BackgroundThe date palm root borer Oryctes agamemnon (Coleoptera: Scarabaeidae) is one of the major pests of palms. In Saudi Arabia, both larvae and adults of Oryctes are particularly troublesome, especially during the establishment of young date palm orchards. Endosymbiotic bacteria are known to have a key role in food digestion and insecticide resistance mechanisms, and therefore are essential to their host insect. Identification of these bacteria in their insect host can lead to development of new insect pest control strategies.ResultsMetagenomic DNA from larval midgut of the date palm root borer, O. agamemnon, was analyzed for endosymbiotic bacterial communities using denatured gradient gel electrophoresis (DGGE) utilizing 16S rRNA genes. The DGGE fingerprints with metagenomic DNA showed predominance of eleven major operational taxonomic units (OTUs) identified as members of Photobacterium, Vibrio, Allomonas, Shewanella, Cellulomonas, and Citrobacter, as well as uncultured bacteria, including some uncultured Vibrio members. DGGE profiles also showed shifts in the dominant bacterial populations of the original soil compared with those that existed in the larval midguts. The endosymbiotic bacterial community was dominated by members of the family Vibrionaceae (54.5%), followed by uncultured bacteria (18.2%), Enterobacteriaceae (9.1%), Shewanellaceae (9.1%), and Cellulomonadaceae (9.1%). Phylogenetic studies confirmed the affiliation of the dominant OTUs into specified families revealed by clustering of each phylotype to its corresponding clade. Relative frequency of each phylotype in larval midguts revealed predominance of Vibrio furnisii and Vibrio navarrensis, followed by uncultured bacterial spp., then Cellulomonas hominis, Shewanella algae, and Citrobacter freundii.ConclusionAnalysis of metagenomic DNA for endosymbiotic bacterial communities from the midgut of Oryctes larvae showed strong selection of specific bacterial populations that may have a key role in digestion, as well as other benefits to the larvae of O. agamemnon. Determination of the distinct endosymbiotic community structure and its possible biological functions within the insect could provide us with basic information for future pest control research.

Culex pipiens is the most abundant mosquito in Al-Madinah Al-Munawwarah region, Saudi Arabia, transmitting several diseases like elephantiasis, avian malaria, and arboviruses. It has become resistant to several insecticides worldwide, and the search for new alternatives should be prioritized. Because of their biological profile and eco-friendly nature, ionic liquids (ILs) have recently attracted the attention of biologists. The present study was carried out to evaluate the effect of six ILs against C. pipiens larvae. Larval mortality, LC 50 , LC 90 , LT 50 and residual activity of ILS were determined. Aqueous solutions of tested ILs showed up to 100% larval mortality 24 h after exposure. Significant concentration-and time-based differences in larval mortality were found for a given IL as well as between different ILs. Ultimately, the ILs tested in the current study could be arranged in descending order according to their toxicity against larvae as follows: IL7, IL5, IL4, IL1, IL2 and IL6.

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