Like humans, trees are susceptible to disease. For example, the tall American sycamore (Platanus occidentalis) just behind Agnes Scott Hall suffers from bacterial leaf scorch. Sometimes the effects of a disease can be catastrophic. Early in the 20th century, an imported blight killed three to four billion American chestnuts (Castanea dentata) within just a few decades, making this species all but extinct in forests that it once dominated. The American elm (Ulmus americana) was threatened with a similar fate, but its story has a happier ending.
Long the quintessential town tree, the American elm met its match in Dutch elm disease. This disease frustrates the tree’s primary means of defense: sealing off diseased wood. Hundreds of communities have lost their stately, vase-shaped street trees. Fortunately, some individual elm trees are resistant to the disease. From these, botanists have developed cultivars like those planted here on either side of the brick path. These elms are genetic clones of a tree in Princeton, New Jersey.
Ironically, as human activities transport tree diseases around the globe, trees themselves can help protect our health. Native Americans used the inner bark of the slippery elm to treat many ailments, including wounds, sore throat, and indigestion. More recently, researchers have developed several anticancer drugs, such as taxol, from trees.