Makes me wonder if bringing home some elm could have caused it. I hope not. We've got one close to the house that we really rely on for shade. Can't say for sure if it's s red elm or not though.
I don’t know much about the disease other than there were many dead standing red and white elms in our woods when I was a kid and we would cut them up for firewood. I’ve had several white elm on my land here until about five years ago. Something moved back in and killed the rest off.
It's a fungal disease that's spread by infected bark beetles. If you bring home dead elm that still has living beetle larvae under the bark, the adult beetles could theoretically emerge and infect your trees. Unfortunately even if you don't bring home infected elm, the beetles will eventually find your trees anyway. It's just a matter of when. The highway I take to go to work has several miles of American elm stands alongside it. There are some sections where all the trees over 6" diameter are dead, and other stands where the trees are still healthy right up to about 24" or so. It's just random luck when any particular stand of elms becomes infected. I do know that elms growing further apart have a better chance of survival. Trees grown close together will root graft onto each other, so an infected tree will pass that fungus on to its neighbor. That's how decades ago city streets that were lined with elms were wiped out so fast. The fungus spread like wildfire from tree to tree from both the beetles and the root grafts. BTW, it all started in this country because some well intentioned lawmakers banned the importation of lumber. It was some resourceful furniture maker in Ohio I think that had the bright idea of importing elm logs then, which were full of infected European elm bark beetles. Decades later and here we are.
