Save the conker

It's getting rather alarming, cycling round my part of northwest London. At this point in the year only one kind of tree has orange leaves - the horse chestnut.

This is not because the tree is uniquely sensitive to early autumn. It's because every tree near me - and apparently all over London, and far beyond - has been attacked by tiny moths.

These cause the conkers to fall early, and rather too small to be satisfactory for the traditional playground game.

At the same time, vast numbers of horse chestnuts have been attacked by bleeding canker. The Forestry Commission carried out a widespread investigation earlier this year to assess the extent of the cankers' spread. It found symptoms of bleeding cankers in half the trees it surveyed. The chances of trees surviving both attacks at once are small.

Could we be about to see something as bad as Dutch elm disease, which wiped out millions of UK elm trees from the late 1960s onwards? Or could that episode teach us any lessons?

Since Dutch Elm Disease hit Britain in the 1970s, the trees are now restricted on the south coast to a stronghold in the city of Brighton, where officers managed to keep 15,000 elm cultivars and varieties alive. Just tell me what to do, and I'll keep my local conker cultivars alive too.

Comments

[Brien Comerford]

Trees are the lungs of the earth. They provide habitat for wildlife and they are vital in curtailing global warming and pollution. It's sad to read about the demise of any tree or creature.

[roger]

West Sussex chestnuts look sick, also Sycamores are mysteriously losing foliage on the odd branch. Something not quite right.

[john]

There is an apparantly healthy elm tree alongside the road in the parish of Hatcheston in East Suffolk for all to see. And another not so far away in Parham.

[Dom M]

There are horse chestnut trees along my road and these small moths first appeared three summers ago. The wetter summers seem to have stopped them flying around quite so much but the leaves have been brown for weeks and the conkers aren't what they used to be.

This advice to sweep up the leaves and compost them is the first piece of useful advice I've seen on how to help. I hope they find a solution sooner rather than later.

[Mike]

How long before some fruitcake blames it all on global warming?

[Sara]

The same in York too. There are some that appear to be alright but I went out at the weekend to a wood close to where I live and, apart from there being only 2 Horse Chesnut trees that I could find, they were both looking rather ill. Lots of the other trees had brown spots on the leaves too which didn't look healthy..?!

[Bill Peter]

I thought that conkers had been effectively banned by "'elf and safety".

[David Barker]

It is true that horse chestnuts are amongst the first trees to loose their leaves each year. However, this year in my area of southern England - near Salisbury - there have been many horse chestnut trees with withered brown leaves since early summer. Yet interspersed between them and in other places there are plenty of horse chestnut trees in apparent good condition with normal green leaves. We should identify and propagate these HCLM- and presumably canker-resistant varieties and have them ready to plant and replace the diseased trees once they die - as surely they will.

[Sara]

The brown leaves on horse chestnuts (Aesculus hippocastanum and many other species) in the UK is likely to be due to one of 2 cause - the first is a disease, leaf blotch or Guignardia. The second and seemingly more prevalent one is the Horse Chestnut Leafminer, Cameraria ohridella, which is a small moth. This pest is causing early leaf drop on Aesculus across Europe. I was in Germany and Switzerland recently and they have the same problem there too.

A bleeding canker (usually attributed to a specific strain of Pseudomonas) is often associated with the presence of HCLM - possibly as the tree is very stressed by early leaf loss. The cankers can reach the point where the tree is girdled and killed.

One way to reduce the level of infestation of HCLM is to remove affected foliage from the ground and compost it, having covered the leaves with a thick (10cm) layer of soil or compost to stop adult moths emerging and flying off to lay more eggs. Work is still being done to determine whether there are any suitable treatments for the bleeding canker.

Linda is right that Horsechestnuts can sometimes flower themselves to death - though usually this is a stress response, which we see sometimes in the public parks and gardens of London.

If we work to minimise the stress to our trees - keeping the ground under them from being too compacted, ensuring no one digs and disturbs the roots, etc - then they will be more resilient to pests and diseases. We need our trees and they need us, as a society and as individuals, to value them and care more for them.

[Linda W]

Horse Chestnuts/Buckeyes -- the early falling is not a 'bug', it's a "feature"!...
Seriously -- from my readings, they said one of the reasons it's slightly less favourable as a shade tree is that it has a tendency to look dried out and have leaves fall among the earliest of the trees.
Personally, I wonder if it is related to the amount of time and energy the tree spends in the flowering state in the spring to early summer.

They seem to flower with 20-30 cm racimes that last a *long* time -- over a month. I don't think most trees have such long lasting, large flowers.

I hope this double canker problem doesn't spread -- but an early fall isn't necessarily a sign of a significant problem with these trees -- what will count is how well it flowers in the spring -- but I think the higher resource expenditure in flowering may lead to a shorter 'summer' period for this species, but that's just a guess -- nevertheless, because of their attractiveness, they use humans quite well to help them spread. I'm in CA, and I've got one red-dwarf chestnut that's looking like it may thrive -- and another 'regular' (yellow colored racimes) 'Ohio' Buckeye I'm trying to nurture from a bare-root state (poor showing this summer, but it may be enough to help it survive through to next spring. But both are entirely non-native to this area. They make for beautiful nuts that, apparently have some medicinal uses as well -- darn shame that the nuts aren't more edible.

But their intense flowering period and furniture-polished looking nuts tend to make them attractive neighbors ...despite their poor end-of-summer display. I'm always trying to grow things that are not "ideal" for my climate -- but my eyes see more green than I have space and climate to easily support. May have to tear down the house and just build a large glass-house in its place... Don't need no "stinkin'" walls, anyway! (just gotta remember to stop throwing rocks...) :-)

[Simon]

I live in Northern France and I have notice that every year it is the horsechestnut trees that are the first to grow brown every year, starting in around August.
Move along now, nothing to see here.

[Diana]

Apparently some people see the leaves turn brown and fall in late summer, assume their tree is dead and get it felled. The Forestry Commision say DON'T, it is not dead.

[J.Taylor]

At last, some information on this! The trees in New Jersey are suffering too--so I'm afraid that this is already also a US problem.

[Neil Wells]

The writer who talked abought buckeye tree was incorrct in his thinking
that the Horse Chestnut
and the buckeye are the same the chestnut is an edible nut where as the buckeye is not they look
very much a like but are
not the same tree.
I also wish to keep it on that side of the pond and
great success on findind
cure.

[Freemon Sandlewould]

Why do you call it "the conker" ? We had them in Ohio, USA also!

[Joan]

I live in north west London and about mid-June I noticed the leaves of the horse chestnut trees looking rather scorched and thought it had something to do with the environment. I kept mentioning it to friends but they were not interested.

What can we do to keep them alive?

[AMY IN OHIO]

Oh my gosh! Here in Ohio, horse chestnuts are known as "Buckeyes" and share the name with our beloved university's sports teams -- The Ohio State University Buckeyes! When I visited Italy a few years ago I was amazed to find such a proliferation of the ... conkers..! But, when I lived in London for several months I must have missed the conker season. Please find a solution and don't let the dreaded disease and blight spread to this side of the pond!

[Marta]

Same happens in Warsaw... Shame, when I was little, conkers made me look forward to the autumn. Just think of it, such a gloomy weather and no conkers to cheer you up:(

[janet ott]

I noticed while in Père Lachaise Cemetery Paris in August that the chestnut trees were looking decidedly russet coloured. The same phenomenon as in Ealing in London earlier in the month. It's very worrying.

[Bel]

I love conkers, and now that my son has grown up I'm still tempted to pick up the biggest, shiniest ones when no-one is looking! But -- sorry -- isn't the above pic of a sweet chestnut, rather than a conker?

[Sarah]

I live near Bordeaux and all the horse chestnuts around here are going brown. We burn the leaves each year to try and break the moth breeding cycle and hope that the flocks of blue tits feasting on the larvae will do some good too. It is so sad to see our beautiful big tree which provided welcome shade all summer (hmm... what summer?) fading fast.

[Kate]

I live south of Lyon and all the horse chestnuts in the area are brown. The one in my garden has been turning brown in August for the last two years.

[Soreofhing]

The horsechestnuts in Paris all looked beautiful this July.

[B]

Flying into Geneva recently I could see brown trees dotted everywhere, highlighted against all the greenery. Isn't there a Horse chestnut tree vaccine or something?

[Danny]

Was in the Hague in Holland, last week, every Horse chestnut tree, that I saw was brown.