1. Ash Dieback Chalara fraxinea
Alistair McCracken & Louise Cooke
Applied Plant Science & Biometrics Division
November 2012
Note: Do not change background, font or font colours.

2. Ash (Fraxinus excelsior)

3. Chalara dieback of ash Chalara fraxinea (asexual)
Anamorph of new species called: Hymenoscyphus pseudoalbidus (sexual)

4. Ash Dieback
The causal agent of dieback of European ash (Fraxinus excelsior) was first (2006) described as Chalara fraxinea.
Study of the teleomorph of C. fraxinea revealed a species complex but that the strain causing ash dieback should be re-assigned to Hymenoscyphus pseudoalbidus (2011).

5. Chalara fraxinea hosts
Fraxinus excelsior (European Ash)
F. angustifolia (Narrow-leaved Ash)
F. nigra (Black Ash)
F. ornus (Manna Ash / South European Flowering Ash)
F. pennsylvanica (Green Ash)
F. americana (White Ash / American Ash)
F. mandschurica (Manchurian Ash)

7. Impact
“The disease is particularly prevalent in Denmark where up to 90 per cent of trees in many locations are infected and all are expected to die. Chalara ash dieback has the capacity to inflict on common ash what Dutch elm disease did to English elm in the 1970s. That is to essentially wipe out the species as forest, woodland, amenity and landscape tree in the UK.”
(British and International Greenkeepers Association Ltd. Sept. 2012)

8. Pathways
Movement of soil, plants for planting or wood are possible pathways for long-distance transmission
Wind-borne spores can move up to 30 km/year
Plants for planting from known infected areas are considered to be the likely means of entry

9. Spread from plant to plant
Aerial spread
Asexual spores are not thought to be an important means of dissemination

10. Sexual spores
Sexually formed spores (Hymenoscyphus psaudoalbidus) can be dispersed by wind and would appear to be the more important means of dispersal

11. Dispersal rate
Evidence from Norway has suggested a potential dispersal rate of km/year.
There is evidence of insect (flies; sap-feeders) dispersing other Chalara spp.

12. Symptoms
Symptoms of Chalara fraxinea can be visible on leaves, shoots and branches of infected trees
In severe cases the entire crown shows leaf loss and dieback

15. intensive dieback of ash ( Chalara fraxinea ) on European ash (
Fraxinus excelsior )
Andrej Kunca, National Forest Centre - Slovakia, Bugwood.org

16. intensive dieback of ash ( Chalara fraxinea ) on European ash (
Fraxinus excelsior )
Andrej Kunca, National Forest Centre - Slovakia, Bugwood.org

17. intensive dieback of ash ( Chalara fraxinea ) on European ash (
Fraxinus excelsior )
Replace with photos recently taken by AFBI from samples.

18. intensive dieback of ash ( Chalara fraxinea ) on European ash (
Fraxinus excelsior )
Replace with photos recently taken by AFBI from samples.

19. intensive dieback of ash (
Chalara fraxinea
) on European ash (
Fraxinus excelsior )

20. intensive dieback of ash (
Chalara fraxinea
) on European ash (
Fraxinus excelsior )

21. intensive dieback of ash (
Chalara fraxinea
) on European ash (
Fraxinus excelsior )

22. intensive dieback of ash (
Chalara fraxinea
) on European ash (
Fraxinus excelsior )

23. Canker caused by Chalara fraxinea on Fraxinus
Prof. H. Solheim, Norwegian Forest and Landscape Institute, Aas, Norway

28. Times of year when symptoms are most likely to be observed
Jan
Feb
Mar
Apr
May
Jun
Jul
Aug
Sep
Oct
Nov
Dec
Leaf
necrosis
Shoot
lesions
Stem
Fruiting
bodies

29. Detection and Diagnosis
Culturing
Difficult to culture
Very slow growing – could take 5 – 8 weeks to get a colony

30. Molecular (PCR)
Molecular lab is fully set up to examine plant samples and / or cultures

31. Thank you