208 AGRICULTURE 



3. Take two potatoes affected with scab. Wash one in the for- 

 malin preparation described in the appendix on page 307. Plant 

 both. What is the difference in the appearance of the crop from 

 each? 



4. Examine plants affected with fungous diseases. What are the 

 most troublesome fungous diseases of your locality? What crops do 

 they attack, and what remedies are used? 



INSECT ENEMIES 



Injuries from Insects. Of all the creatures of the animal world, 

 which inflict most injury on man? You think first of the beasts 

 of the field, fierce lions and man-eating tigers. But man has 

 worse foes than these. You name the serpents, venomous 

 rattlesnakes and deadly cobras. Yet it is not they that inflict 

 most injury on the human race. 



More harm and ruin and death have been caused by insects than 

 by all other creatures of the animal world. Indeed, we are only 

 beginning to realize the extent of their injuries, as, for in- 

 stance, that they convey germs of diseases, such as malaria and 

 yellow fever. 



But though their work as messengers of disease is just being made 

 known, their work as messengers of want and famine is an old 

 story. Since Pharaoh ruled in Egypt, thousands of years ago, 

 history has been recording plagues of insects. They come on foot 

 in hosts such as no human army ever gathered; they come on 

 wings so that the face of the earth is darkened. They find fair 

 fields and bountiful crops and leave behind not one green twig 

 nor blade of grass. 



By skill and labor man has learned to some extent to control 

 them and to prevent their ravages. Yet every year in the United 

 States insects destroy at least one tenth of the agricultural crops. 



