THE RED ROT OF CONIFERS 5 



at its general appearance does not tell him, he sounds the tree with his 

 axe to see if it is worth felling. To the untrained person, however, 

 considerable observation is necessary to judge with any degree of ac- 

 curacy whether a tree is or is not diseased. Of course the discovery 

 of a fruiting body (Plate III) is a sure indication, but aside from this 

 evidence one can judge only from general appearance. Perhaps the 

 most reliable indication, at least in the pine and spruce, is the abnormal 

 exudation of pitch or resin from old knot-holes, or, if the disease has 

 progressed far enough, from other points on the bark. This pitch 

 drops down the sides of the tree and is very noticeable, as is shown 

 in Plate II, upper left hand corner. If the fungus has invaded the 

 trunk of the tree sufficiently to affect its health seriously, a general 

 paleness of the bark and even of the foliage ensues. These evidences 

 are not confined to any particular part of the trunk. The very first 

 stages of the disease are betrayed by this pitch exudate. Suspected 

 trees manifesting these early evidences of the malady were cut, which, 

 upon internal examination, revealed only the red color of the heart- 

 wood, which is the result of the first structural change brought about 

 by the fungus. Later in the progress of the disease all the external 

 evidences become intensified so that advanced stages are detected more 

 easily. 



III. SPECIES AND CONDITION OF TYPES ATTACKED 



Susceptibility of species. Red rot is found commonly in the five 

 soft wood species: pine, spruce, hemlock, balsam and tamarack. Von 

 Schrenk (2) states that "of the five trees the tamarack seems to be the 

 most readily attacked, the spruces come next and the balsam fir last." 

 Although tamarack is not as plentiful in Vermont as the other species, 

 the writer's observations tend to confirm Von Schrenk's statement as 

 to its susceptibility. In regard to other species, however, the writer's 

 study of his data leads him to conclude that, in Vermont at least, white 

 pine is second in susceptibility, while spruce, hemlock and balsam are x 

 susceptible to invasion in about the same degree. It was noted that 

 spruce in mixed stands appeared more prone to attack than when grow- 

 ing in a pure spruce stand. This is not easy to explain, unless it may 

 be due possibly to better self-pruning and to more healthy and favor- 

 able silvicultural conditions. 



Pure white pine stands showed greater amounts of red rot than 

 did any other type. Where the disease was present at all in the white 



