: Noctuidae) is a serious invasive pest, which has attracted concern regarding the effectiveness of environmental bioinsecticide as a substitution for synthetic insecticide in controlling its damage to numerous agricultural crops in recent years. Hence, laboratory and field experiments have investigated insecticidal toxicity in S. frugiperda by 5 insecticides and have determined the activity of acetylcholinesterase (AChE) and detoxifying enzymes, namely mixed function oxidase (MFO), carboxylesterase (CarE), and glutathione S-transferase (GST) on 3rd instar larvae at 25% lethal concentration (LC₂₅) to explore detoxification mechanisms. The results showed that the most effective insecticides were 3.0% emamectin benzoate (0.024 mg/L), 60 g/L spinetoram (0.282 mg/L), and 1.3% matrine (0.380 mg/L) at 48 h depending on LC₅₀ values. The field efficiencies of emamectin benzoate and spinetoram were over 80% at 24 h and 90% at 72 h, indicating that both insecticides had acute and long-lasting toxicity on S. frugiperda; matrine had extended-release toxicity with 90% field efficiency at 72 h. Emamectin benzoate and spinetoram activated the activities of AChE, MFO and GST, and spinetoram decreased in CarE activity; cyantraniliprole induced an increase of 4 detoxifying enzymes; spinosad increased the activities of AChE, MFO, and CarE but not GST. Furthermore, matrine had an inhibiting effect on AChE and acceleration on CarE and GST. Overall results obviously depicted that semi-synthetic insecticide spinetoram and bioinsecticide matrine were recommended to control S. frugiperda with effective and long-lasting toxicity. Moreover, this study will provide basic information for sustainable control of S. frugiperda under field conditions in China.