Diagnosis & response to Dutch Elm Disease

[MycoMan]

I have several (presumably root-grafted) elms within a hundred foot diameter, a few of which are showing concerning signs (e.g., leaves flagging in summer, branches apparently dying off).



Someone who I think knows trees suggested it's DED based on markings in this image at 4-5 o'clock, 7-8 and 10-11 o'clock:



Is it? (Sorry about the quality of the shot: I think some of the brown patches in the middle are "skid marks" from the saw.)

I’m not sure how to discern the cambium from other layers, but here are a few more cross-sections from branches:





If it is DED, should I remove infected branches, perhaps cutting the trunk down to below whatever staining is visible? Or should I remove the tree and attempt to pull up the roots, as they're a vector to nearby elms?

Another possibility maybe worth mentioning: I've seen Armillaria mushrooms fruiting not 200' from this location. I don't know that they could cause this pathology, but they might exacerbate it.

Thanks for any help!
Brendan

 

[Raintree]

Classic DED flagging, trees are too small to prune out the infection. The flagging elms are removals. Mature trees if caught early you can prune out the flagging leader, with high volume fungicide injection into the root flare there is a chance to save. All elms in the vicinity are now at risk.

 

[MycoMan]

Classic DED flagging, trees are too small to prune out the infection. The flagging elms are removals. Mature trees if caught early you can prune out the flagging leader, with high volume fungicide injection into the root flare there is a chance to save. All elms in the vicinity are now at risk.

Thanks so much for this assessment, @Raintree. I hope in vain for a more favorable diagnosis, but don't believe I'll find a more accurate one.

Should I cut, debark, and bury this tree, even attempting to pull up the roots (or at least sever them from grafts)? Or would any or all of that be quixotic and futile?

And, to aid my identification of DED in other trees, is the brown running through the center of this young branch (of the tree under discussion here) also a sign?



Thanks!

 

[Raintree]

View attachment img_4164.jpghttps://ag.umass.edu/landscape/fact-sheets/dutch-elm-disease

A picture from above informative site shows what to look for. Sanitation is very important to help slow the spread of DED.

 

[MycoMan]

Great reference. Thanks again, @Raintree.

 

[MycoMan]

Now that I have cut the tree @Raintree helped diagnose as infected with Dutch Elm Disease (DED), I have two questions:

1. Do the pictures in this and the following post suggest I’ve cut the trunk below the DED infection, and can therefore safely leave the stump to re-sprout? Or do I need to remove as much of the root system as possible (because despite the lack of staining, the fungus has spread through the vascular system and will attack nearby root-grafted elms)?
2. Would an expert be willing to point to one or more specific images here, and articulate which (if any) show the tell-tale staining or other unique symptoms of DED? Then I (and hopefully others) will be better able to diagnose DED on our own. (Although I have seen the images on the referenced sites showing the tell-tale staining, I am still not sure how to identify it myself. For instance, how far in should I cut to peel back the right layers to reveal the staining?)

Thank you.

I have images of the elm bark beetles and larvae below, but want to start with the stump (which might look "clean" at first pass?):



Zoom in to see the beetle hole/tunnel (first image) and larvae beneath the bark in a branch on the infected tree:


A beetle jostled into action by the cutting:


Pictures that might show relevant staining on the branch (first two) and stump (last):


Thank you for any help!
Brendan
Central Vermont

 

[Raintree]

It appears the fungal staining is not showing in the stump. No further extraction is required, I would recommend that you sharpen your chainsaw. The insect pictured is a weevil not a beetle. Continue to strip the bark, as done on the stump, up the trunk until you find streaking. I would start at the main crotch and work up the leaders.

 

[MycoMan]

Thank you, again, so much, @Raintree.

1. Hope I didn't cut way lower than necessary. Should have started right below the crotch?
2. Does this mean the disease was transmitted by beetle rather than root?
3. Thank you for the insect ID. I looked them up and am a little less ignorant now. Any sense of (the likelihood of) whether the larvae, though, are elm bark beetle? Or might they be weevil larvae?
4. I'll sharpen the saw!

 

[Raintree]

You did good, the larvae is most likely bark beetle. Unless there is a diseased elm in proximity it was an air attack not a subterranean one. The streaking in the inner bark is found below the dieback. Limbs showing wilt will be all brown under the bark.

 

[pdqdl]

Just out of curiosity, do we have a positive ID on the type of elm tree we are dealing with? Not all elm species are susceptible. I'd want to nail down the species exactly before I worried about which pathogen is munching on it.

 

[Raintree]

I believe all native North American elm species are susceptible to DED. The American elm being the most.

 

[pdqdl]

Well, I learned a bit there with some research. I had thought that several of the elms commonly found in our local forests were immune, but I have read up and learned otherwise. It's still pretty easy to find slippery & rock elms in Missouri, but the universities say they are susceptible.

Siberian elms are completely immune, so far as I can tell. They are one of the dominating varieties of mature trees found in Kansas City, although most folks have come to learn what a nuisance they are.

I did find this quote from Univ. of Ohio: "The Asiatic elms, such as Siberian (U. pumila), Japanese (U. japonica), or lacebark (U. parvifolia) elms, are much less susceptible to DED, and the disease is not considered an issue for these species."

We have a few Chinese elms in our area, and I think they are an excellent addition to any landscape, although they aren't as popular.

 

[MycoMan]

You did good, the larvae is most likely bark beetle. Unless there is a diseased elm in proximity it was an air attack not a subterranean one. The streaking in the inner bark is found below the dieback. Limbs showing wilt will be all brown under the bark.

I appreciate all you've shared in this thread, @Raintree. Thank you.

Just out of curiosity, do we have a positive ID on the type of elm tree we are dealing with? Not all elm species are susceptible. I'd want to nail down the species exactly before I worried about which pathogen is munching on it.

Good question, @pdqdl. I think it's American elm or slippery elm, but if my pics suffice to identify species, I'd love to know, too!

 

[pdqdl]

American, slippery, and rock elm I think would take closeup pictures and perhaps measurements. Slippery, I detect by grasping the leaf and feeling.

Siberian & Chinese elm I can spot with a bit better pictures.

 

[MycoMan]

Thanks @pdqdl. Not sure about this tree, as it's drying now (so I don't trust my sense of the smoothness of the leaves); but the heartwood here doesn't look reddish brown, as I read slippery elm's is.

 

[mikewhite85]

Some good information here. I recommend sending a sample to the Penn State Plant Disease Clinic to confirm the diagnosis and species. https://plantpath.psu.edu/about/facilities/plant-disease-clinic

It's a really cool free service (aside from postage). We use it frequently. Usually takes 2-4 weeks for a definitive diagnosis.