CHAPTER V 

 THE DISEASES OF PLANTS 



* SECTION XXV THE CAUSE AND NATURE OF 

 PLANT DISEASE 



Plants have diseases just as animals do; not the same 

 diseases, to be sure, but just as serious for the plant. 

 Some of them are so dangerous that they kill the plant ; 

 others partly or wholly destroy its usefulness or its beauty. 

 Some diseases are found oftenest on very young plants, 

 others prey on the middle-aged tree, while still others 

 attack merely the fruit. Whenever a farmer or fruit 

 grower has disease among his plants, he of course loses 

 much profit. 



You have all seen rotten fruit. This is diseased fruit. 

 Fruit rot is a plant disease. Fruit rot costs farmers mil- 

 lions of dollars annually. One fruit grower lost sixty car 

 loads of peaches in one year through rot which could have 

 been largely prevented if he had known how". 



Many of the yellowish or discolored spots on leaves are 

 the result of disease, as is also the smut of wheat, corn, and 

 oats, the blight of the pear, and the wilt of cotton. Many 

 of these diseases are contagious, or, as we often hear said of 

 measles, " catching." This is true, among others, of the 

 apple and peach rot. A healthy apple can " catch " this 

 disease from a sick apple. You often see evidence of 



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