dutch elm disease......

[budroe69moni]

i took down a 20 yr old american elm this morning that was in total decline. about 50% of the twings in the tree were dead and the leave were pale yellow not to mention there were about a billion woodpecker hole all over the tree!!!!!!! there were 4 of them up in there when i showed up this morning!!!!! what do you think?????? what does dutch elm disease look like??????
let me know,
budroe

 

[Acer]

Death is often sudden. It'll be fine in spring, looking groggy 1 month later(eg leaves all yellow) and dead the next. There's usually a ring of dark brown marks in the sapwood when you cut through stem and branches that show the symptoms. Lower down, on the butt, you may be able to see galleries of the beetle larvae. On the twigs, there may also be grooves in the bark, cut by the feeding beetles. It may be dutch elm if the tree's bark is rough. Young trees with smooth bark don't suffer, or so it seems. Here, they tend to be fine until 15 yrs or so, and then they keel over. Most susceptible species are U. procera, hollandica, carpinifolia (some varieties) and U. glabra. I couldn't tell you how vulnerable American elm is.

Hope that helps.

 

[tshanefreeman]

In addition to what Acer states, "...There's usually a ring of dark brown marks in the sapwood when you cut through stem and branches that show the symptoms."

This is true, but sometimes difficult and unreliable when diagnosing.

Take a stem illustrating flagging (brown, shrivelled leaves that fall prematurely or remain on the branch into the winter months) and cut it off of the tree. I find that 1/2" to 1" works the best. Starting at the cut end, peel the bark back off of the sapwood..............if the wood is still moist and slipping, this is easily done. If brownish-black streaking is evident then the fungus has infested the vascular system, but if the sapwood is a creamy white color the tree is not suffering with DED.

Note : The sapwood of a healthy branch will dry out over time and will develop a streaky appearance. This doesn't mean that the tree is infested, just that the sapwood has dried. Take your results off of the original peel.

Here's a picture to help you visualize what I'm talking about....

 

[tshanefreeman]

Thought of something else.........

One of the reasons why a cross-cut illustrating blackened vascular tissue is not realiable when testing for DED is that other disorders can have a similar sign.

For example, Verticillum Wilt will have similar vascular streaking occuring under bark on current seasons growth or show up as a ring of spots in a deeper growth ring. Therefore, making a 100% dianosis difficult.

However, a disorder such as VW typically causes elms to decline over several years and eventually die. Unlike DED, which can take anywhere from 2 weeks to a few months depending upon the aggressiveness of the fungus.