As we cross College Road, look ahead and you'll see an American
elm, its elegant wineglass shape immediately distinguishable
even in winter. This elm is a rare specimen; while elms used
to line streets in towns all over America, an outbreak of Dutch
Elm Disease in the 1930's wiped out nearly all of the species.
The disease is a fungus, carried by the elm bark beetle, which
blocks the vessels inside the tree from carrying water from
the roots to the leaves. Without water, the leaves wither and
eventually the tree dies. If diseased wood or roots come in
contact with uninfected trees, the healthy trees will quickly
become infected. Burning diseased wood is one way of halting
the spread of the disease, and some experts can inject fungicides
into the root systems of the trees, which is in some ways effective.
There is some hope for the American elm, however. The three
saplings just beyond the old tree are a new disease-resistant
variety of the species, so Wellesley may again become an elm-lined
campus. Also, other species of elm, such as the Chinese
elm, are naturally resistant to Dutch Elm Disease and grow
in other parts of campus.
Off to our right is the Dower dormitory, which recalls Wellesley's
more agricultural days; it is a converted horse barn! Right in
front of it is a huge old hemlock,
which unfortunately is also suffering from an infestation of
the Hemlock Woolly Adelgid, a pest species that was accidentally
introduced to North America. This aphid- like insect feeds on
the sap of twigs eventually killing the twig and often the tree.
Such infestations are extremely difficult to control, and the
campus will likely lose quite a few hemlocks.
Let's continue straight along College Road, and then veer off
to the right to explore a thriving ecosystem, the Wellesley meadows.