DUTCH ELM DISEASE 7 



reduced annual growth in these instances is not to be distinguished from the 

 stag-head commonly associated with various other troubles affecting elms. 



Sometimes affected trees have been found in a group in which the disease 

 had apparently spread from a central point. 



The symptoms of the Dutch elm disease to be observed in winter are relatively 

 few and not such as to be of much assistance in recognizing trees which are 

 affected with the disease. Trees infested with bark beetles, trees which are 

 stag-headed, trees which have dead branches, trees which show excessive 

 suckering, and trees which fail to set flower buds or have dead leaf buds may 

 be suspected of being affected with the Dutch elm disease, and the wood of 

 such trees should be examined for further signs of the disease. 



Figure 2. Diagonal and Cross Sections of Young Elm Twig and Branch Affected with 

 the Dutch Elm Disease. 



In the latter, the brown discoloration appears in the photograph as a dark concentric ring 

 about \ 2 inch from the outside circumference of the outer bark. In the former, the discoloration 

 is shown as an incomplete ring 1-16 inch interior to the limits of the cut surface of the twig. xlM. 



A diagonal cut made through a twig affected with the disease shows a 

 brown discoloration in the sapwood (Figure 2). Various patterns of dis- 

 coloration may be associated with the disease. This darkened area may or 

 may not be confined to one annual ring or a part of one annual ring; it may 

 include the entire width of an annual ring or it may be limited to a narrow 

 circle or semicircle in the spring wood, in the summer wood, or in both; and 

 if it appears in more than one annual ring, these rings are not necessarily of 



