[CANUFNET] Root grafting Dutch elm disease

[Rowland, Sara]

Hi,

I used to work in the UK where we were fortunate to have a few isolated healthy elm trees left. 

Dealing with elm tree hazards - usually after the fact when the tree had fallen into the highway from a farmer's hedgerow - the concept of root transfer of the pathogen seemed highly probable as we were dealing with slender trees that had not yet reached a good size to attract the beetles. However we could not be sure in all instances that it wasn't re-infection of coppice growth from an original root system, after the original tree was removed. But root grafts do occur; there is no reason why the fungus could not spread from tree to tree in the conjoined vascular systems and we were assuming that was happening. I imagine the risk increases as the density of elm increases; generally, we had pretty dense elm all dying at the same time and about the same size and age. 

In contrast, our healthy trees were isolated and big (80cm dbh+); their isolation was a factor in their survival, away from other elms. 

Species choice should help reduce the risk; I believe Ulmus americana is fairly disease-resistant. I would suggest inter-planting with other species, to help reduce the risk even further. 

Sara
Urban Forestry Planner
City of London


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Today's Topics:

   1. Dutch Elm Disease (Mike James)


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Message: 1
Date: Thu, 8 Dec 2011 08:27:15 -0800
From: Mike James <mjames at deeproot.com>
Subject: [CANUFNET] Dutch Elm Disease
To: "canufnet at list.web.net" <canufnet at list.web.net>
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	<8CD00EC182639240BA9B8A5AC102D56B45E0E5A6 at VA3DIAXVS4A1.RED001.local>
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My client has expressed the below concern.  Is there any science to support that Dutch Elm is being passed between trees through connecting root structures?

We are wondering about Dutch Elm Disease. He heard that it spread the fastest from tree to tree when the roots are touching.We realize this would preclude us from putting two or more elms in the same tree trench. Have you ever encountered this? Is it a big concern?


Mike James
DeepRoot Canada Corp.
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