Since 2008, ash trees are threatened in Switzerland by ash dieback (ADB), a fungal disease introduced from Asia to Europe. While more than 90% of the trees suffer from the disease, some few are almost symptom-free. A survey revealed 397 seemingly tolerant trees on 144 sites in Switzerland, north of the Alps. However, a new pest has the potential to kill the remaining ash trees: the emerald ash borer (EAB), an asian wood boring beetle. Started early 2019, the project has for aim to test the seemingly tolerant ash trees discovered in Swiss forests against emerald ash borer and new asiatic strains of the ash dieback pathogen. Therefore, 10 adapted ash tree sites were chosen over Switzerland. From each site, one tolerant and one diseased ash tree were selected and replicated 50 times using grafting. All tests will be conducted under secured conditions in the new Plant Protection Lab @ WSL.