Interactions between microorganisms associated with red palm weevil, Rhynchophorus ferrugineus, in Tunisia

The aims of this study were to determine the microorganisms associated with Rhynchophorus ferrugineus and to define the different interactions created between them. Macroscopic examination of R. ferrugineus specimens revealed the presence of a mite, which was identified as Centrouropoda almerodai. Mites were found in the thorax, the antennae, the rostrum, and the legs of adults. They were massively detected in elytra. However, red palm weevil larvae carried a low number of mites. Also, 57% of R. ferrugineus larvae and 62% of R. ferrugineus nymphs were infected with an entomopathogenic fungus, Beauveria bassiana. This fungal infestation was not observed on red palm weevil adults. Based on molecular identification, the nematodes associated with red palm weevil are very similar to Teratorhabditis synpapillata (99.9% similarity). The number of nematodes ranged between 95 and 538 per insect on average. Teratorahabditis synpapillata had no parasitic effect on R. ferrugineus adults compared to the control. Nematode-insect interaction bioassays revealed that T. synpapillata is capable of infesting R. ferrugineus larvae. Galleria mellonella larvae treated with T. synpapillata (am8) revealed a high mortality of 90%. The interactions between R. ferrugineus's fauna were tested in vitro using Petri plates containing agar medium. The different bioassays of the interactions established between R. ferrugineus's fauna showed that no relationship (trophism or commensalism) was created between them compared to the control. Our results point out that it's necessary to determine the fauna of R. ferrugineus and to show how they interact, especially given that B. bassiana and the nematode T. synpapillata have a parasitic potential against red palm weevil.