PPDL Picture of the Week for
November 12, 2012

Chestnut Blight

Janna Beckerman, Associate Professor, Botany & Plant Pathology Dept, Purdue University

As the holidays approach, we get a seasonal reminder of that exotic invasives have changed not only our landscape, but our culture whenever we hear Nat King Cole sing the words, “Chestnuts roasting on an open fire…”

Before emerald ash borer and Asian longhorned beetle, and before Dutch elm disease, the American chestnut was the major overstory tree in the eastern portion of North America, from Maine through the southeastern portion Indiana, continuing to southern Alabama, and west into Arkansas (Figure 1). The trees were valued for their rot-resistant lumber, tannins for leather curing, and for their nuts (Figure 2), which were considered better quality than their Asian and European chestnut cousins. They also served as a staple for rural families, in addition to an important food source for wildlife.

Chestnut blight, caused by the fungus Cryphonectria parasitica, was discovered in North America in 1904. Within 4 years after its discovery in the Bronx zoo, the disease was detected in Connecticut, Delaware, Maryland, Massachusetts, New Jersey, Pennsylvania, and Virginia. By 1940, it was found wherever the chestnut once lived, and reduced a major component of the forest overstory into a coppice of suckering stems that usually became afflicted with the blight, reducing a forest giant to an understory shrub. The first observed symptoms of chestnut blight include yellowing of leaves followed by wilting of the foliage. The leaves continue to die as the branch or stem blight expands, with bright orange fruiting bodies erupting through the bark (Figure 3). Chestnut blight can still be found on the coppice clumps of remaining American chestnut even today.

Today, breeding efforts continue to identify blight resistant chestnut trees for Indiana and United States. Blight resistant American chestnut trees are the result of crossing American chestnut with Chinese chestnut, and then crossing those resistant seedlings back to American chestnut for three generations to create trees that are 15/16th American chestnut and 1/16th Chinese chestnut. Trees like this are being released throughout the country, including in Hoosier National Forest. Hopefully, future generations will have American chestnuts, roasting on an open fire.

Other resources:

American Chestnut Trees Return to the Hoosier National Forest

Chestnut Blight

Indiana Chapter of The American Chestnut Foundation

Click image to enlarge

Figure 1. It's hard to image trees this large today: Dead chestnut tree c. 1920, in Tremont Falls, TN. Image courtesy of Great Smoky Mountains National Park Library.

Figure 2. Spiney chestnuts are ripe when they fall, and generally open after first frost. Gloves recommended!

Figure 3. Chestnut blight. Photo by Janna Beckerman.

Purdue Plant & Pest Diagnostic Lab Purdue Cooperative Extension Service