[in Dutch with English abstract: ] In the first half of the previous century poplars were planted on the borders of the Meuse to mark the fairway for inland vessels during high water levels. On fallen branches of one of those poplars Athallia pyracea was found, a species considered rare in the Netherlands and only known from a few locations in the ultimate south. After it was found on many trees in the surroundings a more structured approach was chosen to investigate the occurrence of A. pyracea and accompanying species. 51 branches were collected from various locations along the river on a stretch of around 50 km. Those branches were inspected microscopically and in association with Athallia pyracea the species Athallia cerinella, Athallia cerinelloides, Lecanora sambuci and Lecanora hagenii were found. It seems that the association Lecanoretum sambuci recently settled on poplar in the Netherlands, as predicted by van Dort et al. (2017). We encourage everyone to give a close look for these species on poplar branches in their surroundings.