6 The Bulletin, 



protection that can be secured from them. The most that we can pre- 

 tend to do here is to present the general facts, with such recommenda- 

 tions for control as seem, from present even incomplete evidence, to 

 offer the best hope of relief. The illustrations are the same as in the 



previous Bulletin. 



GENERAL CONSIDERATIONS. 



In dealing with insect pests on corn, it must be constantly remem- 

 bered that the crop is of relatively low commercial value, the margin 

 of actual profit is small, hence expensive measures are not justifiable 

 except in limited areas where their use will prevent the insects from 

 spreading over larger areas. It may not be profitable to spray a whole 

 cornfield to kill insects, yet the spraying of a few rows or a certain por- 

 tion of the field may be profitable if by that means the pest can be pre- 

 vented from spreading farther. The small margin of profit on the crop 

 as a whole renders it difficult or impossible to combat some of the pests 

 satisfactorily. 



Again, corn is grown on such large areas and there are so many indi- 

 vidual plants in a field that the treatment of each individual plant is 

 usually out of the question. 



Therefore, in combatting many of the insect pests of corn we must 

 rely on such methods of culture and handling of the crop as shall ren- 

 der it least liable to injury ; in other words, the treatment must be pre- 

 ventive rather than curative — and this frequently necessitates taking 

 the insects into account before the crop is planted, even in the very 

 selection of the lands where it is to be planted, or, in severe cases, even 

 modifying the manner of rotation of the crops which shall precede the 

 corn. How far one is justified in going in recasting the plan of his 

 farm operations to protect his corn from injury will of course depend 

 upon how severe the injury is, and upon the value which he places upon 

 the corn crop itself. 



CULTURAL CONSIDERATIONS. 



By changing or modifying the methods of culture much may be done 

 to avoid insect injury. This is so important that we will consider it in 

 more detail. 



Rotation. — Any system by which corn follows grass or a growth of 

 weeds is injurious, from the standpoint of insect pests. Where land 

 just from sod is put in corn, the crop suffers more from wire-worms, 

 Avhite grubs, root web-worms and cut-worms than it does when it follows 

 a cultivated crop like cotton. Suppose we have a field now in sod which 

 we wish to bring into cultivation : A system of rotation which will give 

 the minimum amount of insect injury to the corn might be arranged as 

 follows : First year, plant the field in a small grain, and after that in 

 peas. Second year, cotton, potatoes, cabbage or other cultivated crops. 



