Anyway to dodge elm disease?

[se7enthdevil]

it's the big tree on the corner

 

pan left.

 

https://www.google.co.uk/maps/@51.528124,-0.6591082,3a,90y,315.84h,83.9t/data=!3m4!1e1!3m2!1sSRSFLfvyok-O-B_mwUypfg!2e0!6m1!1e1

[Agi-Smash]

Thats more like it, thats what i want to grow, a blimmin great big one. How old will a elm live if it stays structurally sound

[Chris at eden]

Princeton elm is supposedly resistant. Ulmus Americana Princeton.

[se7enthdevil]

couple of hundred years i think...

 

if anyone can tell me exactly what species this is i would be gratefull.

 

as i said i guessed u. laevis but am probably wrong.

 

it's about 40' high and there is plenty of DED in the park as the hedges are full of dead examples of the species with dark green leaves made of sandpaper. this particular elm has softer leaves and is a paler green.

[Agi-Smash]

How big a job would it be to "borrow" a bit of a healthy tree and propagate another one from it?

[agg221]

OK, borrowed my wife's computer.

 

Several things have come up in the meantime, which I'll try to address in no particular order.

 

English Elm, and other suckering types, don't coppice very well, Wych Elm does.

 

Yes, you can prolong the life of a tree if you prune out infected branches. The tree shuts down progressively as the fungus spreads, so you can stop it by cutting ahead.

 

Propagating from a healthy tree is only any good if the tree is resistant. There are lots of healthy trees, very few resistant ones (unless they are large, in which case they might be - see below).

 

Princeton elm is resistant to the American strain of DED, not the European one, as has been rather embarrassingly demonstrated in the avenue planted by Prince Charles at Highgrove.

 

U.laevis is not resistant - it's just that the beetles don't like it (see below).

 

Some of the Asian species are resistant, as are some of the hybrids, particularly Sapporo Autumn Gold, which is fully field resistant, but takes some care to grow a good habit. It is worth planting, although it doesn't end up looking like the classic 'English Elm).

 

Elms will live up to 800yrs, although normally not much more than 300 or so.

 

I'll cover resistance in another post.

 

Alec

[se7enthdevil]

are you able to tell which my local tree is then alec?

[agg221]

OK, resistance.

 

First question, what is resistance?

This initially seems obvious - the tree doesn't die of DED. In practice, it isn't, as it depends on why the tree doesn't die.

 

True resistance is when a tree which is infected with DED doesn't die. It may do several things instead. At best, nothing happens, alternatively there may be some wilting from which the tree recovers, or the infected shoot dies back a bit, or a whole branch dies, or the tree dies. This forms a continuous scale of resistance, of which the first three are probably tolerable. There is also a question of dosage. In resistance trials, young trees are infected with a massive dose of DED, many times what they would ever get in the field, so practical field resistance may be much greater.

 

The alternative to resistance is that the beetles are not attracted to the tree. When DED first hit, it was initially thought that Wych Elm (U.glabra) was resistant as the trees didn't die, but it turned out that the trees were just less attractive to the beetles, so they ate the English Elm until it died and then turned their attention to the Wych Elm, which proved equally unresistant. U.laevis is an extreme of this, in that it is so unattractive to beetles that they leave it alone, even though it dies rapidly if deliberately infected in inoculation trials.

 

Another factor is shape. Beetles like upward facing, young, vigorous shoots. They don't like short, stubby shoots on old trees and they don't like weeping branches as the point where the stalk joins the branch, where they feed, is at the wrong angle. This means that old, slow growing, weeping trees get left alone. However, if you propagate from these trees, the young, vigorous form is now attractive to the beetle, gets attacked and dies.

 

So what can be done about it?

There have been breeding programmes running for decades, mainly in The Netherlands, France, Italy and Spain. These started by crossing U.minor with various Asian species with inherent genetic resistance. Several generations later of crossing produced some trees which retained genetic resistance and bred back in the European characteristics. Probably the best of these come from the Italian programme, the most promising being the variety Morfeo. This was briefly released in the UK, before concerns over resistance to phytoplasma (Elm Yellows). The Dutch/French programme has produced a few rather less resistant, but still useful varieties, which may or may not survive in field plantings.

 

The Spanish took a different approach and screened over 10,000 native trees, identifying seven with inherent genetic resistance. These are interesting as they are true U.minor with resistance. You can find details (and pictures) here:

 

http://www.sisef.it/iforest/pdf/?id=ifor1224-008

 

Note, this was only published this August, immediately after the varieties were patented. This is very encouraging as patenting is the precursor to commercial release, which will hopefully come in the next few years.

 

Meanwhile, I'm trying to get things together to repeat the Spanish programme here in the UK, as there are some promising elm clones here, which have not been tested. One of the most interesting is in my current avatar.

 

Alec

Edited September 15, 2014 by agg221

[agg221]

are you able to tell which my local tree is then alec?

 

It is the tree I spotted on my way home from yours, but I took such a random route I couldn't find it again!

 

Can't tell what it is from the form, although it could be Sapporo Autumn Gold. Some close-up pictures of leaves would help, or I'll have another look next time I'm passing.

 

Alec

[Wolfie]

Very interesting Alec,

There's a couple of big ones left in the Cambridge Colleges, Girton College still has one or two biggies, Corpus Christi has a very large one (guess 80ft-ish) and DED is rife there - all of their smaller Elms have died off. Been meaning to take some cuttings.

 

Ed

 

 

 

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