Dutch elm disease

[Steve Bullman]

Scuse my ignorance, is Dutch elm disease considered a fungal disease?

 

@David Humphries

[benedmonds]

Yes, but it is carried/spread by beetles..

Edited June 8, 2018 by benedmonds

[Steve Bullman]

Thanks 

[Dan Maynard]

Another Dutch elm question which intrigues me is why trees get to a certain age before being infected, somebody said it was when the bark cracks but I always thought it was a certain height as the beetles fly about high up?

[benedmonds]

26 minutes ago, Dan Maynard said:

Another Dutch elm question which intrigues me is why trees get to a certain age before being infected, somebody said it was when the bark cracks but I always thought it was a certain height as the beetles fly about high up?

The wood has to be a certain size for the beetles, IIRC the beetles enter or are attracted to wounds.. I  have pruned (against my advice) two healthy mature elms with no signs of DED and been called back a few years later to fell as they were dead. 

 

https://www.forestry.gov.uk/pdf/RIN252.pdf/$FILE/RIN252.pdf

Edited June 8, 2018 by benedmonds

[Swampster]

Ophiostoma ulmi (fungus) carried by scolytus scolytus (beetle).

[Gary Prentice]

9 hours ago, benedmonds said:

The wood has to be a certain size for the beetles, IIRC the beetles enter or are attracted to wounds.. I  have pruned (against my advice) two healthy mature elms with no signs of DED and been called back a few years later to fell as they were dead. 

 

https://www.forestry.gov.uk/pdf/RIN252.pdf/$FILE/RIN252.pdf

Can't disagree, but I don't think avoiding pruning guarantees that they elms won't get infected at all. I know plenty of non-pruned trees that did finally get infected. 

 

I think that the beetles themselves have/had preferred host species. Some species of elm were originally thought to be safe, that was until the preferred host trees had gone and then the beetle had to make do with what was available, to feed and breed on.

 

10 hours ago, Dan Maynard said:

thought it was a certain height as the beetles fly about high up?

Is it more to do with the size of tree that the beetles breed on. A small tree could provide a feeding habitat, get colonised but compartmentalise the fungus ie. have a few infected branches. A young tree has a good ratio of dynamic energy (sapwood/heartwood) so can cope. More mature trees provide a breeding habitat, much higher beetle numbers, and simply can't cope energy wise and decline and die.

 

I watched the odd, isolated,mature elm for many years with the symptoms of the odd yellowed branch. They've seemed to deal with it, then suddenly over twelves months more or less the whole canopy yellows. I wonder if this is because it's becoming a breeding host and suffers a beetle population explosion when they hatch. 

 

The dynamics of host tree/ beetle population/ climate must be a factor. I image that locally the beetle population must be very small, there's very few larger elms and I can't remember the last time I come across a gallery on a dead elm. Twenty years ago, every dead elm of any size had them.

 

[Gary Prentice]

11 hours ago, Steve Bullman said:

Scuse my ignorance, is Dutch elm disease considered a fungal disease?

 

@David Humphries

It's also a vascular wilt disease, like ash dieback which doesn't have an insect vector/carrier but has airborne spores.

[Dan Maynard]

Is it more to do with the size of tree that the beetles breed on. A small tree could provide a feeding habitat, get colonised but compartmentalise the fungus ie. have a few infected branches. A young tree has a good ratio of dynamic energy (sapwood/heartwood) so can cope. More mature trees provide a breeding habitat, much higher beetle numbers, and simply can't cope energy wise and decline and die.
 
I watched the odd, isolated,mature elm for many years with the symptoms of the odd yellowed branch. They've seemed to deal with it, then suddenly over twelves months more or less the whole canopy yellows. I wonder if this is because it's becoming a breeding host and suffers a beetle population explosion when they hatch. 
 
The dynamics of host tree/ beetle population/ climate must be a factor. I image that locally the beetle population must be very small, there's very few larger elms and I can't remember the last time I come across a gallery on a dead elm. Twenty years ago, every dead elm of any size had them.
 

We have loads of elms both old hedge and suckers that have grown up from where there were big trees in the village 40 years ago, and I see galleries in the tops of every one I cut. So the beetles appear to be doing just fine round us, plenty of habitat.

[Stubby]

How did they keep it out in Brighton ?

Edited June 9, 2018 by Stubby