Lethal and transgenerational effect of chlorpyrifos, Imunit and <i>Metarhizium anisopliae</i> on the survival, immunity and demographic parameters of <i>Rhynchophorus ferrugineus</i> Olivier

Abstract Background: Red palm weevil, Rhynchophorus ferrugineus Olivier is a serious pest of date palm groves in Pakistan, which is the sixth-largest date palm producer around the globe. Currently, this pest is managed with synthetic insecticides, which negatively impact human health, the environment and resistance issues. To mitigate these problems, biocontrol agents such as entomopathogenic fungi, which are ecologically safe and environmentally friendly alternatives, need to be integrated. Methods: In the current study, the lethal effect of Metarhizium anisopliae, Imunit (alpha-cypermethrin + teflubenzuron) and chlorpyrifos were determined on the demographic parameters of the R. ferrugineus using age stage two sex life table software. Lethal concentration (LC 50 ) of chlorpyrifos, Imunit and Metarhizium anisopliae i.e. 8.060mg/L, 1.114 mg/L and 2.9×10 4 conidia/mL, respectively were determined on 2nd instar grub. Results: The current study showed that Imunit-treated group experienced a decrease in grubs, adult male and female duration, and significantly a decreased fecundity rate compared to the chlorpyrifos, M. anisopliae and control - treated groups. Also, adult pre-oviposition period (APOP), total pre-oviposition period (TPOP) and oviposition days (O d ) were decreased in the Imunit-treated group compared to the other pesticides-tested group. Imunit-treated group showed reduced mean generation time ( T ) and net reproduction rate ( R 0 ) compared to all tested pesticides. Moreover, the effect of M. anisopliae, Imunit and chlorpyrifos on the detoxification enzymes such as glutathione S-transferases (GST), esterases (EST) and acetylcholinesterase (AChE) on 3rd, 5th and 7th day showed highest activity of these enzymes on the 3rd day of treatment in chlorpyrifos-treated group and in Imunit-treated group. The lowest activity of these enzymes was observed in M. anisopliae and control-treated group, which showed the chances of resistance against M. anisopliae is less than chlorpyrifos- and Imunit-treated group. Conclsuion: The Imunit insecticide and M. anisopliae have adverse and long lasting effects on the R. ferrugineus population. In the future, M. anisopliae should be incorporated with Imunit pesticides to manage R. ferrugineus eco-friendly.