LAP Ash Dieback Workshop
The biology of Chalara fraxinea:
identification and reporting of infected trees
Edward WilsonSilviculturist
Chalara Ash Dieback Workshop
Lawshall Village Hall, Lawshall, Suffolk
18 June 2014
First presented: 18 06 2014This version: v1.1, 02 07 2014
RESEARCH
I N T E R N A T I O N A L
Outline
• Introduction
• Biology of Chalara fraxinea
– now correctly called Hymenoscyphus fraxineus
• Identification (picture guide)
• Reporting (potentially) infected trees
• Questions and Discussion
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
25th July 2012Which 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
2010 2011
2005
20062002
2009
2003
2002
20112012
2012
Decade of Contagion?
Source: Barnaby Wylder 2013
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
Ash dieback disease – Chalara fraxineaNatural 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
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
There appears to be variation among Fraxinus spp. in resistance or tolerance to Chalara fraxinea
Highly susceptibleFraxinus excelsior
Fraxinus angustifolia
Fraxinus niger
Moderately susceptibleFraxinus ornus
Fraxinus pennsylvanica
Least susceptibleFraxinus americana
Fraxinus mandschurica
Source: Barnaby Wylder, Forestry Commission 2012
Ash Dieback in Denmark
Photo: Mari Jonsson, Swedish University of Agricultural Sciences
Ash Dieback in Sweden
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
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
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
Ancient woodlands and trees in Borrowdale, CumbriaRecognising ash as an important component in many woodland types
Photo: E. R. Wilson 2012
Ash pollard Near Glaramara, Borrowdale, CumbriaPhoto: E.R. Wilson 2012
Ash in the landscape outside woodlandsImportant ecological and cultural values
Ash pollard Near Rosthwaite, Borrowdale, Cumbria Photo: E.R. Wilson 2012
Review of Ecological Implications of Chalara ash dieback in Britain (2014)
• 953 species “associated” with ash:
– 12 birds, 28 mammals, 58 bryophytes, 68 fungi, 239 invertebrates, 548 lichens
• 62 species were “highly associated” species
• 44 “obligate” species:
– 11 fungi, 29 invertebrates, 4 lichen
• Reference:
– Mitchell, R.J., et al. 2014. Conservation Biology 175: 95-109
Ash Dieback Locations6 November 2012
Source: Forestry Commission
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations22 November 2012
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations28 May 2013
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations11 November 2013
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations16 June 2014
Wider Environment
Newly Planted/Nurseries
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 UK1 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
Anatomy of an ash leaf
Compund leaf
Leaflet
Blade
Midrib
Rachis
Petiolule
Petiole
Photo: E. R. Wilson 2013
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.
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
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
Source: Forestry Commission
Wilting leaves from early summer onwards Fruiting bodies on rachis of decaying leaves
Signs of disease
Signs of disease
Source: Barnaby Wylder, Forestry Commission 2012 Source: Forest Research
Diamond-shaped lesions at branch unions Rapid dieback of branches and stems
Trace Forward: Recently planted seedling showingsigns 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
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
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
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
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.
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
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
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
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
Where there are high spore densities it is possible to see basal lesions associated with direct infection of the stem.
Lesions due to Chalara fraxineaon the stem of pole-stage ash
Photo: J. Clark 2014
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
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
Dasineura fraxinithe ash midrib gall midge
Photo: E. R. Wilson 2013
Photograph courtesy of Nigel Straw, Forest ResearchThe ash bud moth Prays
fraxinella, is a native micromoth.Ash key gall caused by the
eriophyid mite Aceria fraxinivora.
Source: OPAL
Nectria canker is caused by the fungus Neonectria galligena.
Emerald Ash Borer (Agrilusplanipennis) is currently NOT
present in UK.
Source: OPAL
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
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.
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
Photo: E. R. Wilson 2013Citizen Science – a group of ash tree surveyors at a training event in Eden District, Cumbria, 5 October 2013
Further Information
• Forestry Commission
– www.forestry.gov.uk/chalara
– 08459 33 55 77 (open 8am - 6pm every day)
• 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
livingashproject.org.ukProject partners:
Ash pollard St John’s in the Vale, Cumbria Photo: E.R. Wilson 2012
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: [email protected]
Web: www.silviculture.org.uk
First presented: 18 06 2014This version: v1.1, 02 07 2014
RESEARCH
I N T E R N A T I O N A L