UNITED STATES DEPARTMENT OF AGRICULTURE 



In Cooperation with the 



College of Agriculture, University of Wisconsin 



DEPARTMENT BULLETIN No. 1256 



Washington, D. C. 



October 13, 1924 



TOBACCO DISEASES AND THEIR CONTROL. 



By James Johnson, Agent, Office of Tobacco Investigations, Bureau of Plant 

 Industry, and Professor of Horticulture, College of Agriculture, University 

 of Wisconsin. 



CONTENTS. 



Page. 



Introduction 1 



The nature of plant diseases 3 



Losses from disease 3 



The plant bed as a source of infec- 

 tion 4 



Plant-bed sanitation 4 



The sterilization of soil for plant 



beds 5 



Stem or stalk diseases 7 



Page. 



Root diseases i§ 



Leaf diseases 25 



Injuries due to physical agencies 41 



Unimportant or rare diseases not 



otherwise classified 41 



Damage in curing and fermentation- 43 

 Diseases of tobacco in foreign coun- 

 tries 48 



Bibliography _* 50 



INTRODUCTION. 



The tobacco plant has been cultivated in the United States for 

 more than 300 years. Nearly 1,750,000 acres of land are devoted to the 

 production of the crop, which is now approximately one and one-third 

 billion pounds per year. W nile new areas have been gradually 

 opened to the culture of the crop, the growing districts have re- 

 mained remarkably constant in location, so that most tobacco soils 

 are subject to continuous or repeated intensive culture, naturally re- 

 sulting in an accumulation of diseases and insects which affect this 

 crop in particular. The production of a good yield and high quality 

 of tobacco up to the manufacturing stage has become increasingly 

 difficult, in spite of the greatly increased knowledge and experience 

 on the part of the growers concerning the various aspects of the cul- 

 ture of the crop. Some of the most important and obscure difficul- 

 ties confronting the growers are those which belong to the class of 

 plant diseases. It is the purpose of this bulletin to describe these 

 diseases, giving the causes where known, and to suggest the best 

 means of control available. 



The tobacco-growing districts are relatively small areas, located 

 largely east of the Mississippi River, but ranging from the warmest 

 to almost the coolest climate in the United States (fig. 1) . These dis- 

 tricts, furthermore, produce distinct types of tobacco, used for va- 

 rious purposes, as a result of employing different varieties of seed. 



91061°— 24 1 



