Nov. IS, igis Sclerotinia Spp. on Ginseng 295 



PATHOGENICITY 



In the spring of 191 2 the writer received a number of black-rotted roots 

 from Wisconsin showing various stages of development of the disease. 

 Isolations were made from these roots by making plantings from the 

 inner tissues of the roots on poured plates of hard potato agar. The 

 fungus was obtained in pure culture, where it produces a characteristic 

 black growth. 



Inoculations on healthy roots made at various times during the summer 

 gave negative results, as would be expected from the nature of the fungus, 

 since the disease always develops in beds during the winter. In October 

 of the same year (191 2) six roots were washed clean and inoculated by 

 placing a piece of the agar pure culture in a small cut made in the tissues 

 of the root. Three similar roots were injured and used as checks. All 

 the roots were planted in soil which had never grown a crop of ginseng. 

 The following March an examination of the roots showed the character- 

 istic symptoms of the disease. Some were entirely black, while others 

 were only partly blackened. The fungus was easily reisolated from these 

 roots. Plate XXIX, figure i, shows two inoculated roots, together with 

 a check root. One of the inoculated roots is entirely black, while the 

 second shows this black color only in part. 



In October, 191 3, inoculations were agam made on ginseng roots. 

 These roots were not injured, but the fungus was placed on the old stem 

 scar. The next March the roots were black, as in the previous year. 

 Reisolations were again made, and the fungus which was obtained pro- 

 duced the characteristic black growth. 



IDENTITY OF THE SPECIES 



The growth of the fungus in culture and the general behavior of this 

 organism differed so greatly from the known species of Sclerotinia that 

 it has always been an interesting question as to the source of the fungus 

 which appeared in isolated gardens throughout the countr>\ One plau- 

 sible explanation is that the fungus, being associated with wild ginseng 

 roots or with one of the common weeds, was brought in from the woods, 

 as many growers make a practice of using leaf mold in preparing their 

 beds. Since the fungus from the description resembled Sclerotinia 

 smilacina Durand, it seemed advisable to determine whether the species of 

 Sclerotinia on ginseng could produce a black-rot of the rhizome of 

 Smilacina spp. and whether the two were also identical in other respects. 



Inoculations on species of Smieacina. — In October, 1913, six 

 rhizomes of Smilacina racemosa were inoculated with a pure culture of 

 the black-rot fungus obtained from ginseng. The inoculations were made 

 by slightly injuring the rhizome and inserting the myceUum of the fungus 

 in the cut. Check plants were also injured. When examined the follow- 

 ing March, the rhizomes showed the characteristic symptoms of black-rot 



