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

Dmitrii A. Shabunin
Dmitrii A. Shabunin
, 
Andrey V. Selikhovkin
Andrey V. Selikhovkin
, 
Elena Yu. Varentsova
Elena Yu. Varentsova
 and 
Dmitry L. Musolin
Dmitry L. Musolin
   | Mar 11, 2021
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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
© 2020 Dmitrii A. Shabunin et al., published by Sciendo
This work is licensed under the Creative Commons Attribution 4.0 International License.

Figure 1

Location of the parks surveyed in this study.
Location of the parks surveyed in this study.

Figure 2

Group weakening and decline of European ash Fraxinus excelsior trees in Babolovsky Park (photo by Bui Dinh Duc, with permission).
Group weakening and decline of European ash Fraxinus excelsior trees in Babolovsky Park (photo by Bui Dinh Duc, with permission).

Figure 3

Typical appearance of European ash Fraxinus excelsior of the health category III (heavily weakened trees) from which samples were collected for the identification of pathogenic micromycetes (Aleksandrovsky Park, Pushkin; photo by Andrey V. Selikhovkin).
Typical appearance of European ash Fraxinus excelsior of the health category III (heavily weakened trees) from which samples were collected for the identification of pathogenic micromycetes (Aleksandrovsky Park, Pushkin; photo by Andrey V. Selikhovkin).

Figure 4

Conidia (left), conidia and conidiophores (right) of Diplodia mutila (Fr.) Mont. from shoots of Fraxinus excelsior collected on July 25, 2019 in Aleksandrovsky Park, Pushkin (left) and Palace Park, Gatchina (right) (photo by Dmitrii A. Shabunin).
Conidia (left), conidia and conidiophores (right) of Diplodia mutila (Fr.) Mont. from shoots of Fraxinus excelsior collected on July 25, 2019 in Aleksandrovsky Park, Pushkin (left) and Palace Park, Gatchina (right) (photo by Dmitrii A. Shabunin).

Micromycetes from the leaves, petioles, and shoots of Fraxinus excelsior cultivated in a humidified incubator.

Date of sample collectionLocation of sampling and identified micromycetes
Aleksandrovsky ParkBabolovsky ParkPalace Park
June 26, 2019*Codinaea sp.*Phomopsis sp.*Stachybotrys sp.*Coniothyrium sp.
***Diplodia mutila (Fr.) Mont.***Diplodia mutila (Fr.) Mont.
July 25, 2019*Cladosporium herbarum (on galls of Dasineura fraxinea)*Cladosporium herbarum (on galls of Dasineura fraxinea)*Phyllactinia fraxini (DC.) Fuss*Cladosporium herbarum (on galls of Dasineura fraxinea)*Coniothyrium sp.*Trichothecium roseum (Pers.) Link.**Marasmius sp.**Phomopsis scobina (Cooke) Höhn.
***Diplodia mutila (Fr.) Mont.***Hypoxylon fraxinophilum Pouzar.***Coniothyrium sp.***Diplodia mutila (Fr.) Mont.***Trichothecium roseum (Pers.) Link.
August 27, 2019*Alternaria sp.*Botrytis sp. (B. cinerea?)*Cladosporium spp.*Gonatobotrys flava Bonord.*Hansfordia sp.*Harsia sp.*Periconia cookei E.W. Mason et M.B. Ells*Periconia sp.*Phomopsis scobina (Cooke) Höhn.*Stachybotrys sp.*Trichothecium roseum (Pers.) Link.*Phyllactinia guttata*Alternaria sp.*Cladosporium spp.*Gliomastix sp.*Periconia sp.*Phomopsis scobina (Cooke) Höhn.*Phyllactinia sp. (possibly, P. guttata)
***Diplodia sp.***Gliomastix sp.***Diplodia sp.***Cytospora pruinosa (Fr.) Sacc.***Trichoderma sp.***Diplodia sp.***Stachybotrys sp.***Trichoderma sp.
May 27, 2020**Alternaria spp.**Cladosporium sp.**Fusicladium fraxini Aderh.**Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz & Hosoya**Alternaria sp.**Cladosporium macrocarpum Preuss**Cladosporium sp.**Coniothyrium sp.**Dictyochaeta sp.**Fusicladium fraxini Aderh.**Gyrothrix ramosa Zucconi & Onofri**Hymenoscyphus fraxineus (T. Kowalski) Baral, Queloz & Hosoya**Periconia cookei E.W. Mason & M.B. Ellis**Periconia sp.

The health state of Fraxinus excelsior trees in the parks of Pushkin and Gatchina according to the surveys of 2018–2019.

Health state categories of treesScoreNumber of trees in each category for each park (%)
Aleksandrovsky ParkBabolovsky ParkPalace Park
I (healthy trees)10 (0.0)0 (0.0)0 (0.0)
II (weakened trees)25 (13.5)3 (8.6)16 (18.2)
III (heavily weakened trees)320 (54.1)12 (34.3)54 (61.4)
IV (drying-out trees)410 (27.0)15 (42.8)15 (17.0)
V (trees that had died during the current year) and VI (trees that had died during the previous year) combined5 and 62 (5.4)5 (14.3)3 (3.4)
Total37 (100)35 (100)88 (100)
Weighted score of the tree health category3.253.703.07
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