A little over 100 years ago, the American chestnut (Castanea dentata) grew in abundance along the eastern United States. It dominated the slopes of the Appalachian Mountains. The tree stood up to 100 feet in height with a trunk diameter of 10 feet, according to Volunteer State Community College. Large, nearly pure stands of the trees could be found in abundance. Unfortunately, a fungal disease known as the chestnut blight struck the trees. In less than 40 years, the blight killed almost all the trees. Only a few isolated clumps remain in the Pacific Northwest which have never been affected by the blight.
In 1904 the blight, known as Endothia parasitica, was brought into New York from the Orient. The blight first affected the American chestnut tree's habitat within the New York Zoological Garden. It was first observed by a forester, Herman W. Merkel. The New York Botanical Garden had planted Asian chestnut trees on the grounds and the blight was believed to have stemmed from them.
The blight fungal spores are spread to the American chestnut tree's habitat by the wind and through rain. The fungus enters the tree and forms cankers on the limbs and trunk. The fungus girdles the tree and causes the branches to die. Within two to 10 years of infection the entire tree dies, according to the Appalachian Woods. The blight spread northward from New York into Connecticut and Massachusetts and than into New Jersey. By the mid-1920s, the blight had reached as far south as the habitat of the American chestnut tree in Georgia.
Despite the death of the American chestnut tree, the dead trees remained standing in their habitat throughout the eastern U.S. The trees stood, dead and leafless, for decades without breaking down and deteriorating. This enabled the wood to be logged. Up to 10 years after the blight killed the tree it was still logged and the wood used with great success. As the dead chestnut trees stood for years they became infected with tiny borers. The borers produced tiny holes in the wood. The wood became known as "wormy chestnut" and was popular for the manufacture of picture frames.
Even though the entire upper portion of the American chestnut tree died, its roots still remained alive and tried to reproduce new, healthy trees in the American chestnut habitat. The tree's root system sends up saplings that begin to thrive but they eventually become infected with the blight and succumb. Small saplings and trees still grow throughout the Great Smoky Mountain range but they will all eventually die from the blight, which still exists.
Ongoing research tries to restore the American chestnut tree within its native habitat. Back-crossing and interbreeding of the American chestnut and Asian chestnuts continue in an effort to create a tree that is blight resistant. Unfortunately, none of the newly resistant hybrids are available in a large enough scale to be planted in the regions where the American chestnut once flourished.
Fungicides have been developed which show promise in treating the blight in seedlings which have recently contracted the fungus. A nonvirulent strain of the blight has also been discovered which may lend hope by inoculating the young American chestnut with the nonvirulent strain to offer it immunity. Hypo-virulent strains inoculated into an American chestnut tree allow the seedling to grow rapidly and quickly be able to produce ample nuts with only minimal symptoms of the blight.