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Of chestnuts and cherries August 30th, 2015 by

Do you ever wonder why they stop you at the airport or the border crossing and ask if you have any plants?

The American chestnut was once the largest and most common tree in the eastern woodlands of the USA. Its loss led to a greater understanding of the importance of quarantine to protect agricultural and forest trees.

In the early twentieth century, the chestnut blight fungus arrived in North America from Asia. Chestnut blight was first spotted in 1904, in the Bronx Zoo. The chestnut trees started to die, much to the dread of the American people, who liked the tall, handsome tree, and valued its wood for furniture making. The disease was widespread by 1911 and the trees were basically gone by the 1950s.Here and there, a few ancient chestnut stumps still sprout branches. A sixty acre (24 hectare) stand planted by settler Martin Hicks, in West Salem, Wisconsin (outside of the tree’s natural range) is the largest remnant left.

Rescue efforts failed, but the US Department of Agriculture (and more recently the American Chestnut Foundation) never gave up, and have recently bred a resistant variety of chestnut, which they are planting on public forest lands, within the chestnut’s historical range. The new tree is 15/16’s American, but was crossed with Asian trees that are resistant to the blight. The new variety seems to be resistance to the blight.

At least the chestnut disaster was a learning experience. In 1910, the Japanese government gave the US a gift of 2000 ornamental cherry trees. American plant pathologists in Washington inspected the trees, observing that some of them had insect pests, fungi and nematodes. The Department of Agriculture burned the entire shipment from Japan, to protect American fruit trees from disease. It was an early experience with quarantine, isolating plant imports to protect the receiving country from disease.

Destroying the trees was the right thing to do from an agricultural point of view, but it was a diplomatic crisis. The State Department telegraphed a note of apology to the Japanese government. It was a model of frankness and tact, acknowledging that “It has been found necessary to destroy all of the cherry trees presented by the municipality of Tokyo for the use of this city. The reports of several experts of the Department of Agriculture show the trees to be badly infested with the root gall worm, certain fungus diseases and insect pests, some hitherto unknown in this country, whose introduction might result in future in enormous detriment to trees and agriculture generally.”

flowers and Washington monumentThe Japanese graciously responded by sending 3,000 more cherry trees, healthy ones this time. They still bloom gloriously once a year around the Tidal Basin Pond, in a large, but neat circle between the Jefferson and Lincoln monuments, in Washington DC. Diplomatic and agricultural disasters were avoided.

The tragedy of the American chestnut taught plant pathologists the importance of inspection and quarantine, which they used in the case of the Japanese cherry trees, still blooming a century later. Now most countries have airport and border inspectors to screen plants coming into the country. It may seem like an inconvenience, but it is a small price to pay to keep the trees standing.

Further reading

Campbell, C. Lee, Paul D. Peterson & Clay S. Griffith 1999 The Formative Years of Plant Pathology in the United States. St. Paul, Minnesota: The American Phytopathological Society. 427 pp.

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