The biology of Hymenoscyphus fraxineus: identification and reporting of infected trees. Edward Wilson Silviculturist. LAP Ash Dieback Workshop

Transcription

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: This version: v3.0,

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 Climate change Threats to UK Forests 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 Source: Forestry Commission England 2012

4 Biosecurity of Trees in Britain: Chalara ash dieback disease is only the latest on a growing list of nasty pests/pathogens 25 th July 2012 Which tree species to plant for a changing environment Source: Forestry Commission 2012

5 Decade of Contagion? Source: Barnaby Wylder 2013

6 Date History of Hymenoscyphus fraxineus (formerly Chalara fraxinea) Event/Comment 1992 New lethal disease of ash observed in Poland 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 widespread 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 2012 Dates indicate the spread of infection across Europe, with the earliest cases being confirmed in Poland (1992). Map; EUFORGEN

8 Ash Dieback in Denmark Source: Barnaby Wylder, Forestry Commission 2012

9 Ash Dieback in Sweden Photo: Mari Jonsson, Swedish University of Agricultural Sciences

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 Despite impact & spread, not designated as quarantine organism Source: Forestry Commission

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 Least susceptible Fraxinus ornus Fraxinus pennsylvanica Fraxinus americana Fraxinus mandschurica

12 Chalara Ash Dieback Disease (Hymenoscyphus fraxineus) Photo: Forestry Commission 2012 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 date

13 Chalara Ash Dieback Disease (Hymenoscyphus fraxineus) 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

14 Ash in the UK Ash in the UK: 142K Ha 11 % of broadleaves 14 % of standing broadleaf volume Mostly found in mixed stands Source: Forestry Commission 2013

15 Ash Dieback Locations 6 November 2012 Wider Environment Newly Planted/Nurseries Source: Forestry Commission

16 Ash Dieback Locations 22 November 2012 Wider Environment Newly Planted/Nurseries Source: Forestry Commission

17 Ash Dieback Locations 28 May 2013 Wider Environment Newly Planted/Nurseries Source: Forestry Commission

18 Ash Dieback Locations 11 November 2013 Wider Environment Newly Planted/Nurseries Source: Forestry Commission

19 Ash Dieback Locations 16 June 2014 Wider Environment Newly Planted/Nurseries Source: Forestry Commission

20 Cumulative Confirmed Reports Confirmed reports of Chalara ash dieback (Hymenoscyphus fraxineus) in the UK 1 November 2012 to 6 October N D J F M A M J J A S O N D J F M A M J J A S O Nursery Sites Wider Environment Days from Start of Outbreak Recently Planted Sites Total Data: Forestry Commission Graphic: AshStat/Silviculture Research International 2014

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 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 Proposed Map of Important Ash Locations Ash remains an important feature in the NW and North Yorks landscape and within woodland ecosystems. Areas with widespread Chalara infection and where the disease was first established in the wider environment. Source: Interim Chalara Control Plan, Defra 2012

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 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 Anatomy of an ash leaf Compound leaf Rachis Midrib Blade Petiolule Leaflet Petiole Photo: E. R. Wilson 2013

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 Ash dieback a foliar disease Lifecycle of Hymenoscyphus fraxineus Image Stina Bengtsson H. fraxineus fruit bodies on fallen ash rachises produce ascospores Images courtesy of I Thomsen and L McKinney

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 Spore release of Hymenoscyphus fraxineus Early in the morning peaking between 6-8 am during summer Spore numbers at night Spore numbers at 5am Spore numbers at 7am Work of Halvor Solheim, Volkmar Timmermann & Isabella Berja, Skog og Landskap, Norway

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 diamondshaped lesions on stems at branch unions Check current guidance for disease signs and symptoms see Photo: E. R. Wilson 2014 Photo: Forest Research Photo: E. R. Wilson 2014

32 Signs of disease Diamond-shaped lesions at branch unions Rapid dieback of branches and stems Source: Forest Research Source: Barnaby Wylder, Forestry Commission 2012

33 Signs of disease Source: Forestry Commission Wilting leaves from early summer onwards Fruiting bodies on rachis of decaying leaves

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 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 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 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 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 Lesions due to Hymenoscyphus fraxineus on the stem of pole-stage ash Where there are high spore densities it is possible to see basal lesions associated with direct infection of the stem. Photo: J. Clark 2014

40 Other things we need to be aware of with Ash trees Ash tress by the River Eamont, Cumbria Tree 1 Tree 2 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.. Photo: E. R. Wilson 2013

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 Dasineura fraxini the ash midrib gall midge Photo: E. R. Wilson 2013

43 The ash bud moth Prays fraxinella, is a native micromoth. Photograph courtesy of Nigel Straw, Forest Research Ash key gall caused by the eriophyid mite Aceria fraxinivora. Source: OPAL

44 Nectria canker is caused by the fungus Neonectria galligena. Emerald Ash Borer (Agrilus planipennis) is currently NOT present in UK. Source: OPAL

45 Emerald Ash Borer Most Unwanted! Not present in the UK at present time; risk of future introduction Emerald ash borer on leaf of American white ash, Fraxinus americana. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015

46 Emerald Ash Borer Most Unwanted! Not present in the UK at present time; risk of future introduction Emerald ash borer. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015

47 Emerald ash borer damage to American white ash, Fraxinus americana. Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015

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 Emerald ash borer damage to American white ash, Fraxinus americana. Scarborough neighbourhood, Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015

50 Emerald ash borer damage to American white ash, Fraxinus americana. Scarborough neighbourhood, Toronto, Ontario, Canada. Photo: E. R. Wilson 17 June 2015

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 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 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: Reporting tree health issues:

54 livingashproject.org.uk Project partners:

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 First presented: This version: v3.0,