Effects of Empedobacter brevis on insecticidal activity and detoxification enzymes of Spodoptera frugiperda

【Objective】To investigate effects of Empedobacter brevis on insecticidal activity and detoxification enzymes of Spodoptera frugiperda, so as to provide theoretical basis for its efficient green control.【Method】 Indoor insecticidal activity of E. brevis to S. frugiperda 1^st, 2^nd and 3^rd instar larvae were tested with leaf immersion method. Field control effects of E. brevis to S. frugiperda were carried out using the spray method. The detoxification enzymesglutathione S-transferase(GST) and carboxylesterase(CarE)and acetylcholinesterase(AChE) of S. frugiperda larvae treated with sublethal concentration of E. brevis were detected by the microplate reader.【Result】Indoor insecticidal activity results showed that E. brevis was strongly toxical to S. frugiperda larvae. The adjusted mortality rate of 1^st, 2^nd and 3^rd instar larvae fed on maize leaves treated with 1.00×10⁷ spores/mL E. brevis for 72 h were 86.21%, 83.05% and 58.33%, respectively. In the corn field after spraying 1.0×10¹⁰ spores/mL of E. brevis suspension concentrate(SC) at 800 and 1000 times for 7 d, the control effects were 95.84% and 93.78%, significantly higher than that of 0.5% matrine aqueous solutions(SL) (P<0.05) but it had no significant difference with 200 g/L chloranbenzoamide SC(P>0.05). GST, CarE and AChE activity of S. frugiperda larvae were decreased after the sublethal concentration(LC₂₀) of E. brevis treatments.【Conclusion】 E. brevis has strong insecticidal activity and field control effect against larvae of S. frugiperda, and it can be used as an effective biological pesticide for controlling S. frugiperda. It is suggested that 1.0×10¹⁰ spores/mL of E. brevis SC at 800 and 1000 times can be sprayed at occurrence period of early-instar S. frugiperda larvae on cornfield to control the damage.