Pruning large elms

[JimM]

I've got a couple of elm jobs coming up, all removals though. But in two locations there are really healthy looking trees next to full skeletons, all around the 60ft in height.

Just finishing a survey that had two elms on the site. One fully dead and heading towards skeletal, the other is in full leaf to the tips. Both are going to be removed by the council for a minor road to be widened, which is a shame.

Felled some big elm on the Ballindalloch estate for Big J. The ones we took down that were "healthiest" looking had been hammered at the butt by kretz and were majorly hollow, much to our disappointment.

Only pruned one, a large elm in the centre of Elgin. We removed a large limb over the top of asbestos clad garages, plus a couple of limbs away from the house roof. The large limb was fine, rigging in small chunks, cos the stuff is heavy, the smaller stuff did do its damnedest to tear.

[Charles Hey Arborist]

Why are they being pruned?

 

 

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Crown reductions to hopefully stop them failing... Very decayed at the base.

 

Can't find any UK based info, but in the US they don't prune april-July as that's when the beetle is most active, and the open wounds attract the them. Is it safe to assume the European elm bark beetle is active at a similar time of year?

[Charles Hey Arborist]

And what about cleaning/disinfecting chainsaws before each tree or something? Incase I've cut some DED wood and spread it about?

[woodyguy]

Would second the advice about avoiding now. I had to reduce a lovely big wych elm that had stood for many years and assumed it was immune. Had to cut it in mid summer and within a year it was stone dead from DED. So much for immunity!

[agg221]

I have some feedback from the person who runs resistantelms.co.uk - he previously ran the Kentish Elm Conservation Programme which carried out maintenance to preserve surviving trees.

 

Comments were as follows (my comments are in brackets):

 

There is a reasonable chance that surviving trees show some resistance, or are unattractive to beetles - it isn't just luck.

If it's disease resistance then great, they are likely to survive attack anyway, but resistance is not all or nothing - the more beetles that go for a tree at once, the higher the dose of disease and the more chance the tree will die, so the aim is to minimise the attack.

Beetles are active from April to September (the trees also bleed) so prune only when the tree is fully dormant.

The beetles are attracted by the smell of the cut surfaces, so keeping the cuts to a minimum is a good idea. Also, whatever you do, burn, don't chip - the chippings will attract in every beetle for miles around! Similarly, remove any cut timber from site, otherwise the beetles which hatch out will just fly back up into the tree (I suppose you could chip, be scrupulously careful about removing every bit of chipping from site and make sure they are buried in the chip pile by the time spring comes around).

The beetles also prefer vigorous young growth. This means that when pruning it is best to discourage epicormic growth from breaking, so a crown thin and gently phased work would be better than going in hard.

There is some thought that beetles don't like short trees (if this is the case then a full on re-pollard may not be a bad thing).

 

Charlie - interesting information on the single tree. There is a surviving large elm at Acton's Farm, Sawbridgeworth, which shows the same weeping habit. It is reckoned to be Ulmus x hollandica, but there is a lot of genetic diversity in this type and it is possible that they are either directly related or coincidentally resistant.

 

Alec

[Paul Cleaver]

And what about cleaning/disinfecting chainsaws before each tree or something? Incase I've cut some DED wood and spread it about?

 

that sounds a good idea use bleach or if anyone can comment on anything

more up to date

[Chris at eden]

Less leaves to attract the bugs and the tree tree can put more oomph so to speak into fewer branches.

Most of the elms that are still alive up our way are pollards or high fells.

This is just my take on it.

 

 

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Think you may be onto something with the height reduction bit as whenever you see elm regen on the road side it seems to be fine up to a certain height then gets done. Not convinced by the oomph bit though. Trees use two types of energy, potential and kinetic. Potential is that stored within the wood in the form of carbs. Kinetic is energy in motion being used for growth, defence, etc which is created by photosynthesis or the oxidation of potential energy. The removal of branches would remove potential energy and reduce the rate of photosynthesis due to less leaves. There would also be an increase in demand for energy as the tree would need to compartmentalise all of the cut surfaces. The combination of these three factors would mean less surplus oomph in my view.

[Gary Prentice]

Think you may be onto something with the height reduction bit as whenever you see elm regen on the road side it seems to be fine up to a certain height then gets done. Not convinced by the oomph bit though. Trees use two types of energy, potential and kinetic. Potential is that stored within the wood in the form of carbs. Kinetic is energy in motion being used for growth, defence, etc which is created by photosynthesis or the oxidation of potential energy. The removal of branches would remove potential energy and reduce the rate of photosynthesis due to less leaves. There would also be an increase in demand for energy as the tree would need to compartmentalise all of the cut surfaces. The combination of these three factors would mean less surplus oomph in my view.

 

I'd agree and, but IMO regrowth isn't touched until a certain size due to the feeding habits of the beetle. Early symptoms of DED is usually fairly high in the canopy.

[MrHairy]

I was told the beetles usually fly around 10 metres up, so any elm less than 10m has a better chance.

 

Can anyone confirm this?

[Rich Rule]

When deadwooding large Elms in Norway, during the leafy period we have to be so careful not to cut I to live wood or to damage epi growth. As this attracts the beetle.