THE DUTCH ELM DISEASE 



Since 1930, when the Dutch ehn disease caused by the fungus, Ceratostomella 

 tilmi (Schwarz) Buisman, was first discovered in the United States, all persons 

 interested in our shade trees have become increasingly alarmed as the number of 

 ehns known to be affected has steadily mounted. As the name implies, the Dutch 

 elm disease was first observed in the Netherlands; and, since its discovery in 1919, 

 thousands of elms in European countries have been killed. The disease exists 

 throughout the extensive range of climatic and soil conditions included in the 

 Netherlands, France, Italy, Austria, Belgium, Switzerland, Germany, Poland, 

 Czechoslovakia, Balkan States, and Great Britain. The disease is widely dis- 

 tributed in England but has not as yet been found in Scotland. 



In both Europe and North America, the only continents where the disease has 

 been observed, elms and trees of the closely related genus Zelkova are apparently 

 the only hosts upon which the disease occurs in nature. A few species of elms are 

 reported to be resistant, but none is known to be immune; and the American 

 elm ( JJlmus americana L.) is very susceptible. 



From 1930 to 1932 the known cases of the disease in America were limited to 

 less than a dozen trees in Ohio. Later the disease was found in the mid-Atlantic 

 States and southern New England. Elms in Massachusetts were first known to 

 be affected in 1941 when one diseased tree was found in the town of Alford, in 

 Berkshire County. In 1942, six diseased trees were found in the State: three in 

 Egremont, one in Great Barrington, one in Westfield, and one in Sheffield. These 

 trees were destroyed immediately, and in order to further protect disease-free 

 elms, concerted effort has been directed toward the prompt disposal of all freshly 

 cut elm wood. This is the most practical control that can be employed effectively 

 in checking the increase in population of bark beetles which spread the causal 

 fungus. Since the fungus is virtually a prisoner within an affected tree, it cannot 

 spread significantly except as it is carried from a diseased to an uninfected tree by 

 a vector. The best evidence indicates that the smaller European elm bark beetle 

 {Scolytus midtistriatus Marsh.) is the principal carrier insect. This insect invades 

 the bark of weakened trees or freshly cut elm wood, where eggs are laid in gal- 

 leries engraved between the bark and the wood. Upon emergence, beetles feed 

 for a short period of time on healthy elm twigs and in this manner may spread 

 the disease to previously healthy trees if the feeding beetles come from galleries 

 in which the fungus is present. At this writing (December 1942), the beetle is 

 known to occur in Springfield, West Springfield, and Westfield in Hampden 

 County, and widely in Berkshire County, in addition to the originally known 

 eastern Massachusetts infestation which now includes most of the area east of 

 Worcester County. Possibly the native elm bark beetle {Hylurgopinns rtifipes 

 Eich.), which is generally distributed in Massachusetts, may also spread the 

 disease. If so, the prompt disposal of cut elm wood is doubly necessary. 



Therefore, all agencies and individuals whose work brings them into contact 

 with freshly cut or drying elm wood, which is highly attractive to bark beetles, 

 are urged to dispose of this wood promptly by burning, unless there is complete 

 assurance that the bark will be removed immediately after the wood is cut. Tree 

 wardens, foresters, arborists, fire wardens, highway departments, state depart- 

 ments, and public utilities have cooperated generously in aiding in this practical 

 method of protecting disease-free elms. As in the case of all fungus diseases and 

 insect pests of plants, however, unbroken continuity of the program is most 

 essential. Experience has shown the interruption of investigational and control 

 programs to be a costly mistake. The elms of Massachusetts are a priceless 

 possession of all the people of the Commonwealth. 



