Effectiveness of botanical insecticides on larval stage of red palm weevil Rhynchophorous ferrugineus and survival of entomopathogenic nematodes

AbstractBotanical oils are considered ecofriendly compounds with insecticidal characteristics. In this study, the effects of basil (Ocimum basilicum), camphor (Cinnamomum camphora), cinnamon (Cinnamomum verum), lemon (Citrus limon), clove (Syzygium aromaticum), ginger (Zingiber officinale), black pepper (Piper nigrum), and orange (Citrus sinensis var balady) oil extracts on the survival of four entomopathogenic nematode strains belonging to the Steinernema and Heterorhabditis genera, as well as their impacts on Rhynchophorus ferrugineus egg hatching and larvae, were assessed. The results for the camphor, lemon, black pepper, and orange oils were promising as 50 μL/mL of each resulted in 0%, 0%, 16%, and 0% hatchability for the R. ferrugineus eggs, respectively. Furthermore, the mortality of R. ferrugineus larvae was up to 95% with the similar concentrations and an exposure time of 48 h, for the other investigated oils. Various morphohistopathological alterations were found in the cuticle; outer cuticle folds swelling or shrinkage and subcuticular muscle degeneration, as well as midgut; fat globules in the epithelial lining with marked degeneration and/or necrosis, of the R. ferrugineus larvae when compared with those of controls replicates. Mortality percentage of infective juveniles (IJs) of Steinernema carpocapsae (S2) was significantly lower than Heterorhabditis marelatus (D1), Steinernema riobravae (Sr) and Steinernema carpocapsae (All) when using camphor oil compared to the other oils (50%). From the obtained observations on oils lethal effects, the target of developing integral biocontrol product formulated from combinations of essential oils and nematode with insecticidal properties against R. ferrugineus (not nematode survival) is possible; a sustainable and ecofriendly product for pest management.Keywords: Red palm weevilSteinernema spp.Heterorhabditis spp.essential oilintegrated pest management AcknowledgmentThe authors would like to thank the field investigators, who helped in collecting specimens in investigated locality. The authors gratefully thank the Genetic Engineering and Biotechnology Research Institute-University of Sadat City, and National Research Centre- Dokki for their support of this paper with the infrastructure and facilities to carry out the research plan.Disclosure statementThe authors report there are no competing interests to declare.Data availability statementData are available from the corresponding author upon request.Additional informationFundingThis study was a part of the following research projects in the National Research Centre, Egypt: nt.allam@nrc.sci.eg Molecular Approaches for Characterization, Phylogenetic Analysis, and Diagnosis of Oestrus ovis, Cephalopina titillator, and Rhinoestrus spp. Larvae Obligatory Parasitizing Sheep, Goats, Camels, and Equines [No. 10120507] and Nanoparticle Construction of recombinant Txp40-Cyclopeptides candidates attached to Phenols and Flavonoids fractions as novel preparation applied in biological control of some nasal myiasis inducing parasites [No. 11040301].