Red palm weevil, Rhynchophorus ferrugineus (Oliver, 1790), Order; Coleoptera, Family; Curculionidae, is considered as the biggest threat facing date palm cultivators. The larva feed on trunk tender tissue and can cause palm death within 6-8 months after infection. Insect gut harbors a community of bacteria that lives in an endosymbiotic relationship with the insect and it is strongly evident that it plays a key role in insect life. Deciphering and identification of insect microbiota could lead to the development of new symbiotiont-based control approaches. In this work we studied the diversity of the endosymbiont bacterial community of red palm weevil larval midgut in Egypt, by using Denaturing Gradient Gel Electrophoresis (DGGE), based on 16S rRNA genes PCR amplification. We used three groups of field caught larva sampled from two different places; El-Badrashin and Agricultural Research Center (ARC) in Giza governorate, Egypt. DGGE profiling patterns has shown the relative prevalence of bacterial phylotypes  affiliated to family Firmicute; Leuconostoc lactis, Lactococcus lactis, Lactobacillus nagelli and bacterial phylotypes affiliated to family Actinobaceria; Cellulomonas cellasea, Bifidobacterium minimum, which suggest that they have a potential role in nutrition, physiology and immunomodulation of the insect.

The efficacy of the entomopathogenic fungus Beaveria bassiana Saudi Arabian isolate (B-SA3)was evaluated against the red palm weevil, Rynochophorus ferrungineus (Oliv.).The mentioned isolate was assessed on the different developmental stages of the red palm weevil through toxicity tests, i.e. determination of lethal concentration and lethal times to kill 50% of treated insects. The results showed that 8th instar larvae were the most tolerant followed by pupa to B.bassiana as their LC50 values were 3.75x 108 and 3.78x 107 conidia/ ml, respectively. Meanwhile, 4th instar larvae were the most susceptible to infection by B.bassiana (B-SA 3), as LC50 value was 3.25x 106 conidia/ ml, which proved insignificantly different to that determined in adult weevils, i.e. 4.18x 106 conidia /ml. Furthermore, LT50 values were very similar in these latter mentioned developmental stages in any considered concentration; meanwhile, LT50 was much longer in 8th instar larvae than the other considered instar and/or developmental stages. The fungus B. bassiana was most virulent to eggs of the red palm weevil as none of the eggs hatched following their treatment with any of the considered concentrations (ranging between 5x 109 to 5x105 conidia /ml). Moreover, germination viability of harvested conidia of B.bassiana stored at -4°C was insignificantly affected up to the 10th month storage period and was well above 90%. However, germination percentage of conidia then decreased to 70.27% after 16 months of storage. Also, the virulence of the stored conidia was tested after 1, 6, 12 and 16 months on adult red palm weevils, the LC50 values were 3.75x106, 4.66x106, 4.17x107 and 3.37x108 conidia/ ml, respectively. These results show that there was a significant decrease in the virulence of the tested fungus when the duration of storage period was more than 10 months.