The answer’s in the past...dutch elm disease...
from link:
As it swept through the British countryside, Dutch elm disease wiped out 25million trees.
But among the few survivors was a specimen discovered 33 years ago by horticulturist Paul King, who decided to take some cuttings.
And now, after years of painstaking research, he has developed a tree resistant to the infection.
boy it would be nice to see streets lined with elms again. I remember them from my youth.
For some reason the Chinese hybrid elm is resistant to the Dutch elm blight.