Impact of emamectin benzoate on nucleopolyhedrosis virus infectivity of Spodoptera littoralis (Boisd.) (Lepidoptera: Noctuidae)

Abstract Background Attempts based on increasing the efficacy of Baculovirus and/or reducing the application concentration of synthetic insecticides through integrated lepidopteran management are appreciated role for conserving the environment. Impact of the multiple nucleopolyhedrosis virus (SpliMNPV) with emamectin benzoate (Em) against the cotton leaf worm, Spodoptera littoralis, was examined to identify the effective strategy for applying both agents in the control program successfully. Main body The LC50 and LC90 were drastically decreased from 1.9 × 106 and 1.0 × 1010 PIB/ml in SpliMNPV treatment to reach 8.87 × 101 and 1 × 104 PIB/ml, respectively in the SpliMNPV concentrations + Em LC25 treatment. This interaction was considered as potentiation. Larvicidal activity of Em was highly increased by Em concentrations + SpliMNPV LC25 treatment than the separately Em treatment; however, this interaction was considered as additive. Moreover, the mixture treatment (SpliMNPV LC99 + Em LC50) provided almost full protection of viral pathogenicity up to 48 h at natural exposure periods. Furthermore, the mixture treatment had a negative impact on the insect survival and reproduction of treated individuals. Conclusion Results indicated that the virus infectivity was increased by a mixture treatment of SpliMNPV + Em in particular facing UV sunlight, which causes virus degradation as well as reduced the effective doses of Em. These findings suggest that this simultaneous treatment maybe an effective technique to be applied in S. littoralis control strategy.