Dutch elm disease
Dutch elm disease is a destructive fungal condition primarily affecting elm trees, leading to rapid decline and death. It is caused by the fungi Ophiostoma ulmi and Ophiostoma novo-ulmi, and is mainly transmitted by elm bark beetles, but can also spread through root connections and contaminated tools. The disease first emerged in Asia and was identified in the Netherlands in the early 1920s, earning its name shortly thereafter. In the United States, it was first detected in Cleveland in 1930, with significant outbreaks occurring in the New York City area by 1932.
The federal response included quarantine measures and a tree removal program, yet the spread of the disease continued, exacerbated by environmental factors like the Great New England Hurricane of 1938. By the end of the 1930s, millions of elms had been lost, significantly impacting urban landscapes that once featured these majestic trees. The disease continued to spread throughout North America, reaching the West Coast by the 1970s and advancing into Canada in the 21st century, although certain regions have managed to remain disease-free. The decline of elm trees has influenced urban planning and community identity, as many towns historically celebrated their elm-lined streets.
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Dutch elm disease
Disease caused by a fungus that kills elm trees
Dutch elm disease came to the United States from Europe in elm logs used in the furniture industry. American elms proved to be particularly susceptible to the disease. First identified in Ohio in 1930, the disease was found in seven eastern states by the end of the decade. Subsequently, it decimated elm trees throughout the United States and most of Canada.
Dutch elm disease quickly kills elm trees. Leaves of infected trees wilt, turn dull green and then yellow or brown, and may drop early. Young trees may die within months, while older trees may take two years to succumb. The disease is caused by a fungus (Ophiostoma ulmi or novo-ulmi) and is spread primarily by elm bark beetles. It can also be spread by root-to-root contact and contaminated pruning tools.
The disease originated in Asia and came to Europe during the 1910’s. Its cause was first identified in 1921 in the Netherlands; hence its name. In the late 1920’s and early 1930’s, it came to the United States. In 1930, it was first identified in Cleveland, Ohio, where the outbreak was small and could have been controlled. However, in 1932, a major outbreak was discovered around New York City. In 1933, twelve hundred infected trees were identified within forty miles of the city, in parts of New Jersey, New York, and Connecticut. In 1934, more than seven thousand diseased trees were found in this area.
On October 21, 1933, an embargo barring the importation of elm logs was enacted. In addition, a domestic quarantine was instituted to prevent movement of elm plants or parts of plants beyond the outbreak area. The federal government created a program to identify and remove diseased trees. Scouts were hired under the Works Progress Administration and the Civilian Conservation Corps. However, resources were insufficient to halt the spread, which was exacerbated by the Great New England Hurricane of 1938. Hundreds of thousands of elms were destroyed and left to rot, providing a massive habitat for the elm beetles that carry the disease. By the end of the 1930’s, more than five million elm trees had been removed in areas encompassing parts of New York, New Jersey, Connecticut, and Pennsylvania. Infected trees were also identified in Ohio, Indiana, and Maryland.
The federal program slowed the progression of the disease. Nonetheless, the disease spread up and down the East Coast of the United States and headed west, reaching the Rocky Mountains during the 1950’s and the West Coast during the 1970’s. At the beginning of the twenty-first century, it continued to spread north into Canada, although an aggressive campaign has kept the provinces of Alberta and British Columbia disease-free.
Impact
Prior to the 1930’s, elm trees were planted along streets and walkways as windbreaks and shade-providing canopies. It was the preponderant urban tree at the time and many towns were proud of their elms, hailing themselves “Elm Cities.” Because the American elm was particularly susceptible to the disease, the 1930’s marked the beginning of the end of elm-lined streets, walkways, and parks in North America.
Bibliography
Campanella, Thomas G. Republic of Shade: New England and the American Elm. New Haven, Conn.: Yale University Press, 2003.
Sinclair, Wayne A., and Howard H. Lyon. Diseases of Trees and Shrubs. 2d ed. Ithaca, N.Y.: Cornell University Press, 2005.