The American chestnut was a major species in the temperate forests of North America. In 1904 the infamous chestnut blight was introduced to the continent in New York City. By 1940 the disease had devastated the chestnut population along the eastern third of the United States. Large-scale tree death resulted in the loss of half of the total value of hardwood stands. Presently there are no wild adult chestnut trees in the United States. All of the destruction was caused by a single fungal species Cryphonectria (Endothia) parasitica. Like most tree fungi, C. parasitica  takes advantage of wounds or other fissures in the bark. Once past the bark the fungus grows in the cork cambium causing either a swollen or sunken canker to form. Coloration of the sore can range from reddish-orange to yellow green. The canker starts to create a fissures in the bark, eventually girdle the steam leading to wilting and death of tissue beyond the original sore. The extensive damage and stress causes tree death in all cases.
     The fungus is highly transmissible; when spores are release they are spread through many vectors including by insects, birds, water, and air. The fungus will survive in dead chestnut trunks as well as infect oak trees on occasion. American chestnuts as a species are still clinging to life through sprouting, however once the bark is fissured the small tree is infected and is dead within a few years. There are no community scale cures for chestnut blight. Individual trees can be treated with an anti fungal. A new method is to make the wild type C. parasitica  compete with a strain that has double standard RNA (ds-RNA). The ds-RNA attacks the wild type stain of the fungus leaving it hypovirulent. Although promising, this technique has not been approved for wide scale use (Agrios, 1997).