Efficacy of Entomopathogenic Fungi as Prevention against Early Life Stages of the Red Palm Weevil, Rhynchophorus ferrugineus (Coleoptera: Curculionidae) in Laboratory and Greenhouse Trials

The red palm weevil (RPW) Rhynchophorus ferrugineus is highly destructive invasive pest for palms whose management is mainly by application of synthetic pesticides. Entomopathogenic fungi (EPF) have been primarily studied as a preventative control measure due to the horizontal transfer of conidia within the RPW population. We previously demonstrated the horizontal transmission of fungal conidia from an egg-laying surface to the female weevil and then to the eggs and larvae. Based on that strategy, this study aimed to evaluate the virulence of commercial EPF products and laboratory EPF preparations to RPW females and their progeny and their ability to protect palms against infestation. As such, it serves as a screening platform for field experiments. Mortality rates of females and eggs depended on the applied treatment formulation and fungal strain. Velifer®, a Beauveria bassiana product, and Metarhizium brunneum (Mb7) resulted in 60–88% female mortality. Mb7—as a conidial suspension or powder—resulted in 18–21% egg-hatching rates, approximately 3 times less than in the non-treated control. Treating palms with Mb7 significantly inhibits infestation signs and results in 75% and 100% protection, respectively. These results lay the foundation for investigating the protective rate of EPF products against RPW in date plantations.