Sick Series: Is the oozing wound on my horse chestnut infectious or dangerous?

13th May 2019

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Sick Tree Series

Yes. Well, that was the quickest blog I’ve ever written! OK, you’ll probably want to know how worried you should be, so I’ve put together a few morsels of information to help you identify what’s wrong with your horse chestnut and whether you should be calling in the experts to take a look.

What’s wrong with your horse chestnut?
More often than not, the oozing wound you’ve found on your horse chestnut has been caused by a fungus-like pathogen, a bacterial infection that would usually get in through damage caused by poor pruning, a knock or scrape that has weakened the protective layer of bark. This then grows inside the softer inner layers and breaks out into a lesion, a ‘canker’ which bleeds red, yellow-brown or even black thick liquid which then trickles down the tree.

These cankers can be at the base of the tree, further up the trunk or on branches and eventually, due to the internal damage they are causing, leaves begin to die back then not regrow. First branches then the whole crown fails to spring back to life in the springtime.

First noticed in the UK in the 1970s, thirty years later there were still very few cases reported, whether because the disease simply had not taken hold or there were just fewer people able to diagnose the condition. However, just a decade later it was believed that around half of all horse chestnuts in the UK were infected with the disease.

Trees of all ages can get the disease and because it kills the tree through slowly strangling it, smaller, younger trees are more likely to die because of it more quickly. However, even the largest of mature horse chestnuts are susceptible and will eventually die.

Progression within a tree may be slow, but from the spread of the disease across the whole country we know that it’s highly infectious, so if you suspect your horse chestnut has cankers you should call in an expert to take a look.

Tree expert’s survey
The first thing they’ll do is to establish the cause and how dangerous it might be to your surrounding trees. They’ll perform a survey of your garden’s trees to see whether any others are showing signs of infection and may also look for symptoms on neighbour’s trees to see how far it has spread.

We know that no chemicals work on these lesions, so we are left with managing the condition. Are your trees safe or has the illness weakened them? Should infected branches be removed to limit the spread of the disease or should the entire tree be felled? Infected branches or wood should be burned and never chipped and tools used need to be disinfected before used on other trees to prevent spread of this infectious disease.

Essentially, if you notice some liquid oozing from a lesion of dead bark on your horse chestnut, call a tree surgeon or arborist to help you review your options. See it, report it. Call us on 0208 292 8992. We’re always happy to pop round or to help with a little advice or assistance.

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