Borers and Bark-beetles 



147 



run into the hole, or the worm may be cut out and the scar 

 treated like any other wound. 



In any case, tedious individual treatment is necessary, 

 there being no wholesale method. Hence, where borers 

 are to be feared, preventing their entrance by protective 

 covers is the preferable method. Against the larger borers 

 a wire mosquito netting, placed around the trunk loosely, 

 so as not to touch the bark, set into the ground at the base 

 and tied at the top, prevents the beetles from laying their 

 eggs either under the bark scales or in a gnawed hole. This 

 device also prevents beetles in the trunk from emerging, 

 leaving them to die without chance of reproduction. On 

 branches, tarred paper or even newspaper will answer the 

 same purpose, or else whitewash, to which Paris Green has 

 been added, can be thoroughly applied with a knapsack 

 pump through a Vermorel nozzle. But this must be renewed 

 every week or two until the middle of July, when the danger 

 from flat-headed borers is past. Still better is an applica- 

 tion of dendrolene or "insect lime", which keeps effective 

 for the season if appHed properly at the right time. But 

 all these measures are practically undesirable, and even- 

 tually removal of the infected tree is the only resort. 



The most insidious and least amenable to remedies are 

 the bark-beetles, the larvae of which, minute white grubs, 

 burrow in the soft wood and cambium layer under the bark, 

 destroying the cambium; and since several broods are made 

 during the same season, their numerous galleries eventually 

 girdle and kill the trees. Little round shot-holes show the 

 inlet and outlet of the small black or brown beetle, but 

 when the broods of larvae have been at work for some time, 

 the bark is loosened and can be peeled off without resistance. 



Since these beetles hardly ever attack healthy trees, pre- 

 ferring those which have been otherwise weakened or under- 



