Feeding dsSerpin1 Enhanced Metarhizium anisopliae Insecticidal Efficiency against Locusta migratoria manilensis

RNA interference (RNAi) induces gene silencing in order to participate in immune-related pathways. Previous studies have shown that the LmSerpin1 gene upregulates the immune responses of Locusta migratoria manilensis , and that the infection of locusts with Metarhizium anisopliae can be enhanced through the injection of the interfering dsSerpin1 . In this study, dsRNA was synthesized from the Serpin1 gene and fed to the third instars of L. m. manilensis at concentrations of 5 μg, 10 μg, and 20 μg. Feeding dsSerpin1 increased the mortality of L. m. manilensis , and 20 μg dsSerpin1 had the highest lethality, followed by 10 μg dsSerpin1, with the lowest being observed at 5 μg dsSerpin1 . Serpin1 silencing and temperature fever induction by feeding with dsSerpin1 had a strong synergistic effect on M. anisopliae , showing a dose-dependent response. When L. m. manilensis were fed on a diet containing 20 μg dsRNA and M. anisopliae (2.5 × 10 8 spores/g wheat bran), 3-day mortalities significantly increased. The dsSerpin1 plus M. anisopliae treatments resulted in a 6-day mortality of 60%, accelerating insect death. These results indicated that feeding with dsSerpin1 could be an effective way to control pests and that the control effect and dsRNA concentration were dose-dependent within the first seven days. In particular, 20 μg was an effective dosage to enhance the insecticidal efficiency of M. anisopliae .