INSECTICIDES, PREVENTIVES, AND MACHINERY. 431 



at the base, to prevent the entrance of insects at that point. If 

 it should happen that trees are already infested, the beetles that 

 come from the trunk will be unable to get away and should be 

 killed through the netting. 



Wrapping with newspapers or tarred paper is another satis- 

 factory and tolerably effective measure. Newspapers will last a 

 season without being renewed ; tarred paper may last longer, but 

 will need retying. The tar adds nothing to the effectiveness of 

 the paper, but serves to protect it and make it more lasting. The 

 covering must be complete, so that the insects cannot get be- 

 neath it. Here also any insects already in the trunk of the tree 

 will be kept in and perish. This is applicable to all insects, what- 

 ever the size, and will prove effective in proportion to the care 

 used in fastening the paper in place. 



Instead of these materials, the German raupenleim or the 

 American dendrolene may be appHed. Both are crude petro- 

 leum products, and are in the nature of an impure vaseline, more 

 or less greasy, smooth, of a butter-like consistency at ordinary 

 temperatures, and absolutely resisting wash by rains. Applied 

 three-sixteenths of an inch thick or more to the surface of the tree 

 to be protected, they will last an entire season without] renewal. 

 The raupenleim hardens, after a time, into a crust, while the 

 dendrolene tends rather to become absorbed. No insect will 

 rest upon these materials long enough to lay an egg, and no larva 

 can bore through them to reach the trunk ; hence one thorough 

 application is an effective protection against borers of all kinds, 

 bark-beetles as well as others. As against the smaller species, 

 the materials answer to destroy the borers already in the tree by 

 preventing them from coming out through the bark. Applied 

 around the base of peach-trees, borers may be kept out, and, of 

 course, no scale insect can set where they are used. Like all 

 other mechanical protections, they are effective in proportion as 

 they form a complete covering to the bark, and probably in no 

 other way. 



Either raupenleim or dendrolene, particularly the latter, is 

 effective in preventing injury by canker-worms or other insects 

 that crawl up the trunk to reach the leaves, whether in the moth 

 state to oviposit or in the caterpillar state to feed. A broad band 

 of dendrolene, put on early in the spring, will absolutely pre- 



