The bleeding cankers and dying trees
Stem bleeding on Horse Chestnut in the UK was first reported in the 1970s, when the cause was found to be a fungal pathogen known as Phytophthora (Brasier and Strouts,1976). The same disorder had also been recognised in the USA much earlier in the 1930s (Caroselli, 1953).
Incidence of the disease
Until recently, such Phytophthora bleeding cankers were only seen in the south of England (Strouts and Winter, 2000). However, over the past four or five years, the number of reports of Horse Chestnut trees (Aesculus hippocastanum) with ‘bleeding cankers’ has increased markedly.
Symptoms visible on affected trees include bleeding areas on their stems and sometimes on their scaffold branches. The increased incidence of stem bleeding on Horse Chestnut is not just limited to the UK; the Netherlands, France and Germany are also experiencing a similar upsurge.
Closer investigation of the bleeding cankers on Horse Chestnut has revealed that Phytophthora is no longer the primary causal agent. Instead there is accumulating evidence that a different pathogen is responsible for the increase in these symptoms on Horse Chestnut.
In 2003 the Disease Diagnostic Advisory Service (DDAS) of Forest Research received more than 60 reports of stem bleeding in Horse Chestnut, while in 2004 a further 90 reports were received. So far 70 reports have been collated for 2005. Affected trees have been recorded as far north as Lancashire and Glasgow.
What trees are affected?
Trees of all ages have been affected by the recent disease upsurge. Young trees with a stem diameter of only 10cm (4 inches) have been found with advanced symptoms. However, the impact on the environment can be particularly profound when large, mature trees are infected and disfigured by the disease. If the disease is severe and the areas of bark which are killed are extensive, large trees can undoubtedly be killed. However, younger trees (10- 30 years old) are at greater risk and can succumb to the disease in just a few years (3-5) as the smaller diameter of their trunks means that they can be girdled more quickly.
- Extent of the problem
- Reasons for increased incidence?
- Symptoms and casual agent
- Diseases with similar symptoms
- Advice on disease management
- About Horse Chestnuts
- Other common pest and disease problems of Horse Chestnut
- Photo gallery
Horse chestnut leaf miner
This is now firmly established throughout the country. It is continuing to spread and wherever it becomes established, numbers quickly build up and cause extensive damage to the foliage. While it is very disfiguring and the cause of premature leaf fall, C.ohridella is not known to kill otherwise healthy trees. The Forestry Commission are not advising the removal of trees on the grounds that they are infested with this pest, although they do not yet know what the long-term effect on tree health will be following repeated defoliation, year after year. There are no recommended methods for management of the pest on the tree itself. Chemical insecticides are difficult to apply safely and efficiently to large trees. They are also expensive and pose environmental hazards. A much safer and more practical means of control is to remove and destroy fallen leaves during the autumn and early winter. Collected leaves should either be burned or composted thoroughly to destroy the over-wintering pupae residing inside.
For further information contact:
Dr Joan Webber, Forest Research, Alice Holt Lodge,
Farnham, Surrey GU10 4LH
Tel: +44 (0) 1420 22255, Fax: +44 (0) 1420 23653,
Email: firstname.lastname@example.org or the Tree
Disease Diagnostic and Advisory Service.
How to use this difficult timber
by Richard Chapman
"Fell it quick - dry it - work it quick"
As a woodturner producing pieces mainly for the decorative art market, I look for different qualities in timber compared to other users. Thus, Spalted Beech, crotch figure, burrs, holes and cracks loom large in my requirements, to catch the eye of art gallery loiterers. My working practice is to chainsaw billets as big as possible. Then rough turn them, leaving sufficient thickness to turn out distortion when dry. Thereby, a 20 inch cube will result in a finished work in 6 weeks. Otherwise wet timber can be turned very thin and finished wet in one session, resulting in an asymmetrical object, after the usual distortion has taken place whilst drying.
Horse Chestnut has very positive as well as negative features.
- As there is little or no commercial market for it, firewood merchants and tree surgeons supply at minimal cost.
- It cuts easily with a chainsaw, and on the lathe, cuts crisply and quickly. Being soft, hollowing big vessels through a small hole is relatively speedy.
- Drying is remarkably quick. Rough turned pieces can be stood out in the sun or placed on shelves over a heat source without cracking. My favourite method is to hang a 40 watt light bulb inside the vessel for several days. Little distortion takes place as drying is from the inside. The creamy white colour is preserved and large vessels are completed in as little as 15 days.
- Burrs and figured timber can be striking in appearance (think Ripple Sycamore x 3) and when dyed and sanded back, even more so. Care must be taken, though, that all finishing marks are removed as the dye will highlight these as much as it does the figure.
- Felled timber noticeably begins to deteriorate within days. It must be converted and stored under cover a.s.a.p. Blocks cut in November and left exposed to the elements were stained four inches into end grain and two inches into side grain by the first week in February !
- The timber is very soft but does not splinter. It can be marked easily with a thumbnail. Therefore I seldom make bowls from it as they are more likely to receive casual damage. Objects which stand on display, for their decorative effect, are a much more realistic use for this timber.
- Summer-felled blocks are very open to fungal attack. Stacked with large air spaces between, all of one batch (a ton +) was infested, through the core, within three weeks. Extra value for me though !
I would suggest that, as well as use by specialised turners, this timber would make excellent veneers.