UNITED STATES DEPARTMENT OF AGRICULTURE 



BULLETIN No. 765 



Contribution from the Bureau of Plant Industry 

 WM. A. TAYLOR, Chief 



&J?*%jru 



Washington, D. C. 



April 18, 1919 



STRAINS OF WHITE BURLEY TOBACCO RESISTANT 



TO ROOT-ROT. 



By James Johnson, Agent, and R. H. Milton, Assistant, Office of Tobacco 



Investigations. 



CONTENTS. 



Relation of root-rot to the cropping system in 



practicaltobacco culture 



Description of root-rot 



Cause of the disease 



Varietal resistance and susceptibility 



Page. 



1 

 2 

 5 

 5 



Page. 

 .Development of Burley strains resistant to 



root-rot 7 



Experiments in the White Burley district of 



. Kentucky 8 



Resistant Burley strains recommended for 



sick soils in White Burley districts 10 



RELATION OF ROOT-ROT TO THE CROPPING SYSTEM IN 

 PRACTICAL TOBACCO CULTURE. 



In the systems of tobacco culture prevailing in the United States 

 there are two outstanding extremes in the management of the land. 

 In one case tobacco is grown on the same soil year after year for 

 indefinite periods, while in the other there is a rotation of crops in 

 which only one or two crops of tobacco are grown on the land in a 

 period of 8 to 10 years. The continuous-culture system is character- 

 istic of the cigar-tobacco section of New England and to a con- 

 siderable extent of Wisconsin and Ohio, while on the tobacco lands 

 of Pennsylvania the systematic rotation of crops is the rule. In 

 the southern tobacco-growing sections generally there is consider- 

 able variation in farm practice in this particular, but in most dis- 

 tricts it is seldom that the system of continuous tobacco culture is 

 attempted. The practice of growing only one or two crops of tobacco 

 on the land and then allowing a period of 6 to 10 years to elapse be- 

 fore cropping to tobacco again is especially characteristic of the 

 Burley section of Kentucky and the adjoining States. 



These radically different practices have not developed without 

 good reason on the part of the growers, and the cause is a matter 



96766°— 19— Bull. 765 



