Kirisits, T. 2017. Further Observations on the Association of Hymenoscyphus fraxineus with Fraxinus ornus. Baltic Forestry 23(1): 60-67.

  Results of ash dieback symptom observations on 15 seedlings each of Fraxinus ornus (flowering ash) and Fraxinus excelsior (common ash) which were planted on a forest site in south-eastern Austria where they were exposed to natural inoculum (ascospores) of the ash dieback pathogen Hymenoscyphus fraxineus in the growing seasons of 2014 and 2015 are presented. During the observations, until early March 2016 (572-845 days after the seedlings had been planted), necrotic lesions in the bark and wood discoloration, alone or in combination with leaf wilting and/or dieback due to girdling, were cumulatively recorded on all 15 and leaf symptoms associated with H. fraxineus on 14 out of the 15 F. excelsior seedlings. In contrast, no ash dieback symp-toms on woody parts occurred on any of the F. ornus seedlings. In autumn 2014 and 2015, a few flowering ash leaves with inconspicuous necrotic lesions on the leaf rachis were observed, and H. fraxineus was isolated from 9 out of 20 (45%) symptomatic rachises, and once also from a necrotic leaflet midrib. The observations and fungal isolations confirm and strengthen previous appraisals that F. ornus is a host of H. fraxineus, that the fungus’s occurrence on this ash species is presumably limited to leaves, on which it can complete its life cycle, and that its impact on flowering ash may be low. F. ornus is considered to be a highly resistant or tolerant host of H. fraxineus, despite it is not known to have undergone co-evolution with this otherwise so damaging invasive alien pathogen.

Keywords: Hymenoscyphus pseudoalbidus, Chalara fraxinea, flowering ash, manna ash, ash dieback.