43° 



AX ECONOMIC ENTOMOLOGY. 



CHAPTER III 



PREVENTIVES. 



There are many seriously injurious insects which it is difficult 

 to reach with insecticides of any kind or to destroy in any way ; 

 and first among these are the borers of all orders. Special 

 destructive, remedial, and other measures have been indicated 

 throughout this work, where the offending species are described ; 

 but perhaps a grouping here, of what may be termed preventive 

 measures, will be of some use. 



It is the grower of orchard fruits that suffers most from borers ; 

 for while some small fruits are subject to this kind of attack, the 

 greatest and most permanent injury is done to trees. Peach-trees 

 are girdled at or near the surface of the ground by a Lepidop- 

 terous borer ; apple, pear, quince, and similar trees are attacked 

 on all parts of the trunk, yet preferably near the base, by Coleop- 

 terous larvae ; and most of our fruit trees are subject to the attacks 

 of bark-beetles. Many of the shade trees suffer in a similar man- 

 ner, and some species attack indiscriminately both orchard and 

 forest growth. It is easier, as a rule, to keep borers out than to 

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

 resort to mechanical measures. The simplest and usually a most 

 effective method is the use of a rather close-meshed wire mos- 

 quito netting on the younger orchard trees. The parents of both 

 the round and flat-headed apple borers are quite large, and 

 unable to lay their eggs through such a netting, provided that it 

 be kept half an inch from the bark at all points. In this way 

 apple and other trees subject to similar injury may be effectively 

 protected, and trees once netted will need little attention, save 

 occasional retying for several years. The netting should be galvan- 

 ized, lacquered, or thoroughly painted, and should have sufficient 

 lap when first put on to allow the tree to make considerable 

 growth. It must be closely tied to the trunk at the top, or the 

 interval must be filled with cotton or a similar material, so that 

 the insects cannot get inside the cage. In like manner, the soil 

 must be hilled around the wire at the base to prevent entrance at 

 that pomt. Should the trees be already infested, such beetles 



