Elm leaf gall

[lordy]

I'm wondering if this problem is regional, or nationwide?
I just noticed this leaf gall again this year on all my elms. Chinese elm, American elm, elms in pots, elms in the ground.
Apparently it is not too serious to the welfare of the tree unless the infestation is very heavy. As I understand it, an insect feeds on the leaf juices. The gall seems to be a physical reaction of the tree to being irritated by the insect. And by the time you see the gall, likely the pest has moved on. All I know for sure is that it looks like hell.

 

[JudyB]

I get them sporadically. This year none at all, don't know if it was because last year I used a systemic..... but I've had them on my elms, and just cut off the affected leaf, no problems.

 

[Oliver Muscio]

I have had them in past years--this year too, but much lighter. Perhaps it has to do with the very cold winter we just had. I understand they overwinter in the crevices of the tree's bark, and can be controlled by insecticidal spray before the leaves open, but I never remember/get around to trying it.
Oliver