144 



PLANT DISEASES 



them into several groups. These diseases are especially severe 

 on fleshy fruits, such as apples, pears, peaches, plums, cherries, 

 tomatoes and many other plants. Many of these diseases can 

 be held in check by the proper spray treatment. 



The diseases of the grain crops are very destructive and are 

 the causes of heavy losses. The most conspicuous and most im- 



portant of these diseases are the rusts and smuts (Fig. 91) which 

 are fungous growths in and on the plants. But there are many 

 other less prominent diseases of the grain plants which are 

 very destructive. 



The study of plant diseases is a study in itself, a well-defined 

 branch of botany known as Plant Pathology. Most of the Agri- 

 cultural Experiment Stations, of which there is at least one in 

 each state, employ one or more plant pathologists who should be 

 consulted by the growers of crops. 



