Non-native pest and pathogen invasions have had catastrophic impacts on an increasing number of tree species worldwide. One of the most well-known tree species restoration efforts is that of American chestnut (Castanea dentata). American chestnut was a dominant forest tree throughout much of the Eastern United States through the early 20th century. The tree was ecologically important as a source of mast for wildlife, and economically valuable for its rot-resistant lumber, high-tannin content, and edible nuts. Two non-native pathogens contributed to the near decimation of American chestnut. Phytophthora cinnamomi, which incites Phytophthora root rot, is an exotic soil-borne oomycete that attacks and kills the root systems of American chestnut. By the late 19th century, Phytophthora root rot had killed most American chestnuts in mesic sites in southeastern states. Mortality attributed to the chestnut blight fungus, Cryphonectria parasitica, was first described in 1904 in New York City, although the pathogen was probably imported into the U.S. on Japanese chestnut (C. crenata) nursery stock in the late 1800s. Most large chestnut trees throughout the species’ range were dead or dying by 1950. However, occasional large survivors and many sprouts are still found throughout the range of American chestnut.
Currently, efforts to develop American chestnuts that are resistant to the chestnut blight fungus are underway. Once blight-resistant American chestnut trees are available for planting, it will be necessary to understand how to successfully reintroduce them to forested settings. Planted chestnuts will have to contend with competing species for light, moisture, and nutrients, and will face challenges from herbivores, such as white-tailed deer (Odocoileus virginianus), insects, such as the Asian gall-wasp (Dryocosmus kuriphilus), as well as other stressors. Scientists from the Northern Research Station are studying various aspects of chestnut reintroduction to provide forest managers with methods to successfully reestablish this species to the forests of the eastern United States.