Rhynchophorus ferrugineus, also known as the red palm weevil, is regarded as the major pest of palm trees. Although studies of the microbiota associated with this species have been performed in recent years, little attention has been dedicated to the influence of the diet in shaping the host bacterial community. Here, we investigated the influence of food sources (i.e. palm tissues vs apple based substrate) on the microbial diversity associated with RPW, which was compared with the microbiota associated with wild individuals of the sister species Rhynchophorus vulneratus. The bacterial characterization was performed using a culture independent approach, i.e. the 16S rRNA pyrotag, and a culture dependent approach for a subset of the samples, in order to obtain bacterial isolates from RPW tissues. The bacterial community appeared significantly influenced by diet. Proteobacteria resulted to be the most abundant clade and was present in all the specimens of the three examined weevil groups. Within Proteobacteria, Enterobacteriaceae were identified in all the organs analysed, including hemolymph and reproductive organs. The apple-fed RPWs and the wild R. vulneratus showed a second dominant taxon within Firmicutes that was scarcely present in the microbiota associated with palm-fed RPWs. A comparative analysis on the bacteria associated with the palm tissues highlighted that 12 bacterial genera out of the 13 identified in the plant tissues were also present in weevils, thus indicating that palm tissues may present a source for bacterial acquisition.

h i g h l i g h t s Rhynchophorus species are polyphagous and some are pests of several palm species. We reviewed their natural enemies in both their native and introduced regions. More than 50 natural enemies have been reported to attack Rhynchophorus species. Fungi are the most promising ones for biological control.

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Invasive species usually act as carriers of their associated organisms like parasites and symbionts. This phenomenon has also occurred with the recent colonization of the red palm weevil, Rhynchophorus ferrugineus, in the Mediterranean area: this introduced pest is strictly associated with several species of mites (mainly belonging to the suborder Uropodina). In this paper, we document the high rate of infestation of Central and Southern Italian red palm weevil populations by the mite Centrouropoda almerodai. This mite species was found in all five investigated regions and infested the large majority of individuals (from 57 to 95%) by settling preferentially under the first pair of wings. Although this mite-weevil association is usually considered as a phoretic relationship, i.e. without impact on hosts, our study revealed that infested individuals have a significantly reduced lifespan (by one-third) in comparison with those not infested. Our study provides evidences that C. almerodai imposes a cost on its carrier host, at least under laboratory conditions, leading us to believe that the R. ferrugineus-C. almerodai relationship is also not phoretic in the wild.

Red Palm Weevil (RPW), Rhynchophorus ferrugineus represents one of the most dangerous pests of several species of palms. It spread from its native range (southeastern Asia) to the Middle East and then to the Mediterranean. Preliminary laboratory observations carried out on a group of males and females of RPW showed differential distribution of activity during daylight. Then we performed a field study comparing the time of captures of RPW across native populations (Vietnam) and invasive ones (Italy and Greece). Time of captures was also recorded for Rhynchophorus vulneratus from Malaysia (its native range). Weevils were trapped via traps baited with aggregation pheromone, kept continuously active for at least 20 days. Trapping times were recorded, and individuals were sexed after capture. Circular summaries indicate that arrivals at all the sampled localities were nonrandom, often with one or two peaks of arrivals during daylight. However, the distribution of trapping times was not consistent across populations and probably represents an answer to local environmental conditions.