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Dutch elm disease (DED) is a destructive tracheomycosis caused by Ophiostoma novo-ulmi, an ascomycete that is devastating natural elm populations throughout Europe, North America and part of Asia. The fungus is mainly spread by elm bark beetles (Coleoptera: Curculionidae, Scolytinae) that complete their life cycle between healthy and diseased elms. It has recently been shown that certain fungi of the genus Geosmithia, associated with bark beetles, are involved in the DED patho-system. It has been observed that the two fungi not only share the same habitat in the host plant and during each developmental stage of the insect, but that there is a close association between them. By analyzing the presence and quantity of the two fungi on the bodies of elm beetles by a duplex qPCR assay, this work aimed to explore the dynamic of the relationship among the adults of S. multistriatus, O. novo-ulmi and Geosmithia spp. at sites characterized by different DED severity levels during the elm growing season. We observed that, regardless of the epidemiological conditions, both fungi are always present on adult flickering insects. The proportion of the two fungal populations varies between sampling sites, with Geosmithia spp. being predominant. This study confirms a strong relationship between the microorganisms, but it cannot give support to the hypothesis suggested in previous works regarding a putative hyperparasitic activity of Geosmithia spp., towards O. novo-ulmi. The hyperparasitism of Geosmithia towards O. novo-ulmi within this tri-trophic system should be investigated further for potential use as biological control agent.