Insects in General 

 CLASSIFICATION 



The insects that injure agricultural crops can be roughly grouped 

 into two classes : those that feed upon the roots and underground parts of 

 plants, or "root feeders;" and those that feed upon the leaves and other 

 parts of plants above the ground, or "leaf feeders." 



Each of these groups can in turn be divided into two other classes : 

 insects which bite their food, or "biting insects," and those which suck 

 their food, or "sucking insects." 



Both classifications are most important from the viewpoint of insect 



control. 



The mouth parts of the biting insects consist of an upper and lower 

 lip between which are two pairs of jaws with which portions of the food 

 plant are bitten out and masticated. Attached to these jaws are slender, 

 jointed organs used in guiding the food to the mouth or as sense organs. 



The mouth parts of sucking insects are modified into a long, jointed 

 tube or beak and several hair-like bristles which are enclosed within it. In 

 feeding, the beak is placed against the surface of the plant while the 

 bristles or piercing organs are forced into the tissue. The plant juice is 

 then sucked up through them by a pumping motion of the mouth. 



METHODS OF CONTROL 



There are two general methods of insect control, the cultural or 

 natural method, and the artificial method. 



The natural method consists of handling the soil or the crop in 

 such a way as to prevent or reduce insect injury, and in fighting injurious 

 insects with their natural enemies. 



The artificial method consists of the application of any substance 

 to a crop for the purpose of killing attacking insects or making the plants 

 so distasteful to them that they will not feed upon them. 



Natural Methods of Control 



Application of the natural methods of control depends largely upon 

 the habits and life history of the insect to be controlled. For example, 

 in the case of the grasshopper we know that its egg stage is passed in the 

 ground during the fall and winter. Fall plowing, harrowing and discing 

 will kill the grasshopper in the egg stage. 



Crop Rotation 



Crop rotation is one of the principal factors in insect control. Many 

 insects feed upon only one crop or those closely related botanically. 

 It is evident, therefore, that if the same crop is planted on a field for 

 several years in succession the insects attacking it are likely to accumu- 

 late in and about it until serious damage results. The length of rotation 

 necessary to insure against injury by an insect or other crop pest, depends 

 upon the pest in question. For example, the corn root worm can be con- 

 trolled by alternating corn with any other crop ; while white grubs and 

 wireworms require a three or four year rotation; and the sugar beet 

 nematode a much longer rotation. 



Other insects deposit their eggs upon certain crops or in the soil 

 where these crops are growing or have grown. Loss can be avoided by 

 following such crops with others which are not attacked by this class 

 of insect. 



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