This presentation was prepared for the Living Ash Project Chalara Ash Dieback Workshop at Lawshall, Suffolk on 18 June 2014.
The talk aims to provide an overview of the history and biology of Chalara ash dieback in Britain, and focuses on the lifecycle, signs and symptoms of infection. Additional information is provided regarding current research programmes on ash dieback disease, the genetics of ash (Fraxinus excelsior) and arrangements for reporting suspected cases of infection. The presentation includes many photographs taken in the field and supplied with acknowledgement by colleagues.
Further information on the Living Ash Project is available at www.livingashproject.org.uk. Also at the Future Trees Trust, www.futuretrees.org. General information about the biology of Chalara ash dieback is available from the Forestry Commission, www.forestry.gov.uk/chalara.
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Biology of Chalara fraxinea: identification and reporting of infected trees
1. LAP Ash Dieback Workshop
The biology of Chalara fraxinea:
identification and reporting of infected trees
Edward Wilson
Silviculturist
Chalara Ash Dieback Workshop
Lawshall Village Hall, Lawshall, Suffolk
18 June 2014
First presented: 18 06 2014
This version: v1.1, 02 07 2014
RESEARCH
I N T E R N A T I O N A L
2. Outline
• Introduction
• Biology of Chalara fraxinea
– now correctly called Hymenoscyphus fraxineus
• Identification (picture guide)
• Reporting (potentially) infected trees
• Questions and Discussion
3. Threats to UK Forests
Source: Forestry Commission England 2012
• Climate change
– Summer droughts increasingly likely, especially in South and East
– Extreme rain and flooding events are more likely
– Ecosystem change – especially ground plants
• Pests and diseases
– Native and exotic
• Low Resilience of Existing Forest Resources
– Low number of productive species
• England – Conifers > 5 species = 88% of area
• England – Broadleaves > 5 species = 72% of area
– Monoculture stands are most common
4. 25th July 2012
Which tree species to plant for a changing
environment
Biosecurity of Trees in Britain: Ash dieback disease is only the
latest on a growing list of nasty pests/pathogens
Source: Forestry Commission 2012
6. History of Chalara fraxinea
Date Event/Comment
1992 New lethal disease of ash observed in Poland
1992 - Spread to other regions in Europe; causal agent unclear
Early 2000s A Chalara fungus isolated from many infected trees
2006 Asexual state of the fungus identified and named Chalara
fraxinea
Sexual state thought to be Hymenoscyphus albidus, a wide-
spread and previously non-lethal fungus on ash
2010 Molecular research later confirmed the sexual state is a new
species, Hymenoscyphus pseudoalbidus
May 2014 Revised nomenclature for the fungus has led to new name,
Hymenoscyphus fraxineus
7. Ash dieback disease – Chalara fraxinea
Natural range of ash (Fraxinus excelsior) in Europe
Dates indicate the spread of infection across Europe, with the earliest
cases being confirmed in Poland (1992). Map; EUFORGEN
8. Ash dieback in Europe – Chalara fraxinea
Vascular wilt fungus
Pleomorphic (two stage life cycle)
Emerged as an entirely new
disease in Europe in the 1990s
Initially cause was unknown –
frost and drought both implicated
in dieback symptoms
Early impact Poland, Lithuania,
Latvia, then Scandinavian
countries
Some countries 60-90% ash affected
eg Denmark since 2009.
Despite impact & spread, not
designated as quarantine
organism
Source: Forestry Commission
9. There appears to be variation among Fraxinus spp.
in resistance or tolerance to Chalara fraxinea
Highly susceptible
Fraxinus excelsior
Fraxinus angustifolia
Fraxinus niger
Moderately susceptible
Fraxinus ornus
Fraxinus pennsylvanica
Least susceptible
Fraxinus americana
Fraxinus mandschurica
12. Ash Dieback Disease
(Chalara fraxinea)
• February 2012
– consignment of seedlings
from Netherlands to the
UK found to be infected
with Chalara fraxinea
• October 2012
– Fera confirmed first cases
in “wider environment”
– Note: now thought likely
that the disease arrived in
the UK at an earlier date
Photo: Forestry Commission 2012
13. Ash Dieback Disease
(Chalara fraxinea)
• November 2012 –
– Cobra Committee Meets
– National Survey
– Recognition of 2 possible routes
of disease transfer to the UK:
• airborne from western Europe
• Importation of infected seedlings
– Trace Forward surveys initiated
• Disease Categories:
– Nursery sites
– Recently planted sites
– Wider environment, e.g.
established woodland
Photo: Forestry Commission 2012
14. Ash in the UK
Source: Forestry Commission 2013
Ash in the UK:
• 142K Ha
• 11 % of broadleaves
• 14 % of standing
broadleaf volume
• Mostly found in mixed
stands
15. Ancient woodlands and trees in Borrowdale, Cumbria
Recognising ash as an important component in many woodland types
Photo: E. R. Wilson 2012
16. Ash pollard
Near Glaramara, Borrowdale, CumbriaPhoto: E.R. Wilson 2012
Ash in the landscape outside woodlands
Important ecological and cultural values
24. 0
100
200
300
400
500
600
700
0 50 100 150 200 250 300 350 400 450 500 550 600
Reports
Days from Start of Outbreak
Nursery Sites Recently Planted Sites
Wider Environment Total
D J F M AN M J J A S O
Confirmed reports of ash dieback disease (Chalara fraxinea) in the UK
1 November 2012 to 16 June 2014
Data: Forestry Commission 2012-2014
Graphic: AshStat/Silviculture Research International 2014www.silviculture.org.uk
N D J F M A M J
25. Anatomy of an ash leaf
Compund leaf
Leaflet
Blade
Midrib
Rachis
Petiolule
Petiole
Photo: E. R. Wilson 2013
26. Photo: E. R. Wilson 2013
Ash is famously late flushing in
spring. However, infection can
occur very early in the season
once leaves start to expand.
27. Ash dieback – a foliar disease
Images courtesy of I Thomsen and L McKinney
Image Stina Bengtsson
Lifecycle of Chalara fraxinea
(Hymenoscyphus fraxineus)
H. fraxineus fruit
bodies on fallen ash
rachises produce
ascospores
28. Spore release of Hymenoscyphus fraxineus
Spore numbers at night Spore numbers at 5am Spore numbers at 7am
Work of Halvor Solheim, Volkmar Timmermann & Isabella Berja, Skog og Landskap, Norway
Early in the morning peaking between 6-8 am during summer
30. Signs of disease
Source: Barnaby Wylder, Forestry Commission 2012Source: Forest Research
Diamond-shaped lesions at branch unions Rapid dieback of branches and stems
31. Trace Forward: Recently planted seedling showing
signs of ash dieback disease (Chalara fraxinea).
Note 1. dieback on shoots 2. lesions at branch unions 3.
epicormic/adventitious shoot development in current year Photo: Sharon Rodhouse 2012
32. Recently planted ash seedlings showing signs of ash
dieback disease (Chalara fraxinea), Golden Wood, Suffolk
(Green Light Trust). Photo: E. R. Wilson 17 June 2014
33. Early signs of ash dieback disease (Chalara fraxinea) on young coppice shoots,
Frithy Wood, Suffolk (Green Light Trust). Photo: E. R. Wilson 17 June 2014
34. Ascocarps (fruiting bodies) on the rachis of a leaf from the 2013 growing season,
at the base of young coppice shoots, Frithy Wood, Suffolk (Green Light Trust).
Photo: E. R. Wilson 17 June 2014
35. Advanced wilting of ash leaves due to ash dieback
disease (Chalara fraxinea). Frithy Wood, Suffolk (Green
Light Trust). Photo: E. R. Wilson 17 June 2014.
36. Dieback on shoots (2013) and wilting leaves (2014), signs of ash dieback disease
(Chalara fraxinea), Frithy Wood, Lawshall, Suffolk. Photo: E. R. Wilson 17 June 2014
37. Dieback on shoots (2013) and wilting leaves (2014), signs of ash dieback disease (Chalara
fraxinea), Golden Wood (Green Light Trust), Lawshall, Suffolk. Photo: E. R. Wilson 17 June 2014
38. Dieback on shoots of pole-stage ash. Note the different pattern of dieback on adjacent trees.
Golden Wood (Green Light Trust), Lawshall, Suffolk. Photo: E. R. Wilson 17 June 2014
39. Different patterns of ash dieback on adjacent trees, Frithy Wood (Green Light Trust), Lawshall, Suffolk.
At advanced stages of infection trees often succumb due to secondary pathogens, especially honey
fungus (Armillaria spp.). Photo: E. R. Wilson 17 June 2014
40. Where there are high
spore densities it is
possible to see basal
lesions associated with
direct infection of the
stem.
Lesions due to
Chalara fraxinea
on the stem of
pole-stage ash
Photo: J. Clark 2014
41. Photo: E. R. Wilson 2013
Ash tress by the River Eamont, Cumbria
There are two ash trees in this picture – one bearing seed (Tree 1) and the
other not (Tree 2). Remember ash keys (samaras) are borne in clusters
through winter and should not be confused with signs of dieback.
Tree 1
Tree 2
42. There is often significant variation in flushing dates:
Two veteran ash trees in Cumbria, 19 May 2014
(approximately 200 m apart)
Photos: E. R. Wilson 2014
44. Photograph courtesy of Nigel Straw, Forest Research
The ash bud moth Prays
fraxinella, is a native micromoth.
Ash key gall caused by the
eriophyid mite Aceria fraxinivora.
Source: OPAL
45. Nectria canker is caused by the
fungus Neonectria galligena.
Emerald Ash Borer (Agrilus
planipennis) is currently NOT
present in UK.
Source: OPAL
46. Strategy and Action for Ash
• National Strategy
– Latest update, late March 2013
– Focus on research, monitoring, diagnosis
– Regulations and international partnerships
– Still gather science information/exploring options for
management/containment
• E.g., Living Ash Project
– Encourage local action
• Community Action and Citizen Science
– Range of programmes being developed
47. Proposed Map of
Important Ash Locations
Silviculture and management
guidance is evolving and will
vary with region and the
prevalence of infected stands.
Source: Interim Chalara Control Plan
Defra 2012
Areas with widespread
Chalara infection and where
the disease is established in
the wider environment.
48. Citizen Science
• A range of projects are underway!
• AshTag – identification/report suspected cases
• First a mobile phone app
• Re-launched as a tree tagging project for mapping and long-term monitoring
• University of East Anglia
• OPAL - Tree Buddy Initiative
• Sponsored by Forest Research
• www.opalexplorenature.org
• Treezilla – map of British trees/ecosystem benefits
• Open University
• www.treezilla.org
• Launch 14 June 2013
• Other projects
• Woodland Trust
• Tree Council
• Local Wildlife Trusts
49. Photo: E. R. Wilson 2013
Citizen Science – a group of ash tree surveyors at a
training event in Eden District, Cumbria, 5 October 2013
50. Further Information
• Forestry Commission
– www.forestry.gov.uk/chalara
– 08459 33 55 77 (open 8am - 6pm every day)
– plant.health@forestry.gsi.gov.uk
• Food and Environment Research Agency (FERA)
– www.fera.defra.gov.uk
• TreeWatch - Sylva Foundation
– www.sylva.org.uk/treewatch
• OPAL – Tree Health Survey
– http://www.opalexplorenature.org/TreeSurvey
• AshTag
– http://ashtag.org/
• Future Trees Trust
– www.futuretrees.org
53. LAP Ash Dieback Workshop
Acknowledgements
My thanks to the following colleagues: Ben Jones and Barnaby Wylder, Forestry
Commission England; Joan Webber, Forest Research; Kate Holl, Scottish Natural
Heritage; Mari Jonsson, Swedish University of Agricultural Sciences; Tom
Brown, Green Light Trust; Jo Clark, Earth Trust; Sharon Rodhouse, Sylvatic Ltd
Further Information
Edward Wilson
Email: ted.wilson@silviculture.org.uk
Web: www.silviculture.org.uk
First presented: 18 06 2014
This version: v1.1, 02 07 2014
RESEARCH
I N T E R N A T I O N A L