An Australian Endemic Fungus, Metarhizium rileyi as an effective biopesticide for managing Fall Armyworm (Spodoptera frugiperda)

Abstract

Fall Armyworm FAW (Spodoptera frugiperda) invaded Australia in 2020 and spread rapidly throughout the country. It has been a particular issue for sweetcorn, maize, sorghum and other grains and pasture crops. It has caused considerable damage to crops because of its rapid development time, and its ability to cause significant damage in short time periods, sometimes resulting in complete crop losses before the plants are established. Furthermore, when FAW entered Australia, it was already resistant to multiple chemical pesticides. Some growers are currently having to spray a limited number of effective chemicals numerous times to manage FAW; which is unsustainable for managing pesticide resistance, developing IPM strategies and preserving beneficial arthropods.
In response, our research has explored the efficacy of endemic insect pathogens as biopesticides. Laboratory bioassays and field trials were conducted to assess the effectiveness of exotic and endemic nuclear polyhedrosis viruses (NPVs) and the fungus Metarhizium rileyi against FAW. Our research has shown that the NPVs are not effective at managing FAW. However, in sweetcorn field trials we demonstrated significant reductions in FAW populations with the application of an endemic M. rileyi, positioning it as a promising biopesticide for FAW management. Our trials have demonstrated that an M. rileyi biopesticide can be as effective as a leading modern chemical insecticide. Furthermore, it is very unlikely to disrupt beneficial arthropods, develop resistance or have residue problems. An M. rileyi biopesticide could provide an IPM compatible alternative product which could greatly reduce farmers reliance on chemical pesticides.