Pennsylvania Game News - May 2012 - 10

THE American dogwood, easily recognized in the spring, is today threatened by dogwood anthracnose, a fungal disease that has caused dogwood mortality up to 80 percent in some areas.

that includes stuffing made with wild chestnuts. As I thought about the disappearance of the chestnut trees, I was reminded of another tree that was once common in many parts of America. Most of us over the age of 50 remember seeing elm trees in our neighborhoods. In fact, many towns and villages have Elm Streets named no doubt from the high arching elms that once shaded them. It also was under elm trees that white man and Native Americans smoked the peace pipe and brokered their deals; even William Penn and Daniel Boone were connected with so called “treaty elms.” For the most part, elms are gone, victims of Dutch elm disease, a fungus thought to have come from the Himalayas. Introduced into the U.S. in the 1930s, Dutch elm disease attacks the tree’s vascular system. It spreads though the xylem vessels in the sapwood, which conduct water and nutrients from the roots to the leaves. Dutch elm disease got its name because it was Dutch scientists who identified it in 1917. After its discovery it quickly spread throughout Europe, wiping out millions of trees. The disease is actually caused by two fungi, a non-aggressive strain and an aggressive strain. It is believed these strains were introduced to the U.S. through shipments of unpeeled veneer logs from Europe. The disease quickly
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spread through most of the country, killing an estimated 46 million elms. Around 1945 the disease was introduced in North America for the second time, when it arrived in a shipment of logs from Canada. This time, more than half the remaining elm trees in eastern Canada and the U.S. became infected and were subsequently lost, because native elm trees did not evolve a resistance to the disease, and because the deadly fungus can spread in several ways. The primary way the fungus is spread is by one of two beetles, the European bark beetle and a native bark beetle. The microscopic spores of the fungus are spread as the beetles tunnel under the bark of healthy elm trees. The fungus can also spread underground from the roots of one infected tree to another, and by infected shovels, rakes and other hand tools. Although the American elm has disappeared from much of its former range, its future looks bright. In 1995 scientists announced the successful cloning of two new elm strains resistant to the disease, “Valley Forge” and “New Harmony.” According to the USDA, Valley Forge has performed well in Ohio, Maryland and the District of Columbia, while the New Harmony strain has grown well in Georgia, Maryland, Minnesota, New Jersey, Ohio, Oklahoma and Pennsylvania. Scientists say neither strain is completely immune to Dutch elm disease, but both have unusually high levels of tolerance and are now available for planting. For me, flowering dogwood signals the end of winter. Not long ago, it was easy to spot blooming dogwood trees, even across valleys, because they grew not only along field edges but throughout forest understories, but not anymore. Today the dogwood is under siege, and it has been
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Pennsylvania Game News - May 2012

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