The American Chestnut(Castanea dentata)

American Chestnut: Range• Maine to Georgia and west to

Ohio and Tennessee. (Braun, 1950)

• Commonly made up 25% or more of mixed stands

• Formed pure stands on many dry Appalachian ridgetops and near densely populated areas.Historical Range of Castanea dentata

(Saucier, 1973)

American Chestnut: Habitat

• Common on midslopes and other moderately dry soils

• Shared moist soils with many other species

• Tap root 4 to 5 ft down

“Redwoods of the East”

• Mature chestnuts could be 600 years old and average up to five feet in diameter and 100 feet tall

• Many specimens of 8 to 10 feet in diameter were recorded

American Chestnut: Ecological Importance

• Wildlife depended on the abundant crop of chestnuts

• Many species of insects fed on the leaves, flowers, and nuts

American Chestnut: Economic Importance

• Throughout much of the range chestnut had the most timber volume of any species

– Half the standing timber volume of CT

• Was the major source of tannin for leather production (6-11 % tannin content)

• Chestnuts

“From cradle to casket…”

• Fast growing – reached half ultimate height by 20th year

• Resistant to decay

• Straight and tall – often branch free for 50 feet

• Only white pine & tulip poplar could grow taller

“From cradle to casket…”

• Posts & railroad ties

• Telephone poles (65 feet)

• Construction

• Fuel

• Fine furniture & musical instruments

American Chestnut: Economic Importance

• Scientific forest management in the US was just getting started when the country lost its most important hard wood species (Smith, 2000)

• Foresters had begun to develop comprehensive plans for intensive management

• Near densely populated areas Chestnut often formed nearly complete stands

– due to rapid growth from stump sprouts

– repeated coppicing for fuelwood

Experts estimate that American Chestnut represented half the commercial value of all Eastern North American hardwoods

Pure stand of Chestnut in CT 90 years after clear-cutting, 1905.

“… the most valuable and usable tree that ever grew in the Eastern United States.”

Introduction of Cryphonectria parasitica

• American Chestnut produces a sweet but small nut 

• Chinese chestnut produces a large but generally tasteless nut

Chestnut BlightCryphonectria parasitica

Introduction of Cryphonectria parasitica

• In 1904, Herman Merkel, a forester at the New York Zoological Garden, found odd cankers on American chestnut trees in the park

Introduction of Cryphonectria parasitica

"rapid & sudden death of many branches stems & trees"

Introduction of Cryphonectria parasitica

• Thomas Jefferson – imported European or Spanish chestnut (Castanea sativa)

– grafted it onto native root stocks at Monticello.

• In 1876, a nurseryman in Flushing, NY, imported the Japanese chestnut (C. crenata). – More were brought over in 1882 and 1886.

• Chinese chestnut (C. Molissima) was brought here from Ichang in 1900. – to hybridize for ornamentals and nut production

Dispersal

• Animals and insects

• Ascospores are shot into the air after rain storms in the fall

• Rain (conidia)

• Infects trunk and branches – Only above ground parts of trees

active growth & sporulation

How does it kill the tree?

• Enters through fissures or wounds in the bark

• Grows in and under the bark, girdling the cambium.

• Kill the tree above the point of infection.

• Causes swollen or sunken orange-colored cankers on the limbs and trunks of the chestnut trees.

How does it kill the tree?

• The leaves above the point of infection die, followed by the limbs.

• Within two to ten years the entire tree is dead.

• Not uncommon to find many cankers on one tree

How does it kill the tree?

The fungus has girdled the tree and is producing yellow conidia asexual spores

Rate of Spread• Aggressive attempts to halt

the spread of the blight were made by PA and NY – removed chestnut over a large

area to halt southward spread

• In 1911-1913, the U.S. Congress appropriated special funds to enable foresters to study and control the blight

Rate of Spread

• Horticulturalists, found a blight-free area in Pennsylvania and quickly imported trees to form an experiment station

– transported the blight and created a new epicenter – Accelerated spread in PA

• Cuts in funding for Chestnut blight research:

– With the onset of World War I in 1914 – The evident futility of control efforts

• By 1926, fungus reported throughout native range

• By 1940, virtually all (an estimated 4 billion) were dead or infected with the blight

• Chestnut was the dominant wood processed at PA sawmills in the early 1920s, – salvage logging to make use of the dead and dying trees

• “…a tragic loss, one of the worst natural calamities ever experienced by this nation”

Cummulative Impacts

• Chestnut in Southern range was first affected by Phytophtera cinnamomum

• Now affecting hybrids

Cummulative Impacts

• In 1974, the Oriental Chestnut Gall Wasp (Dryocosmus kuriphilus) was brought to the US

– Female lays eggs in chestnut vegetative buds – Galls suppress shoot elongation and reduce fruiting– Heavy infestations can kill the trees (afflicts both

American and Chinese chestnuts at the southern end of their ranges)

• Threatening complete extinction

(Anagnostakis, 1994)

Current Status

• Reduced to a short lived sprouting understory tree

• Fungus can not survive below the ground.  – roots continue to live and they send up stump sprouts.   

Current Status

• Stump sprouts grow until infected– the stump re-sprouts again

• Little chance for resistance to evolve – sprouts typically killed before they become

sexually mature

– sexual reproduction rare

Last remaining stand of American Chestnut

• Trees were blight free due to isolation until a canker was found in 1986

• Now over 1600 cankers are present on 530 trees.  

• Virus was introduced in 1992 – not successful

• Largest living (>3 ft dbh) about 20 miles east of La Crosse, WI.

•10 chestnuts planted in 1885

• Seeds propagated around 50 acres and more than 3000 trees

Where are we now?• Upper slopes – scarlet oak,

hickory, black gum

• Mid slopes – red and white oak, red maple, & hickory

• Coves – Poplar, hard maple, beech

• Understory - American chestnut sprouts still persist, however they become infected between 1-12 yrs of age.

American chestnut resistance

• Breeding programs

– Scions were grafted into chestnut rootstocks to

establish seed orchards

• Seeds and seedlings have been distributed that have

low levels of blight resistance by artificial inoculation

with a standard virulent strain