Elm treatment.

[skyhuck]

We have a dead Elm to remove, interestingly there is a neighbouring Elm thats in rude health. According to the customer it was treated by Myerscough collage to prevent DED. Apparently the dead tree was already to far gone to be treated.

 

Obviously its not that uncommon for some Elms in a group to survive, so it could just be coincidence that this tree lived.

 

Does anyone know anything about the treatment and how successful it was??

[Jake Andrews]

We treat elms hear but that's for Elm leaf beetle, DED hasn't made it into Australian waters yet.

We treat with stem injection every 3 years.

[Tom D]

No but I'm interested?

 

There's one I'm my dads garden that is still going strong, there were two others that went 20+ years ago... Got to be genetics..

[MattyF]

Felled about 13 big elms in a park 6 or so years ago that had been treated in the 80's to great expense, most had died or were dying at the point of felling so my guess is it had worked to a degree but I don't think any one is offering injections or treatment any more also all other elms in the immediate area had long since died so that's my reasoning to it been effective.

Felled quite a few more survivors that to my knowledge had never been treated in the same time period all within a 10 mile radius to these about the same time so it was weird they had survived for so long being left as lone trees to suddenly succumb bearing in mind elm probably accounted for the majority of trees in the area before DED.

I dead wooded this one when I was about 17 and it finally died around 7 years ago shame as it was an amazing tree and I don't think a wych elm that is more resilient and has a few survivors.

Edited May 22, 2015 by MattyF

[agg221]

Treatment is a fungicide. It is effective, but it has to be repeated every year.

 

Elm disease is worst in years when there are a lot of spores and a lot of beetles. It's a bit like a person getting a cold - you inhale cold germs pretty much with every noseful of air but you only get a cold when the conditions they land in are right and there are more incoming germs than your system can quickly kill.

 

Some trees (genetically) can tolerate a higher dosage of fungi before they are affected. Some are less attractive to the beetles. Beetles don't like to live in some conditions.

 

If you happen to treat a tree in a year which favours the spores and the beetles then it is won't be infected. If you then don't treat it in other years but there are fewer spores/beetles around, or the tree happens to be less attractive to the beetles, you may well not see it get infected until the next time there is a bad year.

 

The critical dose is very variable. English Elm virtually seems to die from a single spore-carrying beetle whereas other strains such as Huntingdon Elm (as per MattyF's pictures) takes a higher dose. Some strains/hybrids can tolerate such a high dose that they are effectively immune in the field.

 

Another factor is the health of the tree. Like people, a young, vigorous healthy tree is far more likely to survive than an old, weakly growing tree in poor health.

 

Returning to the original point, the need to treat annually is the reason it has been abandoned for all but a very small handful of trees. I also vaguely recall that the effective fungicide has now been withdrawn for this purpose.

 

Alec

[skyhuck]

This Elm was apparently treated 3 times 6 month between treatment. Its many years since the last treatment, so my guess its just one of the lucky ones thats resistant.

 

I alway put the fact that some are resistant down to cambium thickness.

 

Young trees are not infected, presumably due to cambium thickness, some mature Elms may just have thinner cambium. If the cambium is too thin the beetle cannot burrow.

[agg221]

This Elm was apparently treated 3 times 6 month between treatment. Its many years since the last treatment, so my guess its just one of the lucky ones thats resistant.

 

I alway put the fact that some are resistant down to cambium thickness.

 

Young trees are not infected, presumably due to cambium thickness, some mature Elms may just have thinner cambium. If the cambium is too thin the beetle cannot burrow.

 

The infection is not initially transmitted by the beetles burrowing but by them feeding. They do this at the base of the leaf stalk (leaf/stem crotch). The spores are rubbed off the beetle and enter the wound. As such, pretty much any elm can be infected (there are English Elms under 2' high which have been killed recently). The beetles prefer to fly at about 6m, so as long as they can find food at this height this is usually the limiting factor. It's only when food gets scarce that they come down to the smaller saplings. Beetles prefer to lay eggs on weakened trees which have been infected - these give off chemicals which attract them. This can cause secondary infection.

 

There may be a link between survival and the structure of the wood cells, and also leafing out time of a particular clone. If you are interested, this new paper explains in some detail:

 

Santini A, Faccoli M (2015). Dutch elm disease and elm bark beetles: a century of association. iForest 8: 126-134.

 

Alec

[skyhuck]

The infection is not initially transmitted by the beetles burrowing but by them feeding. They do this at the base of the leaf stalk (leaf/stem crotch). The spores are rubbed off the beetle and enter the wound. As such, pretty much any elm can be infected (there are English Elms under 2' high which have been killed recently). The beetles prefer to fly at about 6m, so as long as they can find food at this height this is usually the limiting factor. It's only when food gets scarce that they come down to the smaller saplings. Beetles prefer to lay eggs on weakened trees which have been infected - these give off chemicals which attract them. This can cause secondary infection.

 

There may be a link between survival and the structure of the wood cells, and also leafing out time of a particular clone. If you are interested, this new paper explains in some detail:

 

Santini A, Faccoli M (2015). Dutch elm disease and elm bark beetles: a century of association. iForest 8: 126-134.

 

Alec

 

Cheers, I"ll take a look at that

[agg221]

Cheers, I"ll take a look at that

 

You're welcome - Fig.1 in the paper is particularly helpful.

 

Also worth noting that they have the feeding location as the twig/stem crotch rather than the leaf/stem crotch - this is very recent work by some very respected experts so I would go with this rather than my originally stated location.

 

Alec

Edited May 24, 2015 by agg221