30 INSECT PESTS OF FARM, GARDEN AND ORCHARD 



which any given procedure will have upon the injurious insects with 

 which they may have to contend. A field which has for several 

 years been in wheat, corn,, or tobacco, may be sown with some 

 other crop for the sake of soil improvement, but how often is it 

 considered necessary to rotate crops to avoid insect pests? In 

 most cases they are left out of consideration until a crop has been 

 seriously injured and the necessity for a change of methods thus 

 impressed on the owner. 



Particularly while crops are young they should be frequently 

 inspected and examined for any evidence of the pests which com- 

 monly affect them. Be prepared to attack any pests which 

 may be found upon their first appearance, for many of the 

 most destructive insects increase with amazing rapidity, and 

 when they have become abundant it is too late to prevent the 

 damage. 



Crop Rotation. One of the most important factors in insect 

 control is the rotation of crops in such a manner that the same 

 crop shall not be grown continuously on the land. In many 

 cases a yearly rotation will be advantageous, while a frequent 

 rotation will always be found beneficial. Many insects feed on 

 one crop only. It is evident, therefore, that if they hibernate in 

 or near the field which it occupied and it is then planted to the 

 same crop the next year, they will be furnished food for their 

 increase, while if the field be planted in a crop not attacked by 

 the insects peculiar to the previous crop they will have to migrate 

 from it, with probably a very considerable mortality as a conse- 

 quence, for they will radiate in all directions and many will die 

 before finding food, while many more will have been destroyed 

 in the preparation of the old field for the new crop. 



The western corn root-worm may be entirely controlled by a 

 rotation so that corn is never grown two successive years on the 

 same land, for the larvae feed only on the roots of corn, and when 

 it is followed by a small grain, grass, or clover, they are starved 

 out. Injury by the Hessian fly to wheat is also very materially 

 reduced where a frequent rotation is practised, as is that of the 

 chinch-bug on corn. 



Care should be exercised to arrange a rotation in which crops 

 nearly related botanically do not follow each other, for usually 

 the same insects attack them. Thus white grubs, cutworms, 



