We studied the influence of the fungus Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz & Hosoya on flowering ash (Fraxinus ornus L.). We were interested in whether the fungus causes damage typical of ash dieback on flowering ash. The presence of the fungus in flowering ash was checked in two different ways, by checking the presence of apothecia of the fungus H. fraxineus on fallen leaf petioles and by isolating fungi from necrotic shoots. The field research was carried out on five sites of flowering ash in Zasavje. The presence of apothecia in leaf litter was checked on 24th and 26th of June 2020 at these locations. We did not detect any apothecia, so we collected 30 petioles of flowering ash in the leaf litter at each location and then incubate them on wet paper in glass petri dishes. Monitoring of apothecia development was performed from 28. 6. 2020 to 7. 8. 2020 at temperatures between 22 ␃ and 24 ␃. Apothecia did not develop on the leaf petioles. Fungi isolations were performed from seven samples of necrotic shoots of flowering ash and from three control samples of common ash (Fraxinus excelsior L.). In total, we obtained seven different fungal morphotypes. Molecular analysis of the obtained morphotypes showed the following fungi species: Pezicula sp., Cytospora sp., Eutypa sp., Eutypa lata, Phomopsis sp., Didymella macrostoma and Biscogniauxia nummularia. Isolation of H. fraxineus from the obtained fungi isolates was unsuccessful. We concluded that the fungi with the best potential to cause damage on flowering ash were Phomopsis sp. and Biscogniauxia nummularia. Although the presence of H. fraxineus on flowering ash was not confirmed, we cannot conclude that the fungus did not cause damage to the flowering ash in selected locations.
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