biology of chalara fraxinea: identification and reporting of infected trees

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


Wider Environment

Newly Planted/Nurseries



Wider Environment



Ash Dieback Locations28 May 2013

Wider Environment




Wider Environment



Ash Dieback Locations16 June 2014

Wider Environment


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



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


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


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


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

http://www.opalexplorenature.org/

http://www.treezilla.org/

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)

– [email protected]

• 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

http://www.forestry.gov.uk/chalara

mailto:[email protected]

http://www.fera.defra.gov.uk/

http://www.sylva.org.uk/treewatch

http://www.opalexplorenature.org/TreeSurvey

http://ashtag.org/

http://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