<abstract xmlns="http://www.w3.org/1999/xhtml"><p>The weakening and decline of European ash <italic>Fraxinus excelsior</italic> L. and other ash species have been recorded at different locations in the suburbs of Saint Petersburg, Russia. During the summer of 2019 and spring of 2020, samples from leaves, petioles, and shoots were collected from the weakened and declining ash trees in three parks in Pushkin and Gatchina and maintained in humid chambers to induce the fructification of fungi. In total, 30 taxa of micromycetes belonging to 23 genera were identified using methods of light microscopy. <italic>Hymenoscyphus fraxineus</italic>, a putative agent of ash dieback, was not recorded in the samples collected in the crowns of trees, but only on the petioles of the fallen leaves in spring. Out of all the micromycetes recorded, only coelomycetes from the genus <italic>Diplodia</italic> Fr. (in particular, <italic>D. mutila</italic>) can damage the branches of ash trees and, thus, be considered pathogenic. It is likely that <italic>H. fraxineus</italic> opens “the entry of infection” and <italic>Diplodia</italic> spp. cause the major weakening and decline of branches. The data obtained can significantly change our understanding of the causes of ash dieback and possible methods of ash stand preservation. The reason for the low pathogenicity and activity of <italic>H. fraxineus</italic>, as well as the possible role of ascomycetes <italic>Diplodia</italic> spp. in the dieback of ash stands requires further research.</p></abstract>

The weakening and decline of European ash Fraxinus excelsior L. and other ash species have been recorded at different locations in the suburbs of Saint Petersburg, Russia. During the summer of 2019 and spring of 2020, samples from leaves, petioles, and shoots were collected from the weakened and declining ash trees in three parks in Pushkin and Gatchina and maintained in humid chambers to induce the fructification of fungi. In total, 30 taxa of micromycetes belonging to 23 genera were identified using methods of light microscopy. Hymenoscyphus fraxineus, a putative agent of ash dieback, was not recorded in the samples collected in the crowns of trees, but only on the petioles of the fallen leaves in spring. Out of all the micromycetes recorded, only coelomycetes from the genus Diplodia Fr. (in particular, D. mutila) can damage the branches of ash trees and, thus, be considered pathogenic. It is likely that H. fraxineus opens “the entry of infection” and Diplodia spp. cause the major weakening and decline of branches. The data obtained can significantly change our understanding of the causes of ash dieback and possible methods of ash stand preservation. The reason for the low pathogenicity and activity of H. fraxineus, as well as the possible role of ascomycetes Diplodia spp. in the dieback of ash stands requires further research.

Decline of <italic>Fraxinus excelsior</italic> L. in parks of Saint Petersburg: Who is to blame – <italic>Hymenoscyphus fraxineus</italic> or <italic>Diplodia</italic> spp.?

Department of Forest Protection, Wood Science and Game Management

Saint Petersburg State Forest Technical University

Department of Biogeography and Environmental Protection

Forestry Studies

This work is licensed under the Creative Commons Attribution 4.0 International License.

Decline of  L. in parks of Saint Petersburg: Who is to blame –  or  spp.?

The weakening and decline of European ash Fraxinus excelsior L. and other ash species have been recorded at different locations in the suburbs of Saint...

Decline of Fraxinus excelsior L. in parks of Saint Petersburg: Who is to blame – Hymenoscyphus fraxineus or Diplodia spp.?

Article Category: Research paper

Published Online: Mar 11, 2021

Page range: 43 - 51

Received: May 11, 2020

Accepted: Nov 23, 2020

DOI: https://doi.org/10.2478/fsmu-2020-0013

Keywords
ash dieback, European ash, Ascomycota, tree health, invasive tree fungal pathogen, urban greening

© 2020 Dmitrii A. Shabunin et al., published by Sciendo

This work is licensed under the Creative Commons Attribution 4.0 International License.

Decline of Fraxinus excelsior L. in parks of Saint Petersburg: Who is to blame – Hymenoscyphus fraxineus or Diplodia spp.?

Article Category: Research paper

Published Online: Mar 11, 2021

Page range: 43 - 51

Received: May 11, 2020

Accepted: Nov 23, 2020

DOI: https://doi.org/10.2478/fsmu-2020-0013

Keywordsash dieback, European ash, Ascomycota, tree health, invasive tree fungal pathogen, urban greening

© 2020 Dmitrii A. Shabunin et al., published by Sciendo

This work is licensed under the Creative Commons Attribution 4.0 International License.

Keywords
ash dieback, European ash, Ascomycota, tree health, invasive tree fungal pathogen, urban greening