Experiences of ash dieback in Denmark

Transcription

1 Experiences of ash dieback in Denmark Senior adviser Iben Margrete Thomsen Department of Geosciences and Natural Ressource Management University of Copenhagen Expertmeeting Essentaksterfte, Drachten, NL 18 februari 2015 Essentaksterfte / Ash Dieback Ash dieback is a fungal disease. But does it kill the ash trees? Iben M. Thomsen, University of Copenhagen 1

2 Life cycle of the fungus Chalara fraxinea Hymenoscyphus pseudoalbidus = Hymenoscyphus fraxineus Iben M. Thomsen, University of Copenhagen 2

3 Noodgroei - A sign of desperation High risk of wood discolouration Epicomic shoots on branches and stems NL Febr Iben M. Thomsen, University of Copenhagen 3

4 Necroses of bark and wood discolouration Sted og dato Dias 7 Hymenoscyphusfraxineus Origin: Asia on Fraxinus mandschurica How? Ref: McKinney et al (submitted) Iben M. Thomsen, University of Copenhagen 4

5 Amongst the first to die are pendulate ash Treuressen Sted og dato Dias 9 Amongst the first to die are pendulate ash Treuressen Iben M. Thomsen, University of Copenhagen 5

6 Essentaksterfte / Ash Dieback Katastrofal im Wald / A disaster in forests In der Stadt /offenen Landschaft weniger fatal Less fatal in towns and the open landscape See also slides at the end 2013 Sommer 2013 Winter Iben M. Thomsen, University of Copenhagen 6

7 Fraxinus in Kopenhagen Strassenbäume 8% des Bestands ÜberwiegendF. excelsior 50 % später als 2000 gepflanzt Nicht seit 2012 F. excelsior Allee Keine Symptome Triebe gesund Marts 2014 Possible explanations No honey fungus / honingzwam (Armillaria) No ash bark beetles / Essenbastkever (Hylesinus) Iben M. Thomsen, University of Copenhagen 7

8 Reduzierte Infektion / Reduced infection Laubentfernung / removal of leaf litter Eher Trocken = weniger Fruchtkörper Drier conditions = fewer fruitbodies Stadt- und Straßenbäumen / City and road trees Viele junge Eschen sterben wahrscheinlich. Many young ash trees will probably die. Iben M. Thomsen, University of Copenhagen 8

9 Stadt- und Straßenbäumen / City and road trees Alte Eschen sterben manchmal auch. Old ash trees die occasionally. Aber viele alte Esche überleben But plenty of old ash trees survive Iben M. Thomsen, University of Copenhagen 9

10 2013 Ash dieback outside of forests is an aesthetical problem, not a matter of survival. Saved at the last minute 2014 This huge ash tree in a church yard was scheduled for felling in 2013 du to ash dieback. Instead they did a crown pruning and kept the tree. The old ash will probably live for many years with the disease, showing dieback symptoms in some years and less in others. Repeated pruning every 5 or 10 years will deal with any safety concerns from dead branches. Iben M. Thomsen, University of Copenhagen 10

11 Nicht zu fruh fällen / Don t fell too soon Eschen in Städten, längs Straßen und in der Landschaft so lange wie möglich bewahren (Verkehrssicherheit beachten). Preserve ash trees in cities, along road and in the landscape for as long as possible (keep safety in mind). Die Bäume sollten erst gefällt werden, wenn sie absterben, oder ihre Krone über 2-3 Jahre nicht wieder regenerieren. The trees should be felled when they die, or when they do not regenerate their crowns 2-3 years in a row. Iben M. Thomsen, University of Copenhagen 11

12 Zukunft der Eschen / Future of ash? Resistente Eschen anwenden - wenn sie verfügbar sind. Use resistant species / clones - if or when available Find and clone healthy ash Iben M. Thomsen, University of Copenhagen 12

13 Test resistance against disease Artificial inoculation with H. fraxineus Seed orchard with controlled crossings Iben M. Thomsen, University of Copenhagen 13

14 Conclusions Please do not panic! It is not like Dutch Elm disease, felling trees fast does not prevent spread of fungus. Removing fallen leaves is much better. Sick trees can live many years and look OK, particularly if you remove dead branches. 1-2 % ash are resistant, look out for them. Use Fraxinus ornus or perhaps Fraxinus americana or F. mandschurica IMT, University of Copenhagen Iben M. Thomsen, University of Copenhagen 14

15 2008 IMT, University of Copenhagen 2009 IMT, University of Copenhagen Iben M. Thomsen, University of Copenhagen 15

16 2010 IMT, University of Copenhagen 2011 IMT, University of Copenhagen Iben M. Thomsen, University of Copenhagen 16

17 IMT, University of Copenhagen 2013 IMT, University of Copenhagen Iben M. Thomsen, University of Copenhagen 17

18 Dec 2013 IMT, University of Copenhagen 2014 IMT, University of Copenhagen Iben M. Thomsen, University of Copenhagen 18