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LAP Ash Dieback Workshop
The biology of Hymenoscyphus fraxineus:
identification and reporting of infected trees
Edward Wil...
Outline
• Introduction
– Threats to forests
– History of Chalara ash dieback disease spread
• Biology of Hymenoscyphus fra...
Threats to UK Forests
Source: Forestry Commission England 2012
• Climate change
– Summer droughts increasingly likely, esp...
25th July 2012
Which tree species to plant for a changing
environment
Biosecurity of Trees in Britain: Chalara ash dieback...
2010 2011
2005
20062002
2009
2003
2002
2011
2012
2012
Decade of Contagion?
Source: Barnaby Wylder 2013
History of Hymenoscyphus fraxineus
(formerly Chalara fraxinea)
Date Event/Comment
1992 New lethal disease of ash observed ...
Ash dieback disease – Chalara fraxinea
Natural range of ash (Fraxinus excelsior) in Europe
Dates indicate the spread of in...
Source: Barnaby Wylder, Forestry Commission 2012
Ash Dieback in Denmark
Photo: Mari Jonsson,
Swedish University of Agricultural Sciences
Ash Dieback in Sweden
Chalara ash dieback in Europe –
Hymenoscyphus fraxineus
 Vascular wilt fungus
 Pleomorphic (two stage life cycle)
 Emer...
There appears to be variation among Fraxinus spp.
in resistance or tolerance to Hymenoscyphus fraxineus
Highly susceptible...
Chalara Ash Dieback Disease
(Hymenoscyphus fraxineus)
• February 2012
– consignment of seedlings
from Netherlands to the
U...
• November 2012 –
– Cobra Committee Meets
– Rapid action national survey
– Recognition of 2 possible routes
of disease tra...
Ash in the UK
Source: Forestry Commission 2013
Ash in the UK:
• 142K Ha
• 11 % of broadleaves
• 14 % of standing
broadleaf...
Ash Dieback Locations
6 November 2012
Source: Forestry Commission
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations
22 November 2012
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations
28 May 2013
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations
11 November 2013
Wider Environment
Newly Planted/Nurseries
Source: Forestry Commission
Ash Dieback Locations
16 June 2014
Wider Environment
Newly Planted/Nurseries
Confirmed reports of Chalara ash dieback (Hymenoscyphus fraxineus) in the UK
1 November 2012 to 6 October 2014
Data: Fores...
Ash Dieback Locations
03 August 2015
After October 2014, the Forestry
Commission adopted a new
approach to reporting the l...
LATEST SITUATION
Ash Dieback Locations
03 April 2017
After October 2014, the Forestry
Commission adopted a new
approach to...
Proposed Map of
Important Ash Locations
Source: Interim Chalara Control Plan, Defra 2012
Areas with widespread Chalara
inf...
The progress and spread of Chalara dieback of ash is most advanced in Suffolk and Norfolk.
Here natural regeneration estab...
The progress and spread of Chalara dieback of ash is most advanced in Suffolk and Norfolk. Here a group
of pole-stage tree...
Anatomy of an ash leaf
Compound leaf
Leaflet
Blade
Midrib
Rachis
Petiolule
Petiole
Photo: E. R. Wilson 2013
Model for the invasion and spread strategy
of H. fraxineus in the woody sprout
1. Ascospore state
2. Spore germination or ...
Ash dieback – a foliar disease
Images courtesy of I Thomsen and L McKinney
Image Stina Bengtsson
Lifecycle of Hymenoscyphu...
Ascocarps (fruiting bodies) on the rachis of a decaying ash
leaf from the previous growing season.
11 August 2015, Pound F...
Spore release of Hymenoscyphus fraxineus
Spore numbers at night Spore numbers at 5am Spore numbers at 7am
Work of Halvor S...
Spotting Chalara ash dieback
• Check ash plantations and
woodlands regularly during the
growing season for signs of
Chalar...
Signs of disease
Source: Barnaby Wylder, Forestry Commission 2012Source: Forest Research
Diamond-shaped lesions at branch ...
Source: Forestry Commission
Wilting leaves from early summer onwards Fruiting bodies on rachis of decaying leaves
Signs of...
Trace Forward: Recently planted seedling showing
signs of ash dieback disease (Hymenoscyphus fraxineus).
Note 1. dieback o...
Early signs of ash dieback disease (Hymenoscyphus fraxineus) on young coppice shoots,
Frithy Wood, Suffolk (Green Light Tr...
Dieback on shoots (2013) and wilting leaves (2014), signs of ash dieback disease
(Hymenoscyphus fraxineus), Frithy Wood, L...
Dieback on shoots of pole-stage ash. Note the different pattern of dieback on adjacent trees.
Golden Wood (Green Light Tru...
Different patterns of ash dieback on adjacent trees, Frithy Wood (Green Light Trust), Lawshall, Suffolk.
At advanced stage...
Where there are high
spore densities it is
possible to see basal
lesions associated with
direct infection of the
stem.
Les...
Photo: E. R. Wilson 2013
Other things we need to be aware of with Ash trees
Ash tress by the River Eamont, Cumbria
There a...
There is often significant variation in flushing dates
Two veteran ash trees in Cumbria, 19 May 2014
(approximately 200 m ...
Dasineura fraxini
the ash midrib gall midge Photo: E. R. Wilson 2013
Photograph courtesy of Nigel Straw, Forest Research
The ash bud moth Prays fraxinella,
is a native micromoth.
Ash key gall...
Nectria canker is caused by the
fungus Neonectria galligena.
Emerald Ash Borer (Agrilus
planipennis) is currently NOT
pres...
Emerald ash borer on leaf of American white ash, Fraxinus americana. Toronto, Ontario,
Canada. Photo: E. R. Wilson 17 June...
Emerald ash borer. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015
Emerald Ash Borer – Most Unwanted!
Not prese...
Emerald ash borer damage to American white ash, Fraxinus americana. Toronto, Ontario,
Canada. Photo: E. R. Wilson 17 June ...
Emerald ash borer damage to American white ash, Fraxinus americana. Note the larval frass
trails in what was the cambium l...
Emerald ash borer damage to American white ash, Fraxinus americana.
Scarborough neighbourhood, Toronto, Ontario, Canada. P...
Emerald ash borer damage to American white ash, Fraxinus americana.
Scarborough neighbourhood, Toronto, Ontario, Canada. P...
A high profile public awareness and education programme is being delivered by the
Forestry Department at the Town of Oakvi...
The Forestry Department at the Town of Oakville is highly engaged with researchers and
collecting data on EAB population d...
Summary
• Forest pests and diseases are a major issue in Britain and elsewhere
(Globalisation, Climate change)
• Chalara a...
livingashproject.org.uk
Project partners:
LAP Ash Dieback Workshop
Acknowledgements
My thanks to the following colleagues: Ben Jones and Barnaby Wylder, Forestry
Co...
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Biology of Chalara Ash Dieback Disease (June 2017)

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Presentation on the biology of Chalara ash dieback disease (Hymenoscyphus fraxineus). Presented at the Living Ash Project Workshop, Grassington, North Yorkshire, 8 June 2017.

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Biology of Chalara Ash Dieback Disease (June 2017)

  1. 1. LAP Ash Dieback Workshop The biology of Hymenoscyphus fraxineus: identification and reporting of infected trees Edward Wilson Silviculturist Chalara Ash Dieback Workshop Yorkshire Dales National Park Town Hall, Grassington, North Yorkshire 08 June 2017 First presented: 18 06 2014 This version: v3.0, 08 06 2017
  2. 2. Outline • Introduction – Threats to forests – History of Chalara ash dieback disease spread • Biology of Hymenoscyphus fraxineus – Formerly called Chalara fraxinea • Identification (picture guide) • Recognising other threats and reporting infected trees
  3. 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. 4. 25th July 2012 Which tree species to plant for a changing environment Biosecurity of Trees in Britain: Chalara ash dieback disease is only the latest on a growing list of nasty pests/pathogens Source: Forestry Commission 2012
  5. 5. 2010 2011 2005 20062002 2009 2003 2002 2011 2012 2012 Decade of Contagion? Source: Barnaby Wylder 2013
  6. 6. History of Hymenoscyphus fraxineus (formerly 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. 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 2012
  8. 8. Source: Barnaby Wylder, Forestry Commission 2012 Ash Dieback in Denmark
  9. 9. Photo: Mari Jonsson, Swedish University of Agricultural Sciences Ash Dieback in Sweden
  10. 10. Chalara ash dieback in Europe – Hymenoscyphus fraxineus  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
  11. 11. There appears to be variation among Fraxinus spp. in resistance or tolerance to Hymenoscyphus fraxineus Highly susceptible Fraxinus excelsior Fraxinus angustifolia Fraxinus niger Moderately susceptible Fraxinus ornus Fraxinus pennsylvanica Least susceptible Fraxinus americana Fraxinus mandschurica
  12. 12. Chalara Ash Dieback Disease (Hymenoscyphus fraxineus) • February 2012 – consignment of seedlings from Netherlands to the UK found to be infected with Hymenoscyphus fraxineus • October 2012 – Fera confirmed first cases in “wider environment” – Note: now thought likely that the disease arrived in the UK at an earlier datePhoto: Forestry Commission 2012
  13. 13. • November 2012 – – Cobra Committee Meets – Rapid action national survey – Recognition of 2 possible routes of disease transfer to the UK: • airborne from western Europe • Importation of infected seedlings – Tree Health surveys initiated • (FC staff and trained contract surveyors) Photo: Forestry Commission 2012 Chalara Ash Dieback Disease (Hymenoscyphus fraxineus)
  14. 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. 15. Ash Dieback Locations 6 November 2012 Source: Forestry Commission Wider Environment Newly Planted/Nurseries
  16. 16. Source: Forestry Commission Ash Dieback Locations 22 November 2012 Wider Environment Newly Planted/Nurseries
  17. 17. Source: Forestry Commission Ash Dieback Locations 28 May 2013 Wider Environment Newly Planted/Nurseries
  18. 18. Source: Forestry Commission Ash Dieback Locations 11 November 2013 Wider Environment Newly Planted/Nurseries
  19. 19. Source: Forestry Commission Ash Dieback Locations 16 June 2014 Wider Environment Newly Planted/Nurseries
  20. 20. Confirmed reports of Chalara ash dieback (Hymenoscyphus fraxineus) in the UK 1 November 2012 to 6 October 2014 Data: Forestry Commission 2012-2014 Graphic: AshStat/Silviculture ResearchInternational 2014www.silviculture.org.uk D J F M AN M J J A S O N D J F M A M J A SJ O 2012 2013 2014 0 100 200 300 400 500 600 700 800 900 0 100 200 300 400 500 600 700 CumulativeConfirmedReports Days from Start of Outbreak Nursery Sites Recently Planted Sites Wider Environment Total
  21. 21. Ash Dieback Locations 03 August 2015 After October 2014, the Forestry Commission adopted a new approach to reporting the location of infected areas, based on timing of confirmed site(s) within 10 km grids. Note: The map reflects both the spread of infection, and the effectiveness of monitoring and detection.
  22. 22. LATEST SITUATION Ash Dieback Locations 03 April 2017 After October 2014, the Forestry Commission adopted a new approach to reporting the location of infected areas, based on timing of confirmed site(s) within 10 km grids. Note: The map reflects both the spread of infection, and the effectiveness of monitoring and detection.
  23. 23. Proposed Map of Important Ash Locations Source: Interim Chalara Control Plan, Defra 2012 Areas with widespread Chalara infection and where the disease was first established in the wider environment. Ash remains an important feature in the NW and North Yorks landscape and within woodland ecosystems.
  24. 24. The progress and spread of Chalara dieback of ash is most advanced in Suffolk and Norfolk. Here natural regeneration established from 2005 is now infected and there is significant mortality. This site is being monitored to see if there are any resistant trees. Suffolk Wildlife Trust, Suffolk. Photo: E. R. Wilson 11 August 2015
  25. 25. The progress and spread of Chalara dieback of ash is most advanced in Suffolk and Norfolk. Here a group of pole-stage trees has largely died with a few specimens dying back at a slower rate. Pound Farm, Woodland Trust, Suffolk. Photo: E. R. Wilson 11 August 2015
  26. 26. Anatomy of an ash leaf Compound leaf Leaflet Blade Midrib Rachis Petiolule Petiole Photo: E. R. Wilson 2013
  27. 27. Model for the invasion and spread strategy of H. fraxineus in the woody sprout 1. Ascospore state 2. Spore germination or initial mycelium (leaves and petioles) 3. Spread inside wood (longitudinal: pith, vessels and fibres; radial: rays) 4. Cambium and bark necrosis (l) as well as comparable stage after natural infection in the host (r). Source: Schumacher 2011
  28. 28. Ash dieback – a foliar disease Images courtesy of I Thomsen and L McKinney Image Stina Bengtsson Lifecycle of Hymenoscyphus fraxineus H. fraxineus fruit bodies on fallen ash rachises produce ascospores
  29. 29. Ascocarps (fruiting bodies) on the rachis of a decaying ash leaf from the previous growing season. 11 August 2015, Pound Farm, Suffolk. Photo: E. R. Wilson
  30. 30. 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
  31. 31. Spotting Chalara ash dieback • Check ash plantations and woodlands regularly during the growing season for signs of Chalara ash dieback disease • Look for: – leaf wilting and premature browning in the growing season – Shoot dieback and epicormic sprouting – Characteristic diamond- shaped lesions on stems at branch unions • Check current guidance for disease signs and symptoms – see www.forestry.gov.uk/chalara Photo: E. R. Wilson 2014 Photo: E. R. Wilson 2014Photo: Forest Research
  32. 32. Signs of disease Source: Barnaby Wylder, Forestry Commission 2012Source: Forest Research Diamond-shaped lesions at branch unions Rapid dieback of branches and stems
  33. 33. Source: Forestry Commission Wilting leaves from early summer onwards Fruiting bodies on rachis of decaying leaves Signs of disease
  34. 34. Trace Forward: Recently planted seedling showing signs of ash dieback disease (Hymenoscyphus fraxineus). Note 1. dieback on shoots 2. lesions at branch unions 3. epicormic/adventitious shoot development in current year Photo: Sharon Rodhouse 2012
  35. 35. Early signs of ash dieback disease (Hymenoscyphus fraxineus) on young coppice shoots, Frithy Wood, Suffolk (Green Light Trust). Photo: E. R. Wilson 17 June 2014
  36. 36. Dieback on shoots (2013) and wilting leaves (2014), signs of ash dieback disease (Hymenoscyphus fraxineus), Frithy Wood, Lawshall, Suffolk. Photo: E. R. Wilson 17 June 2014
  37. 37. 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
  38. 38. 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
  39. 39. Where there are high spore densities it is possible to see basal lesions associated with direct infection of the stem. Lesions due to Hymenoscyphus fraxineus on the stem of pole-stage ash Photo: J. Clark 2014
  40. 40. Photo: E. R. Wilson 2013 Other things we need to be aware of with Ash trees Ash tress by the River Eamont, Cumbria There are two ash trees in this picture – one bearing seed (Tree 1 – FEMALE) and the other not (Tree 2 – MALE). Remember ash keys (samaras) are borne in clusters through winter and should not be confused with signs of dieback.. Tree 1 Tree 2
  41. 41. 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
  42. 42. Dasineura fraxini the ash midrib gall midge Photo: E. R. Wilson 2013
  43. 43. 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
  44. 44. Nectria canker is caused by the fungus Neonectria galligena. Emerald Ash Borer (Agrilus planipennis) is currently NOT present in UK. Source: OPAL
  45. 45. Emerald ash borer on leaf of American white ash, Fraxinus americana. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015 Emerald Ash Borer – Most Unwanted! Not present in the UK at present time; risk of future introduction
  46. 46. Emerald ash borer. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015 Emerald Ash Borer – Most Unwanted! Not present in the UK at present time; risk of future introduction
  47. 47. Emerald ash borer damage to American white ash, Fraxinus americana. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015
  48. 48. Emerald ash borer damage to American white ash, Fraxinus americana. Note the larval frass trails in what was the cambium layer inside the bark. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015
  49. 49. Emerald ash borer damage to American white ash, Fraxinus americana. Scarborough neighbourhood, Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015
  50. 50. Emerald ash borer damage to American white ash, Fraxinus americana. Scarborough neighbourhood, Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015
  51. 51. A high profile public awareness and education programme is being delivered by the Forestry Department at the Town of Oakville. Here we see adverts placed on local buses. Town of Oakville, Ontario, Canada. Photo: E. R. Wilson 16 June 2015
  52. 52. The Forestry Department at the Town of Oakville is highly engaged with researchers and collecting data on EAB population dynamics, in partnership with other agencies, including the Ontario Ministry of Natural Resources and the Canadian forest Service. Here we see a pheromone trap being installed in an ash tree. Town of Oakville, Ontario, Canada. Photo: E. R. Wilson 16 June 2015
  53. 53. Summary • Forest pests and diseases are a major issue in Britain and elsewhere (Globalisation, Climate change) • Chalara ash dieback disease has spread across the range of ash in Britain • Vascular wilt fungus with aerial ascospores, difficult to treat/control • Signs and Symptoms (lesions, leaf wilt, epicormics and evidence of ascospores on rachi) • Many other threats to ash, non-lethal and lethal – Vigilance is important with respect to potential introduction of emerald ash borer • Public engagement is important in managing tree health issues and newly introduced threats • Further Information: https://www.forestry.gov.uk/pestsanddiseases • Reporting tree health issues: www.forestry.gov.uk/treealert
  54. 54. livingashproject.org.uk Project partners:
  55. 55. 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@rfs.org.uk First presented: 18 06 2014 This version: v3.0, 08 06 2017

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