CROP ENEMIES AND FRIENDS 



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By deep fall plowing many insects are destroyed. Cutworms 

 are brought to the surface and are frozen in winter ; grasshopper 

 eggs are buried so deep that the insects cannot come out. 



Fertilizers give plants vigor to resist injury from insects, espe- 

 cially from root-feeding ones. 



Insects collect on a trap crop which is planted early or at intervals 

 in another crop. They can be destroyed before they attack the 

 main crop. 



The time of planting and cultivation can sometimes be planned 

 so as to check insect enemies. Late-sowed wheat suffers least 

 from the Hessian fly, early- maturing cotton largely escapes the 

 boll weevil, late-planted corn is least injured by cutworms. 



Other things being equal, two crops having the same troublesome 

 insect enemies should not be placed side by side. Corn beside 

 grass is more liable to cutworms; beside wheat, to chinch bugs. 



Rotation of crops is an important means of protection against 

 insect injury. In the case of many insects, it is the only practicable 

 remedy. If land be planted in the same crop year after year, the 

 soil becomes infested with insects injurious to it. 



Insecticides. The kind of poison used depends on the struc- 

 ture and feeding habits of the insect. As to feeding habits, insects 

 may be divided into two classes, chewing and sucking ones; the 

 first have mouths arranged for chewing food, the second have 

 mouth-tubes which they insert into a plant or animal and through 

 which they suck its juices. 



Chewing Insects. Chewing insects usually live on the foliage 

 of plants. They can be killed by applying to their food plants a 

 poison, generally some form of arsenic. One of the cheapest and 

 best forms is Paris green. The acid in it, like that in copper sul- 

 phate, needs to be counteracted by an alkali, and so with it also 

 lime is used. Properly prepared and applied, Paris green is 



