B. p. I.— 373. 



THE FIELD TREATMENT OF TOBACCO 

 ROOT-ROT. 



NATURE OF ROOT-ROT. 



During the past few years a disease known as root-rot has made 

 its appearance in the tobacco fields in some districts of Kentucky, 

 Connecticut, Ohio, and Wisconsin. This disease is now generally 

 recognized to be due to a soil fungus" {TJiielavia hasicola), which 

 attacks the feeding roots of the tobacco as fast as they are thrown 

 out. The root-rot generally makes its first appearance in the field 

 in spots, particularly low spots, and may later develop throughout 

 the field. The most striking feature is the failure of the plants to 

 make a proper growth. The diseased plants are often only 8 or 10 

 inches high when healthy plants set at the same time are ready to be 

 cut. These small plants will be found to have only a small ball of 

 stubby roots, and the fungus can be seen on the blackened or brownish 

 ends of the roots, which in the active stages of the disease have a 

 rotted appearance. 



Root-rot has already been successfully checked in the seed-bed by 

 Selby^ with the use of formalin, and b}^ Shamel^ through sterilization 

 by steam. Nether of these methods can be considered practicable 

 for treating the disease in the field. In experiments made last year 

 by W. W. Gilbert and the writer, a formalin solution applied to 

 a one-tenth acre plot of diseased land at the rate of 500 pounds of 

 formalin per acre"^ gave somewhat increased yields, but not suffi- 

 cient to justify the expense involved. 



FIELD TREATMENT OF ROOT-ROT. 



The object of this circular is to give briefly the preliminary results 

 of the writer's efforts to overcome the attacks of this fungus on the 

 tobacco in the field by the proper use of fertilizers, with the hope 



«See papers by Selby, of the Ohio Agricultural Experiment Station, and by 

 Clinton, of the Connecticut Agricultural Experiment Station. Mr. W. W. Gilbert, of 

 the Department of Agriculture, has a bulletin on this subject in preparation. 

 . ^ Circular No. 59, Ohio Agricultural Experiment Station. 

 c Bulletin No. 91, Bureau of Plant Industry, Department of Agriculture, 1936. 

 ^This would represent a cost of about |60 per acre for the formalin alone, besides 

 the labor. 



[Circ. 7.] 5 



