CONTROL OF PLANT DISEASES 



471 



Fig. 3. Labgb Chestnut Tbees killed bt the Babk Disease. 



wave of disease. It to-day causes loss estimated at $36,000,000 annually 

 in the United States. New York alone has incurred a loss of $10,000,- 

 000 in one year. 



The asparagus rust prohibited successful asparagus culture in sev- 

 eral states and threatened that industry in California, where the 

 crop occupies yearly over 7,000 acres of land, until means of control 

 were devised bv scientific men. The rice smut was recognized in its 



Fig. 4. Map showing the DisxniBUTioN of the Chestndt Bark Disease. 

 Black shows area of severe Infection ; round dots, presence of disease prior to 1909 ; 

 + indicates tlie spread of the disease during 1909. After Metcalf. 



