430 AN ECONOMIC ENTOMOLOGY, 



CHAPTER III. 



PREVENTIVES. 



There are many insects seriously injurious to trees that are 

 difficult to reach with insecticides of any kind, and are with diffi- 

 culty destroyed in any way, and first among these are borers, 

 whatever the order to which they belong. It has been already 

 indicated under various headings what measures are available for 

 preventing and curing injury, but perhaps a grouping of what 

 may be termed preventive measures will be of some use. It is 

 the fruit grower that suffers most from boring insects, and while 

 small fruits are often attacked, the most serious and permanent 

 injury is done to trees. Peach-trees are girdled at ,or near the 

 surface of the ground by a Lepidopterous borer ; apple, pear, 

 quince, and similar trees are attacked on almost all parts of the 

 trunk, yet preferably near the base, by Coleopterous borers, and 

 almost all our fruit-trees are subject to the attack of bark-beetles. 

 Many of our shade-trees also suffer from boring insects of various 

 descriptions. It is often easier to keep these borers out than it 

 is to destroy them after they once get in, and to do that we must 

 resort to mechanical measures. The simplest as well as most 

 effective method is the use of a wire mosquito netting on apple, 

 quince, and similar trees. The parents of both the round and 

 flat-headed borers infesting these trees are quite large insects, un- 

 able to oviposit or lay their eggs through the meshes of an ordi- 

 nary mosquito netting, provided it be kept at least half an inch 

 from the bark at all points. In this way apple-orchards and those 

 subject to the same kind of injury may be effectively protected, 

 and trees once netted will need little attention, except an occasional 

 retying, for several years. The wire netting should, of course, 

 be thoroughly painted in the first place, and should have suffi- 

 cient lap, when cut, to allow of considerable growth of the tree. 

 The top must be closed by being tied tightly to the trunk, or the 

 interval between the trunk and netting must be filled with cot- 

 ton or some similar material, that the insects cannot crawl under 

 it. In like manner the ground must be hilled around the wiring 



