DUTCH ELM DISEASE 15 



CONTROL PRACTICES 



At present, the introduction of diseased elm trees or burl-elm logs into 

 the United States is prevented by federal quarantines. Within the United 

 States, local quarantines have been established to limit further the transit 

 of the Dutch elm disease beyond the boundaries of areas having infested trees. 



Measures to control the Dutch elm disease in the regions of the United 

 States where the disease is known to occur are directed toward preserving 

 healthy trees by the careful, prompt, and thorough eradication of all elms 

 known to be infected, and a supplementary sanitation program. 1 Whether 

 or not elms are located in an area where they are exposed directly to the 

 Dutch elm disease, it is a good practice to keep them in a healthy condition 

 and free from dead branches in which beetles might breed. However, there 

 is no complete assurance that an elm which is relatively healthy will not be 

 affected by the disease, since experience has shown that the "average elm" 

 is susceptible. 



In Europe, no general eradication program has been carried out and at- 

 tempts to control the disease by occasionally destroying affected trees in 

 various places have failed to show any constructive results. In the United 

 States, persons charged with the responsibility for the federal control program 

 have expressed the encouraging opinion that eradication of the disease in 

 this country is an attainable goal. But no program except a planned and 

 sustained campaign against the disease can possibly achieve success in the 

 eradication or even the practical control of the Dutch elm disease. 



Reports on the introduction of zinc chloride and copper sulfate into the 

 sap stream as a means of impregnating and poisoning against further attack 

 by fungi and insects indicate that a means is at hand for destroying organisms 

 in "doomed trees" whenever the actual removal of the trees must be delayed 

 for any reason. However, only trees which are definitely scheduled for de- 

 struction should be treated by this process since treated trees are certain to die. 

 Moreover, it must be borne in mind that as yet the practice of the distri- 

 bution of poisons by the sap stream in elms cannot be transferred to industry 

 in the place of pressure processes used on felled trees for the preservation of 

 heavy service woods. 



THE FUTURE OF ELMS IN MASSACHUSETTS 



At the present time the Dutch elm disease is not known to occur in Massa- 

 chusetts. However, the oldest known American infestation of the principal 

 carrier insect of the disease, the smaller European elm bark beetle, was dis- 

 covered in the vicinity of Boston in 1909. With this known carrier already 

 well established in Massachusetts, the elms of the State would be in grave 

 danger of destruction should the Dutch elm disease be introduced among 

 them. It is, therefore, most important that prompt discovery be made of 

 the first cases of the disease that may occur in Massachusetts in order that 

 immediate steps may be taken to eliminate all sources of infection. Every 

 one is urged to cooperate in the effort to protect and preserve the elm trees 

 of the State for future generations. 



1 In one area where diseased and beetle-infested trees were not destroyed until most of the 

 beetles had emerged, the diseased trees found the following year were much more numerous 

 than those found in a similar area where the affected trees were destroyed soon after their dis- 

 covery and before the beetles had emerged to any appreciable extent. 



