What’s happening to our conker trees? The dying out of the horsechestnuts..

Has anyone noticed that all our conker trees are dying?  They are brown and crispy and aren’t producing the fat juicy conkers they used to when we were children.  A blight on the scale of Dutch Elm disease (responsible for annihilating the elm population of the UK in the 70s), has been devastating our horsechestnuts over the last few years.   And no-one seems to have a cure for it.   Will our future generations have to go without conkers and not benefit from the beauty of these majestic trees?

What’s happening is the trees are under threat from a lethal combination of pests, diseases and unfavourable climatic conditions attacking them simultaneously.  The leaf miner moth (Cameraria ohridella) and the fungus (Guignardia aesculi).  Not to mention the effects of drought.  And now there is another, greater threat to these stately trees – namely Bleeding Canker.

The first symptom is often an area of bark where a yellow / brown / red liquid seeps out. In the spring, this coloured fluid is usually transparent but in warmer weather it may become cloudy. When it is dry and hot, the flow may dry up – leaving a dark crust on the bark. However, the bleeding may start up again in the autumn. These observations have lead to the suggestion that the pathogen is most active when conditions are mild and moist (i.e. in spring and autumn).

Where the pathogen has been active, bark, cambial tissue and the phloem (the sugar conducting tissue) are destroyed. If this damage spreads around the trunk then more general effects will be seen, namely yellowing of the leaves, early leaf fall, failure to set fruit (no conkers!) and damage to the crown of the tree; branches may be weakened and fall.

Dr Jean Webber, the Principal Pathologist at Forest Research, the scientific arm of the Forestry Commission, said that bleeding canker has been spreading quickly across Britain since 2001, having been confined to the south of England since the 1960s.

She said Forest Research believes its increased prevalence has been caused by a newly detected Indian-born bacterium, Pseudomonas syringae pv aesculi, replacing Phytophthora, a plant-destroying fungus, as its main cause. This may have been aided by mild winters and wet springs in recent years.

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Dr Webber said: “There’s nothing much you can do about it if your tree displays the symptoms. Our advice is: if you can do, leave the trees well alone, unless they become so damaged that they create a safety hazard.  “Disturbing the trees, by pruning them or making other attempts to clear the infection, may result in the bacteria being spread even further.”

It’s both sad and surprising how little publicity there has been about the plight of the horse chestnuts.  I hope something can be done so future generations get to enjoy these majestic trees and their beautiful conkers.  Once you become aware of it – you’ll be surprised at how many horse chestnuts there are in the UK – most British villages and parks would have a significantly different  look and feel if we imagine a world without them.

    • VP
    • August 15th, 2010

    There are some potential cures for both leaf miner moth and bleeding canker being researched at the moment.

    I reported on them last year on my blog and they look promising.


    • Thanks guys. Great to hear your interest. And VP – delighted that there are potential cures being researched. Do you know if much progress has been made recently?

    • dorsetmichael
    • August 15th, 2010

    yes there is a tragedy unfolding here…a neighbour has an eighty year old chestnut tree with the first signs of the bleeding canker but we are hoping it will be a big enough tree to survive…it is important to note that one should wash ones hands clean of any bacteria if touching an infected tree to avoid spreading the disease…good post, lovely photos…

  1. This is such an important issue, thank you for highlighting it Elspeth. Sadly it is not just the horse chestnut species of the genus Aesculus which suffers from the bleeding canker, other species in the genus, such as the beautiful Aesculus indica (Indian horse chestnut), also suffer. I have seen a specimen in the Chelsea Physic Garden with the disease.

    Let us hope a cure can be found before we lose these beautiful trees from our parks, churchyards, countryside. They may not be native, but they have been with us for over 500 years, and it is hard to imagine our landscapes without them.

  2. Wow, I hadn’t realised it was an actual problem… Last year our Horsechestnuts leaves went yellow very early and looked very much dead. I assumed it was due to the drought we had over September/October as most other trees were struggling and also had dead curled leaves, but the same has happened again this year when all other trees are ok. They must have this infection!

    • VP
    • August 17th, 2010

    I know the wasp research is ongoing and a number of schools in the Bristol area are helping to collect the data. The garlic treatment is available but expensive. However it is cheaper than the cost of replacing the tree.

    Bacterial canker isn’t necessarily a death warrant for the tree, some are proving to be resistant…

  3. Good to hear. Thanks for sharing

  4. Truly heartbreaking.. I am sending up prayers as we speak

  5. Wow.. keep your head up!! Things will get better

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