The Chestnut Blight was first noticed in New York at the Bronx Zoo in 1904, but probably was first brought
into the northeastern U. S. sometime in the 1800s on Asiatic Chestnut trees (Chinese Chestnut and/or Japanese Chestnut). It spread like wildfire from the northeast southward killing almost every American Chestnut tree
throughout the eastern U. S. Our Chestnut trees had little or no resistance to this exotic
fungus (Cryphonectria parasitica), because the American Chestnut had evolved in North America
isolated from the Asiatic Chestnut trees which had evolved with this parasitic fungus and had
developed some resistance to it. By 1950, billions of American Chestnut trees in the eastern U. S.
had been killed by this exotic fungus. Now, only rare sprouts remain, clinging to life in the forests--puny
relicts of the giant trees they once were. Very rarely, a sprout lives long enough to flower and produce
nuts but they are usually infertile from lack of cross pollination; even this is cause for celebration among
American Chestnut enthusiasts, but the euphoria is short-lived because these fruiting trees usually die just
a few years later. Most do not live more than 15 years due to the blight and/or other diseases; competition
from nearby trees also takes a toll. Most of the trees died from the blight in the 1930s and practically all
were gone by 1950, but the blight did not directly harm the roots. The king of coppice sprouted back with
a vengeance. Some Chestnuts have repeatedly died and sprouted again from their root collars for the past
70 years, but the vigor and number of these sprouts have been declining. After all, they can't be expected to
forever battle the blight, other diseases such as root rot, ravenous insects, browsing by deer, competition
from other trees, unfavorable weather conditions and habitat destruction by humans. It was hoped that in
some parts of its natural range there would be pockets of Chestnuts that would have resistance to the disease
and would be reproducing successfully from their nuts, not just by sprouting. To my knowledge, such populations,
sometimes called the "holy grail" by American Chestnut fans, have never been found. It appears that human
intervention will be necessary to restore the American Chestnut to the forests of the eastern U. S.

There are some naturalized American Chestnut populations in Canada, and the northwestern U. S. that
were established from seeds the settlers took with them as they migrated. These trees are not resistant to the
blight, but they thus far have been sufficiently geographically isolated from the blight fungus in the East
that they have attained large size and are reproducing by seeds. There are some populations in Wisconsin
(outside of the Chestnut's original range), but in recent years the blight has found them and many of these
trees are falling despite efforts to check the disease.

excerpt from:

Resurrecting the American Chestnut
Authored by Joe Schibig, Biology Professor
Supported by Volunteer State Community College, Gallatin, Tennessee