Dutch Elm Disease in Illinois 



J. Cedric Carter 



DUTCH ELM DISEASE has killed millions of elm trees since 

 its introduction into the United States. It was discovered at 

 Cleveland and Cincinnati, Ohio in 1930, and in Connecticut, Mary- 

 land, New Jersey, and New York in 1933. Although the disease ap- 

 peared at Indianapolis, Indiana in 1934, it was not found in Illinois 

 and Michigan until 1950. Since 1950 the disease has spread rapidly 

 throughout the midwestern states and by 1966 was present in 30 

 states, the District of Columbia, and three provinces of Canada. It 

 occurs from the Atlantic Coast west to Nebraska and Colorado and 

 from Georgia, Arkansas, and Oklahoma north to the Canadian prov- 

 inces of Ontario, Quebec, and New Brunswick. By 1959 the disease 

 was found in every county in Illinois. 



Some Illinois cities lost nearly all of their elms to Dutch elm 

 disease in a period of 10-12 years. After a rapid buildup of the disease 

 during an initial period of 5-7 years, losses have ranged from 15 to 

 20 percent of the existing elm population each year. These losses 

 have continued until about 95 percent of the elms once present have 

 been killed. This rate of dying m.eans that, in a city that once had an 

 elm population of 20,000 trees, 19,000 have been killed. 



The cost of removing 19,000 elms at $75 per tree is $1,425,000, 

 and removal cost of $75 per tree is less than the average paid by 

 many cities. A control program that holds the annual loss of elms to 

 2 percent or less of the current elm population is desirable because 

 it avoids exorbitant tree removal costs, prevents devaluation of real 

 estate, and ensures the continued enjoyment of elms as shade trees. 



SYMPTOMS AND CAUSE 



The first noticeable symptoms of Dutch elm disease are wilting, 

 curling, and yellowing of leaves on one or more branches, a condi- 

 tion often called "flagging." These symptoms are followed by dying 

 and browning or premature falling of leaves, and death of affected 

 branches. Some affected trees first show wilting of leaves on one or 

 a few branches (Fig. 1), followed by wilting of leaves on additional 

 branches and finally death of the affected trees. Elms affected in 

 this manner in early summer may die during the same growing sea- 

 son. Those affected in late summer may die during the winter, soon 

 after leaves appear in the spring, or slowly over a period of a year 

 or more. Other elms may show foliage wilt on most or all of their 

 branches at one time and die within a few weeks (Fig. 2). Trees that 



