DISEASES OF CULTIVATED PLANTS 621 



known as oxidizing ferments and named oxidase and peroxidase. 

 Both these investigators were able to transmit the disease by inocu- 

 lation of fluid from diseased plants into tho young portions of 

 healthy plants. The difference between the results of the one and 

 the other is in the specific designation by Woods of the oxidizing 

 enzym as the active agent in producing the disease. 



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 

 (Thielavia basicola) , 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 j bed 

 by Selby with the use of formalin, and by Shamel through steriliza- 

 tion by steam. Neither of these methods can be considered prac- 

 ticable for treating the disease in the field. (B. P. I. Cir. 7.) 



The object of this circular is to give briefly the preliminary 

 results to overcome the attacks of this fungus on the tobacco in the 

 field by the proper use of fertilizers, with the hope that the sug- 

 gestions offered can be utilized this season by tobacco growers who 

 have fields affected with this disease. The results of the writer's 

 investigations thus far indicate that the tobacco is much more 

 severely injured by the fungus on fields where the soil has been 

 made alkaline by the long-continued use of large amounts of lime, 

 ashes, and fertilizers containing carbonate of potash. The remedy 

 for diseased soils appears, then, to consist in avoiding the use of 

 lime and in applying the necessary potash in the form of the sul- 

 phate of potash, which is a neutral salt ; and, if the field is badly dis- 

 eased, in applying the phosphoric acid in the form of acid phos- 

 phate in order to heJp neutralize the alkalinity of the soil. The 

 above view as to the cause of the development of the disease in 

 some of the tobacco fields of Connecticut is in harmony with field 

 observations, as will appear in the following pages. 



The Granville Tobacco Wilt. The first indication of the dis- 

 ease is given through the leaves which droop, becoming soft and 

 flabby as though suffering from want of water. This symptom is not 

 accompanied by any change in color; the leaves remaining green 

 for some time after the wilt appears. As a rule tho lower leaves 

 droop first, the wilting gradually proceeding from the ground up- 

 ward. Frequently the leaves on one side of the plant succumb 

 earlier than those on the other side. Some growers believe that one 

 side of the plant may occasionally survive to maturity, though the 



