Further to our earlier post on ash dieback disease, we can now provide more images and information from the University of Vienna on the symptoms of the Chalara fraxinea infection of ash trees.
In addition, again from University of Vienna, we have a video of the release of fungal spores from ash twigs infected with the reproductive stage of C. fraxinea, called Hymenoscyphus pseudoalbidus. It is this trumpet-shaped mushroom stage that we may see develop in the UK in spring 2013, and it is the prevention (or at least limitation) of this stage that needs to remain in sharp focus.
The ash tree dieback story continues, and we have been fortunate to talk with tree experts at the IFFF to understand their views on what the future might hold for the UK's ash tree population.
The prognosis isn't pretty, but then you will have gathered that already from media coverage of ash tree dieback. There are, however, glimmers of hope – and luckily, such glimmers are very much grounded in what has already been seen in other countries. Some ash trees can be naturally resistant to the disease, even of the same species and variety that are succumbing to the infection, as the image below shows:
The UK's task in the coming months and years is twofold: first, to do all we can to sensibly limit the spread of the disease (sensibly being the operative word – a mad rush to deforest ash could remove genetically resistant trees); and second, to ensure that we understand and manage the ongoing genetic diversity of the surviving trees.
On page 2 of this post, we have more images of ash trees that have been infected with the C. fraxinea fungus, which can help you to confirm whether your ash trees are suffering from dieback.
Ash tree dieback disease images
(For more images, please see our earlier blog post on ash dieback disease)
This section presents a gallery of the Chalara fraxinea fungus and trees infected by it. Images include microscopic images of the pathogen, lab-grown fungal cultures, branch and stem lesions, leaf wilt, and crown dieback.
Click the pictures to view full size...
Fig 1: The pathogen Chalara fraxinea under a microscope
Fig 2: Diseased leaves, twigs and branches eventually fall to the floor, setting the scene for the reproductive stage of the fungus – a trumpet-shaped mushroom called Hymenoscyphus Pseudoalbidus
Fig 3: Cultures of the Chalara fraxinea fungus, grown for research purposes at the IFFF in Vienna.
Fig 4: A tell-tale sign of ash dieback disease is a necrotic lesion (tissue death) on stems, twigs and branches
Fig 5: Once the fungal infection spreads fully across a stem or branch, nutrition is cut off beyond that point and leaves begin to wilt and die.
Fig 6: Continued leaf loss works back towards the trunk of the ash tree, giving the disease its common name of Ash Tree Dieback.
Fig 7: Cross-sections of dead wood show how far into the trunk necrotic lesions can reach
The fungus in the UK would reach its reproductive (sexual) stage around spring 2013. Official advice is not to disturb ash leaves and debris. We think that it may be better to rake them up in winter and burn them before the spores are released as temperatures rise.
We would very much welcome your thoughts and comments on ash dieback disease – please feel free to leave them below.