26 MASS. EXPERIMENT STATION BULLETIN 378 



which the presence of the Dutch elm disease has been definitely estab- 

 lished, although a recent report in the eastern part of that State carries 

 the disease to a point within ten miles of the Rhode Island line; and the 

 presence of the disease in areas of infestation in New York near the Ver- 

 mont line further threatens the elms of New England States other than 

 Massachusetts. 



During the past five years close surveillance of the elms in Massachu- 

 setts has revealed certain facts relative to the Dutch elm disease problem 

 in Massachusetts. From time to time, considerable confusion has been 

 encountered resulting from popular misunderstandings, of which the fol- 

 lowing is only one example. The necessity for accuracy in describing the 

 disease as a result of infection by a fungus is frequently overlooked, and 

 leaf beetles (which contribute to tree weakening) and bark beetles (which 

 are believed to be the principal carriers of the causal fungus) are some- 

 times confused with the actual specific fungus disease. In practical ap- 

 plication, however, the association of the various factors may not be far 

 amiss if it is borne in mind that none of the factors which favor the de- 

 velopment or spread of the disease can initiate the disease independent 

 of the fungus which causes it. In a concise report' on this problem it 

 was pointed out that the disease control program in the State has con- 

 sistently worked toward the elimination of conditions which would be 

 favorable to the establishment and spread of the disease within Massa- 

 chusetts. Particular emphasis should be given to the reported danger 

 from the carrier beetle (Scolytus multistriatus Marsh.) population in south- 

 western Massachusetts, which is continuous with the beetle population 

 of the adjoining New York area where beetle-infested trees infected with 

 the causal fungus have been found. The existence of a distinct area 

 of infestation of this same carrier beetle in eastern Massachusetts has 

 set the stage for the spread of the disease there if the causal fungus is per- 

 mitted to be introduced and established widespread in the area, but 

 obviously the elms of western and southwestern Massachusetts stand in 

 more immediate danger because of the proximity of both the causal fungus 

 and the carrier beetle. 



The existence of a more or less natural barrier relatively free from elms 

 in the southwestern corner of the State, together with the aggressive 

 eradication programs for areas where the disease has been found may 

 explain the delay in the spread of the disease to Massachusetts. Outside 

 of Massachusetts, in programs for the eradication of the disease, 61,269 

 elms known to be infected with the disease fungus have been removed, 

 in addition to 5,567,334 weakened or undesirable elms which have been 

 removed because, as breeding places for carrier beetles or in some other 

 way, they constituted conditions favorable for the spread of the disease. In 

 Massachusetts, to the extent that municipalities are able to prevent the 

 accumulation of elm material favorable for beetle breeding, a real obstacle 

 to the rampant spread of the disease will be established. 



If the fullest measure of benefit from the defensive campaign waged 

 vigorously against the Dutch elm disease in the areas where the disease 

 occurs outside of Massachusetts is to be realized, therefore, only a course 

 of continued vigilance in an offensive and, if necessary, also a defensive 

 campaign against the disease is open to Massachusetts. 



' Osmus A. Vincent. The Dutch elm disease situation as it concerns Massachusetts. 

 Published among "Transcriptions of Certain Papers presented at the Seventh Annual 

 Five-Day Short Course for Tree Wardens and Foresters," M. S. C, March 30, 1940. 



