Okay guys, time to get serious…
Let’s talk about the thugs of the forest, tree diseases.
As tree care workers, we should know exactly what’s going on
with the health of our trees, and unfortunately with climate change creating
the perfect breeding ground for these horrid pests, it’s not looking great.
With an already extensive list of diseases out there, the
number is rising and the threat to our trees is becoming severe. This means one
thing and one thing only: we must educate ourselves to the threat, and learn
how to best protect our tree species.
Here are just a few of our current culprits: Bleeding Canker
of Horse Chestnut; Dothistroma Needle Blight; Great Spruce Bark Beetle; Oak
Pinhole Borer; Horse Chestnut Leaf Miner…these may sound like something out of
Lord of the Rings, but they’re far from fictional. All of these diseases cause
a variety of damage to their victims, from limb loss to death.
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| Bleeding Canker of Horse Chestnut - not a pretty sight |
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| Oak Pinhole Borer - pesky little mites! |
And we’re not talking just a few fatalities here and there,
we’re talking tree massacres.
But there’s a new kid on the block, and it’s quickly
becoming the bully of the forest: Sweet Chestnut Blight.
Chestnut Blight is a plant disease caused by the ascomycete
fungus, Cryphonectria parasitica (easy for you to say). In layman’s terms, it’s
nasty…reeeeal nasty. Having already paid a visit to the USA, it has proved
capable of killing billions of trees.
And for those of you who are more swayed by threats to the
economy, remember what these beautiful trees produce: nuts. If Britain sees the
same destruction to sweet chestnuts as the USA, then there will no doubt be a
significant impact to the British economy.
So, where has this nasty piece of work turned up? It was
identified in November 2011 as the cause of dieback in European sweet chestnut
in Warwickshire. It was later found in Sussex. It seems the South of England,
then, is extremely vulnerable, and the thought of our beautiful New Forest
becoming the next target is terrifying.
As with most tree diseases, Sweet Chestnut Blight is spread
locally through wind and rain, as well as through the ever-busy activity of our
lovely insects and birds. And scarily enough, it has also been reported that
the disease can live and feed on dead organic matter, which means is can
survive even once the infected chestnut trees have been removed.
So that you know when you see it, here’s a list of the
symptoms of Sweet Chestnut Blight:
·
All symptoms occur above the ground
·
The bark is attacked, and the disease enters
through fissures or wounds
·
On grafted trees, infections are usually found
in the region of the graft
·
In coppices or orchards, infections are usually
found at the base of the stem
·
Stems or branches become girdled and the dead
bark becomes visible as a sunken canker
·
Above the girdling canker, leaves wilt and turn
brown, but remain hanging on the tree
·
Below the canker, branches have healthy foliage
and, after a short time, new shoots are produced
·
On young branches the cankered bark can be a
bright brown
·
On older branches, the discoloration of the
infected bark is less obvious
·
When the bark is killed quickly the stem is
girdled without any callus formation
·
The disease’s progress can be slower, causing new
layers of bark form under the affected area to grow, resulting in swelling and
subsequent cracking of the outer bark
·
Masses of yellow-orange pustules develop on
infected bark, which erupt through lenticels and ooze long, orange-yellow
tendrils of spores in moist weather
·
Crown dieback
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| A sunken and swollen canker on an American Chestnut |
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| A young American Chestnut with the blight |
So, you need a plan of action for if and when you spot this
beastly bully…
First thing’s first: grab your camera and take some photographs
of the whole tree, and then some close-ups of the symptoms. Then, make sure you
write down exactly where the tree is situated (this is where your iphone’s GPS
comes in handy). You can then email this information to The Forestry Commission
Plant Health Service…
Tel: 0131 314 6414
That’s all for now, fellow tree warriors. Keep a look out
for this new blight, and if you do find any of the symptoms then ping an email
over to The Forestry Commission. And if you could copy us in, too, we’d
appreciate it!
