Management of Deleterious Effect of Fusarium oxysporum Associated with Red Palm Weevil Infestation of Date Palm Trees

Red palm weevil (RPW) is a dangerous pest that infects the date palm tree and makes tunnels in the tree’s trunk. RPW infection is followed by secondary invaders of microorganisms that cause degradation of the trunk tissues leading to toppling the crown and death of the tree in a short time. This study showed that Fusarium oxysporum Schlecht. was the common fungal species isolated from the root and trunk tissues of the date trees infested with RPW, which recorded 100% of frequency. Pathogenicity of 4 isolates of F. oxysporum was confirmed on date palm seeds and seedlings. The results confirmed that all isolates involved in rot of the germinated seeds (40–100% incidence), root rot, and death of palm seedlings (20–100%) under artificial infection as well as degradation of date palm petioles. Application of 20 L/palm of systemic fungicide (Topsin) at 1% as foliar and soil drench of date palm for successive three times successfully reduced development of the deterioration and suppressed the growth of F. oxysporum. Interestingly this fungicide did not suppress the growth of Trichoderma viride Pers. So, our results recommend this fungicide to suppress the pathological and degradable activities of F. oxysporum during the integrated pest management of RPW on date palm trees.

CURRENT STATUS, CHALLENGES, MANAGEMENT AND FUTURE PERSPECTIVES OF THE RED PALM WEEVIL Rhynchophorus ferrugineus OLIVIER (COLEOPTERA, CURCULIONIDAE) ERADICATION - A REVIEW

The date palm is a cultural and economic heritage of many nations. The red palm weevil, Rhynchophorus ferrugineus Olivier (Coleoptera, Curculionidae) is among the world’s most serious insect pests of palms that have rapidly expanded its geographical distribution and host plant range during the last decades. Integrated pest management (IPM) is followed to suppress the pest using the most economical and least hazardous methods to humans and the environment. Since R. ferrugineus is a serious pest of date palm production worldwide, farmers, researchers, and scientists have developed many tactics to eradicate this pest. However, there was no published article covering and integrating the current status, biology, ecology, and future control tactics of R. ferrugineus and proposes an IPM program. Therefore, in this review, R. ferrugineus geographical distribution, host plant range, economic importance, infestation symptoms, morphology, biology, and its management tactics were thoroughly discussed. These tactics include early detection of R. ferrugineus infestation, trapping, chemical applications, use of bio-agents, bioinsecticides (plant extracts), resistance cultivars, cultural practices, sterile insect technique, gene silencing technology, quarantine, and geographical information system. In conclusion, all available control tactics suggest that R. ferrugineus could be successfully managed by developing IPM programs comprising several means of control. It is hoped that this review will highlight some aspects of date palm management and raise research gaps and directions deserving further investigations to develop a better understanding of R. ferrugineus management and therefore contributes to the sustainability of date palm cultivation worldwide.

Proteomics and Interspecies Interaction Analysis Revealed Abscisic Acid Signalling to Be the Primary Driver for Oil Palm’s Response against Red Palm Weevil Infestation

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.

Silencing of vitellogenin gene contributes to the promise of controlling red palm weevil, Rhynchophorus ferrugineus (Olivier)

Red palm weevil [Rhynchophorus ferrugineus (Olivier)], is native to South Asia and expanding its distribution range globally. Recent invasions of red palm weevil around the world, including Saudi Arabia, has become a global constraint for the production of palm species. Although, several control measures have been tested, none of them seemed successful against this invasive species. Therefore, we focused on silencing the reproduction control gene vitellogenin (Vg) based on RNA interference (RNAi) strategy for its possible application in the management of R. ferrugineus. The Vg is a major yolk protein precursor critical for oogenesis. To do this, fat body transcriptome of R. ferrugineus female adults was sequenced, which provided partial Vg gene transcript (FPKM 5731.60). A complete RfVg gene transcript of 5504 bp encoding 1787 amino acids was then sequenced using RCAE-PCR strategy and characterized. Phylogenetic analysis suggested that RfVg has closer ancestry to the coleopteran insects. The RfVg-based RNAi significantly suppressed the expressions of Vg gene. The 15, 20 and 25 days post-injection periods suppressed Vg expressions by 95, 96.6 and 99%, respectively. The suppressed Vg expressions resulted in the dramatic failure of Vg protein expression, which caused atrophied ovaries or no oogenesis and ultimately eggs were not hatched. These results suggest that knockdown of Vg gene involved in R. ferrugineus reproduction is a promising target for RNAi-based management of R. ferrugineus.

Biocontrol potential of entomopathogenic fungi, nematodes and bacteria against Rhynchophorus ferrugineus (Olivier)

Background The red palm weevil (RPW), Rhynchophorus ferrugineus (Olivier) (Coleoptera: Curculionidae), is a serious threat to date palms across the globe, causing heavy yield losses. The pest inflicts damage to palms stem and destroys vascular system; resultantly lower the vigor and affect the growth and yield. For ecological farming system, biological control of the pest is gaining increased interest due to hosts’ specificity, safety to human, animal and non-target organisms, and their compatibility to environment. Results In laboratory assay, Beauveria bassiana, Heterorhabditis bacteriophora and Bacillus thuringiensis var. kurstaki (Bt-k) alone and in combination against sixth instar larvae and adults of four distinct populations of RPW were applied. H. bacteriophora was more effective, followed by B. bassiana and Bt-k in alone treatments. While in combined treatments, the highest mortality was recorded for H. bacteriophora + B. bassiana combination (100% for both stages), followed by H. bacteriophora + Bt-k, (larvae 100%; adults 94.24%) and B. bassiana + Bt-k treatments (larvae: 87.01%; adults: 80.53%). Maximum rate of mycosis (larvae 85.74%; adults 69.07%), sporulation (larvae 189.22 conidia ml−1; adults 164.56 conidia ml−1), cadavers affected by nematodes (larvae 92.4%; adults 81.29%) and nematode production (larvae 178.78 IJs ml−1; adults 153.44 IJs ml−1) was observed where B. bassiana or H. bacteriophora was applied alone and the lowest (larvae 122.78 IJs ml−1; adults: 103.22 IJs ml−1) was recorded for H. bacteriophora + B. bassiana combination. Conclusions Entomopathogens can be effectively used alone and/or in integration to control RPW populations. Natural capability of entomopathogens to infect and disseminate into other hosts makes them excellent biocontrol agents to be incorporated in the IPM plan of RPW and to make palm growers confident with the use of the most promising microbial control agents.

Perspectives for Synergic Blends of Attractive Sources in South American Palm Weevil Mass Trapping: Waiting for the Red Palm Weevil Brazil Invasion

Coupling several natural and synthetic lures with aggregation pheromones from the palm weevils Rhynchophorus palmarum and R. ferrugineus reveals a synergy that results in an increase in pest captures. The combined attraction of pure pheromones, ethyl acetate, and decaying sweet and starchy plant tissue increases the net total of mass-trapped weevils. The 2018 entrance of the red palm weevil (RPW) into South America has threatened palm-product income in Brazil and other neighboring countries. The presence of the new A1 quarantine pest necessitates the review of all available options for a sustainable mass-trapping, monitoring, and control strategy to ultimately target both weevils with the same device. The effective lure-blend set for the mass-trapping system will attract weevils in baiting and contaminating stations for entomopathogenic fungi that the same weevils will spread.

A Comparative Study on the Microbial Communities of Rhynchophorus ferrugineus (Red Palm Weevil)-Infected and Healthy Palm Trees

Several studies have investigated palm trees’ microbiota infected with red palm weevil (RPW) (Rhynchophorus ferrugineus), the major pest of palm trees. This study compared the microbial communities of infected and uninfected palm trees in the Hail region, Northern Saudi Arabia, determined by high-throughput 16S rRNA gene sequencing by Illumina MiSeq. The results indicated that taxonomic diversity variation was higher for infected tree trunk than the healthy tree trunk. Soil samples from the vicinity of healthy and infected trees did not have a significant variation in bacterial diversity. Myxococcota, Acidobacteriota, and Firmicutes were the dominant phyla in RPW-infected tree trunk, and Pseudomonadaceae was the most prominent family. This study is the first report on the characterization of RPW-infected and healthy palm trees’ microbiome.