6 BT7LLETIX 765, U. S. DEPARTMENT OF AGBICEXTT/BE. 



several years and which is not " tobacco sick." the Burley tobacco 

 will produce as great or a greater weight, plant for plant or acre for 

 acre, than the Connecticut Havana. If we pull up and examine the 

 roots of plants of both varieties grown on healthy ground, they are 

 found to be large and white. On sick soil, however, a Burley plant will 

 usually have only relatively few stubby black roots, as compared with 

 the Havana tobacco, although the latter variety also may show some 

 signs of the disease. The difference in yields between two varie- 

 ties can be made even more striking, since we have varieties two 

 and three times as resistant as the Connecticut Havana. Xo 

 variety more susceptible than the ordinary TVhite Burley strains 

 grown in the Burley section lias been found. Such a test can be made 

 easily on any soil, and in connection with this study it has been re- 

 peated a great many times, with the expected results in nearly every 

 instance. TYnere the expectations were not realized there has been 

 good reason for suspecting disturbing factors other than the Thie- 

 lavia root-rot. 



The behavior of resistant and susceptible varieties on sick soils is 

 regarded as positive proof of the extent of the injury attributed to 

 the root-rot. It can be satisfactorily explained in no other way. The 

 accumulation of data upon the subject over a period of five years in 

 Wisconsin. Connecticut. Kentucky, and in Canada, together with 

 field surveys in other States, has left no doubt of the widespread 

 occurrence and economic importance of the disease, 



TTith the marked differences in resistance to the root-rot mani- 

 fested by different varieties of tobacco clearly in mind, it will be 

 readily seen that these differences satisfactorily account for the 

 marked contrast in methods of handling tobacco lands in some of the 

 northern cigar-tobacco districts and in the Burley district. The ex- 

 treme susceptibility of the Burley variety permits of no other system 

 than a short cropping period for tobacco and a long " rest " for the 

 land. In the northern cigar-tobacco districts tobacco culture has in- 

 volved a struggle between old sick soils and the resistance of the 

 varieties grown. The influence of this struggle upon agriciiltiiral 

 practice has been threefold. First, the growers have applied enor- 

 mous quantities of fertilizers, hoping thereby to remedy the worn-out 

 condition of the soils, which has resulted in more or less wastage of 

 fertility, since sick soils can not be benefited appreciably by ferti- 

 lizers except under special conditions (by the use of resistant types, 

 through prevailing high soil temperatures, etc.) . In the second place, 

 resistant strains apparently have been unknowingly selected and de- 

 veloped on account of their adaptability to these soils. In the third 

 place, the disease in many instances has made such progress that 

 growers have been compelled to change to new soils frequently, and 



