Miscanthus spp. (Poaceae) is large perennial C4-grasses that are receiving considerable attention as bioenergy crops. Therefore, the introduction of miscanthus crops in Europe needs continuous monitoring and risk assessment because they may serve as a refuge or a reservoir for aphid pests and/or pathogens of conventional crops. Here, we first report the results of two field surveys conducted in northern France on the species composition of alate aphids flying above Miscanthus x giganteus crops. Then, in a first laboratory experiment, we investigated the colonization process on M. x giganteus of the four major aphid pests (Hemiptera: Aphididae) trapped in the field study. Results showed that the performances of these species in terms of feeding, survival, and reproduction, on M. x giganteus, depended on their degree of specialization toward Poaceae. The suitability of this plant was moderate for the Poaceae specialist aphid Rhopalosiphum padi (L.), low for the polyphagous aphid species, Aphis fabae (Scop.) and Myzus persicae (Sulzer) and very low for the Brassicaceae specialist aphid Brevicoryne brassicae (L.). Nevertheless, M. x giganteus cannot be considered as a reservoir crop for these common aphid pests as their progenies did not reach the adult stage. In a second laboratory experiment, the ability of the Poaceae specialist aphid R. padi to colonize M. x giganteus and its putative parents, Miscanthus sinensis and Miscanthus sacchariflorus was assessed. Results showed that R. padi was able to achieve its life cycle on M. sacchariflorus but not on M. sinensis. The consequences of the introduction of miscanthus in the north of France are discussed in terms of phytoviruses spreading and in terms of potential reservoir for aphid pests from conventional neighboring crops.