Combination of a Nano-Emulsion Formulation of Metarhizium anisopliae with a Catch and Release Pheromone Trap for the Management of Red Palm Weevil in Coconut

The red palm weevil (RPW, Rhynchophorus ferrugineus Olivier) (Coleoptera: Curculionidae) is a damaging insect pest of coconut in Malaysia. Severe infestation can kill the infested coconut trees. RPW is currently managed by chemical measures, removal of infested coconut trees and mass trapping of adult weevils by using pheromone traps. In 2020-2021, Malaysian Agricultural Research and Development Institute (MARDI) and Universiti Malaysia Terengganu (UMT) conducted collaborative research to develop a biological control system for RPW by using a nano-emulsion formulation of an entomopathogenic fungus, Metarhizium anisopliae (MET-GRA4), combined with a new design of catch-and-release pheromone trap. The mechanism began with a pheromone that attracts RPW to enter the trap. Upon entering through the inlet funnel, the beetle passes through gauze saturated with the emulsion, wetting its body with the MET-GRA4 emulsion, which is sprayed at the inlet funnel, particularly the gauze area, according to the pre-set intervals. Since the RPW cannot access the pheromone and food bait inside the trap due to the inlet hole is covered by a gauze, it will eventually exit and return to its population. The spores of MET-GRA4 start infecting the weevil's body 48-72 hours after exposure, leading to its death. This biological control method aims to infect the entire RPW population within the area. Three RPW hotspot locations were selected as evaluation sites in Kelantan (Kota Bharu, Pasir Putih and Bachok) and Terengganu (Kuala Terengganu, Kuala Nerus and Marang), respectively. Comparison of RPW population at the sites before and after treatment with the biological control system applications showed 28.78% reduction in Kelantan and 60.27% in Terengganu. Impacts of the RPW population reduction were significant in both states. This environmentally friendly innovation has the potential to be used for monitoring, surveillance and control of RPW in coconut planting areas as well as in other palms.