CHAPTER 20 



INSECT PESTS AND THEIR CONTROL 



BY W. B. WOOD 



Scientific Assistant, Bureau of Entomology, U. S. Department of Agriculture 



Insects are, without doubt, the greatest enemies of the farmer, for they 

 destroy the crops of field and garden and render the fruit on the trees unfit 

 for use; they injure the domestic animals by constant irritation, causing 

 them to lose weight and even to die. Stored grains, tobacco and other 

 farm products also suffer from their attacks. 



After studying their life histories and habits, methods of control have 

 been devised by which they can be combated with a reasonable amount of 

 success. Many species can be held in absolute control by thorough and 

 timely applications of the proper remedies, while others are only partially 

 held in check. 



In order to intelligently apply a treatment for the control of an insect, 

 something of its habits must be known, especially in regard to its manner 

 of feeding. Most of the important pests fall within two great groups, 

 namely, biting or chewing insects and sucking insects, depending on 

 whether the mouth parts are chisel or pincher-like in the first class, or 

 beak-like and made for piercing and sucking in the second class. A 

 number of these pests will fall in certain special groups which require a 

 definite treatment, indicated by their manner of living or by the injury they 

 do. Some of these special classes are internal feeders, as boring insects, 

 subterranean insects and insects affecting stored products. 



The external feeders, which have biting mouth parts, usually feed upon 

 plants by gnawing out small pieces of the plant tissue which are swallowed. 

 This group includes the larvae or caterpillars of moths and butterflies, the 

 larvae of beetles and the adults, grasshoppers and crickets, and the larvae of 

 some species of Hymenoptera or the wasp group. Such insects may usually 

 be controlled by applying a poison to the plant, either as a fine spray or as 

 a powder dusted or blown over its surface. The arsenicals have been found 

 to be the best remedy for this group. 



The sucking insects feed by piercing the skin or epidermis of plants 

 with their sharp beaks and sucking the sap. This group of insects is 

 represented by the tree bugs or Hemiptera, to which order belong the 

 squash bug, scale insects, plant lice and leaf hoppers. It is evident that a 

 stomach poison on the surface of the plant would not affect insects of this 

 class, so it is necessary to use what is known as a contact insecticide, which 

 should be applied as a spray or wash directly to the insect's body. Such 



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