GENERAL FAini METHODS AGAINST INSECT PESTS. 29 



these insects iu the grass land be at once concentrated 

 upon the comparatively few corn plants, the injury will be 

 much more severe than if the change be a gradual one, 

 with first a crop not of the grass family which would be 

 largely immune from their attacks, and then a small grain. 

 The value of rotation is possibly best illustrated in the case 

 of the Western Corn Eoot-worm, which is never injurious 

 to corn after the land has been in a small grain or clover. 

 The Hessian Fly, Wheat Isosoma, Wheat Plant-louse, 

 Wireworms, and many other of our worst pests may be 

 largely controlled by a rapid rotation, and their increase 

 and consequent depredations are very often due almost 

 entirely to a lack of such practice, which is also of the 

 utmost importance in preventing soil depletion. 



Thus a proper understanding of the pests with which 

 he has to deal and a timely consideration and application 

 of these homely methods may be of the greatest value, 

 and indeed often the only available means for the control 

 of the larger part of the insect enemies of the general 

 farmer. 



