The red palm weevil (RPW) is a stem boring Coleoptera that decimates host palm trees from within. The challenge of managing this pest is due to a lack of physical symptoms during the early stages of infestation. Investigating the physiological changes that occur within RPW-infested palm trees may be useful in establishing a new approach in RPW detection. In this study, the effects of RPW infestation were investigated in Elaeis guineensis by observing changes in physical and physiological parameters during the progress of infestation by visual inspection and the comparison of growth, gas exchange, stomatal conductance, and chlorophyll content between the non-infested control, physically wounded, and RPW-infested E. guineensis groups. During the study period, four distinct levels of physical infestation were observed and recorded. The RPW-infested group displayed significantly lower maximum photosynthesis activity (A_max) starting from the third week post-infestation. However, growth in terms of change in plant height and stem circumference, leaves’ stomatal conductance, and chlorophyll content were not significantly different between the three groups during the duration of the study. The significant drop in photosynthesis was observed one week before physical changes appeared. This suggests the promising utilisation of photosynthesis activity as a signal for detecting RPW infestation at the early stage of attacks, which could be useful for integration in integrated pest management (IPM).

The red palm weevil (RPW; Rhynchophorus ferrugineus Olivier (Coleoptera Curculionidae)) is an invasive insect pest that is difficult to manage due to its nature of infesting the host palm trees from within. A holistic, molecular-based approach to identify proteins that correlate with RPW infestation could give useful insights into the vital processes that are prevalent to the host’s infestation response and identify the potential biomarkers for an early detection technique. Here, a shotgun proteomic analysis was performed on oil palm (Elaeis guineensis; OP) under untreated (control), wounding by drilling (wounded), and artificial larval infestation (infested) conditions at three different time points to characterise the RPW infestation response at three different stages. KEGG pathway enrichment analysis revealed many overlapping pathways between the control, wounded, and infested groups. Further analysis via literature searches narrowed down biologically relevant proteins into categories, which were photosynthesis, growth, and stress response. Overall, the patterns of protein expression suggested abscisic acid (ABA) hormone signalling to be the primary driver of insect herbivory response. Interspecies molecular docking analysis between RPW ligands and OP receptor proteins provided putative interactions that result in ABA signalling activation. Seven proteins were selected as candidate biomarkers for early infestation detection based on their relevance and association with ABA signalling. The MS data are available via ProteomeXchange with identifier PXD028986. This study provided a deeper insight into the mechanism of stress response in OP in order to develop a novel detection method or improve crop management.

The red palm weevil, Rhynchophorus ferrugineus, is a destructive, invasive pest to a diverse range of palm plantations globally. Commonly used broad-range chemical insecticides for insect control pose high risks to non-target organisms, humans, and the environment. A bio-rational approach of screening natural small-molecule inhibitors that specifically target R. ferrugineus proteins critical to its life processes can pave the way for developing novel bioinsecticides. Digestive enzymes (DEs), which impair feeding on plants (herbivory), are promising targets. We generated de novo transcriptomes, annotated DE-related genes from the R. ferrugineus gut and abdomen, manually annotated the DE gene family from the recently available genome and our transcriptome data, and reported 34 glycosidases, 85 lipases, and 201 proteases. We identified several tandem duplicates and allelic variants from the lipase and protease families, notably, 10 RferLip and 21 RferPro alleles, which emerged primarily through indels and single-site substitution. These alleles may confer enhanced digestive lipolysis and proteolysis. Phylogenetic analyses identified and classified different subfamilies of DEs and revealed close evolutionary relationships with other coleopterans. We assessed select candidate DEs’ activity and the potential for inhibition in silico to better understand the herbivory arsenal. In silico analysis revealed that the selected enzymes exhibited similar ligand-binding affinity to their corresponding substrate, except for protease aminopeptidase N, RferPro40, which exhibited poorer affinity to the inhibitor bestatin. Overall, our study serves as a foundation for further functional analysis and offers a novel target for the development of a novel bio-rational insecticide for R. ferrugineus.