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

Public demand for the reduction, or even total elimination, of chemical residues in agricultural products, coupled with increased concerns about the detrimental environmental effects of chemical or synthetic pesticides, facilitated the need to develop alternative pest control means in agriculture. Microbial control agents (MCAs) are considered an attractive alternative to chemical insecticides due to ecological safety with no residues, wide host range, and competitive prices. Here, we evaluated several insect-killing fungi as a preventative control measure against the destructive palm pest, the red palm weevil (RPW), in lab experiments and in the greenhouse. The fungi were applied on healthy Washingtonia palms as a protective mean prior to being challenged with the RPW. The results demonstrated that treated palms were significantly less colonized by the RPW, and the fungi prevented the establishment of this severe pest. This study is the first stage in our bigger research endeavor for protecting date palm plantations with EPF.The red palm weevil (RPW) Rhynchophorus ferrugineus is a highly destructive invasive pest for palms whose management is mainly by application of synthetic pesticides. As a key pest of date palm plantations, it is necessary to integrate environmentally safe measures for its management. 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 (R), 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 suspension or dry formulation significantly inhibits infestation signs and results in protection. These results lay the foundation for investigating the protective rate of EPF products against RPW in date plantations.