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<br />, <br /> <br />AG-BU.{)518 <br />ROIIisedl900 <br /> <br />THE DUTCH ELM DISEASE <br /> <br />DAVID W. FRENCH <br />MARK E. ASCERNO <br />WARD C. STlENSTRA <br /> <br /> <br />MINNESOTA EXTENSION SERVICE <br />UNIVERSITY OF MINNESOTA <br /> <br />David W. French isa professor, Department of Plant Pathology. Mark E. Ascemo is an assistant professor, Departmentof Entomology, <br />Fisheries, and VVildlife. and extension entomologist. Vlfard Stienstra is an associate professor. Department of Plant Pathology, and <br />extension plant pathologist. <br /> <br />All species of elms native to North America are susceptible to Dutch elm disease. The most common <br />elm species is the American elm, Ulmus americana, occurring naturally over most of the eastern Unrted States <br />from southern Canada to central Florida and west to the Rocky Mountains. It has been extensively planted, <br />will grow in a wide variety of soils, and tolerates a wide range of soil moisture. Someofthe European selections <br />are more resistant than the American elm. Siberian elm, Ulmus pumila, which has been planted in shelter <br />belts and as a shade tree, is iess susceptible but not immune to Dutch elm disease. <br /> <br />Dutch elm disease, as the name implies, was first described in the Netherlands in 1919. It spread <br />rapidly in Europe and by 1934 was found in most European countries and the Brrtish Isles. In 1930 four <br />diseased trees were found in Ohio. Ophiostoma ulmi (formally Ceratocystis ulmi), the fungus which causes <br />this disease, had been introduced to the Unrted States from Europe in logs which contained both the fungus and <br />the smaller European elm bark beetle. The European elm bark beetle, however, had been reported in <br />Massachusetts as early as 1909. <br /> <br />Minnesota's first case ofDutch elm disease was found in SI. Paul in 1961. Later the same year, seven <br />infected trees were found near Monticello, 40 miles northwest of SI. Paul. Through the 1979 season, the <br />disease was reported in 82 of Minnesota's 87 counties, with only the Northeastern and Northwestern comers <br />of the state reporting no disease. The disease is more abundant in the southern third of the State. In all, <br />Minnesota has lost between 10 and 20 percent of its 140 million elms to the Dutch elm disease. <br /> <br />1 <br />