Disease is something that every history class learns about sooner or later. The Plague, the Great Flu Epidemic, Malaria, Yellow Fever and the like. Each pose significant risk, especially during the time period in which they ravaged the populations.
Tree diseases are similar in that some every person studying history should have heard of at least once; like Dutch Elm Disease.
My Community Ecology teacher pointed an American Elm tree out to us on one of our first field trips to putney. It had a trunk diameter of about 12" and was about 70% healthy. "This," he said, "Is actually an American Elm - but it is rare to see one without disease present. They were once the dominant hardwood around here, but were almost completely destroyed by Dutch Elm Disease."
Dutch Elm Disease is a fungal disease that was accidentally introduced to the United States in 1931, carried over in shipments of Elm from England to be used in furniture factories. The Elm Beetle picks up the fungus and spreads it to other trees, and ajacent trees can spread it to others by their shared roots. This once majestic tree was almost wiped out from our want of pretty furniture.
What's interesting is that I never thought I'd see another Elm that wasn't in a park or on a city street. But today when we did our prism sampling for community ecology, we found two - LARGE ones!
Our immediate first thought was, "What on earth kind of tree is that?!" followed by, "That can't be an elm... can it?"
Silly how delightful I felt knowing that we just found a rare species in the middle of the woods, in its natural habitat - but it was also that they were still hanging on, healthy, and that they would probably come back, despite our meddling. Awesome.