1920-21 DEPARTMENT OF LANDS AND FOEESTS. 329 



imperfectly understood diseases of balsam, namely "red branch" and a twij,' 

 blight. 



" Eed branch " of balsam has frequently been noticed by foresters and lumber- 

 men and various explanations have been offered in accounting for the phenomenon. 

 Dead, red-needled branches located here and there throughout a balsam tree are 

 conspicuous objects against the dark green setting of normal living foliage and 

 could not escape observation. One of the theories most frequently advanced in 

 explanation is snow pressure, the breaking or cracking of the bark at the base of 

 the branch due to the weight of accumulated snow. 



Aside altogether from any discussion of the part played by snow pressure 

 elsewhere, an inviestigation of " red branch " of balsam in the Temagami Forest 

 Reserve has demonstrated that its most frequent cause in that area is not snow 

 pressure, but a combination of factors not before suggested, namely, insect-wound- 

 ing and frost. 



An examination of the branch at the base of the dead portion almost invariably 

 shows a more or less extensive spot from which the bark has been removed, a 

 ragged-edged wound at once suggesting the gnawing of some small animal. This 

 spot is usually on the under side; it never extends more than ha^lf way around 

 the branch and usually much less, so that the branch is not girdled. It may 

 extend indefinitely towards the tip of the branch, commonly for not more than 

 half an inch, but sometimes for several inches. Occasionally the leader is des- 

 troyed in the same way as the branches. 



The wound in itself is not sufficient to cause the death of the branch. This 

 was proved by similarly removing the bark with a knife from healthy branches 

 in July of 1919. The wounds healed before the end of the season, and they 

 showed no ill effects of their maltreatment throughout the summer of 1930. But 

 when the wounding takes place so late in the season that there is no time left for 

 covering the edges of the wounds with new tissues the result is different. Twenty- 

 five branches were wounded in the same manner in October, 1919. Withont 

 exception every one of these branches died from the point of wounding outward and 

 their foliage was red by the following May. 



The cause of the wound is a large bark beetle, identified by Dr. J. M. Swaine 

 as Monochamus scutellatus. This beetle occurs abundantly in the Reserve on 

 jack pine, where it gnaws the bark in like manner, but either because of a thick 

 covering of resin or because the wounding is earlier in the season the branches 

 attacked are rarely killed. 



A few instances of what appeared to be snow pressure came to hand, but in 

 such cases none of the bark had been destroyed. Likewise instances of removal 

 of the bark by rubbing, or of the pulling off of low-placed twigs on small branches 

 in the fall or winter followed by the death of the branches are not infrequent. 

 But the prevalent cause of the very common " red branch '* in the Temagami 

 Reserve is the combination of beetle-gnawing and frost, as described above. 



(6) A Twig Blight of Balsam. 



Especial attention is drawn to a twig blight of balsam that appears to have 

 been overlooked or to have been confused with the work of the spruce bud worm. 

 It is plainly not an insect injury though the exact cause is not yet known; au 

 investigation of it is being undertaken. The new growth only is affected, and the 

 injury may involve the entire twig, killing the bud as well as the needles; or 

 the bud may escape, ])ut all or only a few of the needles here and there may 



