In speaking with a Dendrologist, today I learned that the primary factor here is the close proximity of "planted" elm trees. Elm bark beetles don't travel far

In speaking with a Dendrologist, today I learned that the primary factor here is the close proximity of "planted" elm trees. Elm bark beetles don't travel far on their own, so in a typical forest environment, elm groves are protected, or buffered, by a variety of surrounding tree types, the distance between groves, and the natural order of things. Whereas, in (sub)urban areas, elm trees are planted up and down residential streets, in close proximity, with no buffers in between. There's no winning this one.