162 ELEMENTS OF FARM PRACTICE 



3. If five hours of time are required to select and treat enough 

 seed potatoes for an acre, and 30c. worth of material is required for 

 the treatment, what will the total cost of treatment be, tf one's time 

 is worth 15c. per hour? 



INSECTS AND THEIR CONTROL 



Loss to farm crops caused by insects represents a very 

 heavy tax, and increases greatly the cost of producing crops. 

 Many injurious insects, in fact most of them, are always 

 present, and there seems to be little prospect of ever getting 

 rid of them. The problem of the farmer is to know the 

 habits and methods of control of the insects affecting his 

 crops, and to wage continuous war against them. 



Habits. — Insects have certain characteristics that dis- 

 tinguish them from other animals. There are three distinct 

 sections to their bodies: head, trunk and abdomen. They 

 also change in character as they develop. There are four 

 quite distinct changes: first, the egg stage; second, the 

 larval or worm stage, — this is the stage at which they do 

 most of the damage to crops; third, the pupal or resting 

 stage, during which time the insect changes to the fourth 

 stage, that of the mature insect. 



Two Classes. — Insects may be divided into two classes 

 by their methods of eating. Some insects chew their food. 

 The^e insects can be poisoned by spraying poison on the 

 plants they are eating. Other insects force their sharp 

 mouth parts into the skin or bark of the plant and suck out 

 the juices. Poison sprayed on plants will not affect these 

 insects, because they do not get it. They must be killed 

 by spraying with something that will kill them simply by 

 coming in contact with their bodies, such as soap solution 

 or tobacco extracts. Among the most common biting insects 

 that can be poisoned are potato bugs, cutworms, army worms, 

 currant worms, cabbage worms, grasshoppers, plum curculio, 

 and codling moth. The most common sucking insects are 

 plant lice, squash bugs, chinch bugs, and scale insects. 



Remedies. — There are several ways of combating in- 

 sects, the most generally effective way being good farming; 

 that is, the rotation of crops, fall plowing, clean fence 

 corners, keeping all rubbish picked up about the fields, 

 and maintaining about the place a good grove or other 



