DOUGLAS FIB PITCH MOTH. 



13 



shake " in larch above a few feet from the ground is practically 

 nonexistent, since this tree, more than any of our conifers, is, if 

 healthy, immune to insect attack, except to the foliage, and, if at- 

 tacked, is more able to repulse the onslaught from the outset. 



" Lightning ? ' has been included in the same category with " wind- 

 shake ? ' as a cause of pitch seams in Douglas fir. The theory that 

 lightning is a causative agent refutes itself by mere examination of 

 the damaged material. It is the lower two-thirds of the tree trunks 

 which are seriously pitch seamed, while the upper part is almost 

 invariably free from the defect, and it is not reasonable to assume 



I'i'.. 7. — I)cvr-lopment of a "pitch seam" only four years after the emergence of the 

 Dong) as flr pitch moth. Note the enormous growth the tree put forth to cover the 

 wound. Greatly reduced. (Original.) 



thai the electric spark would persistently leave the tops untouched 

 and so frequently injure only the part below the branches. 



Another point in (his regard is the fact that judging from the 

 Location of the seams in the trunks the trees could not have been 

 of rery great size when the defect occurred. A casual stroll in the 

 wood:- will convince the most heedless observer that it is not the 

 younger trees which are most subject to lightning. 



It i- evident from the foregoing that infestation of a i\^ 1 by the 

 Douglas fir pitch moth does not result in immediate financial loss. 



