82 DISEASES OF GINSENG. 



ginseng root other than where the last year's leaf stalk had bro- 

 ken off leaving the ends of the numerous conducting tubes expos- 

 ed to contact with the soil. The fungus enters here and works 

 down these tubes until practically all of them are diseased to the 

 extent that the ginseng plant wilts for want of water. 



Whenever wilted plants are observed it is advisable to dig 

 the roots at once and dry them so as to remove the source of in- 

 fection. Sterilizing the soil with steam or formalin might be 

 advisalile when the disease is very destructive. It may be advis- 

 abile to cultivate only resistant roots. Nothing has been done ex- 

 perimentally to substantiate this method of control of this disease. 



Several oliservations made during our studies on this dis- 

 ease seem to indicate that this malady is most destructive in gar- 

 dens mulched with sawdust. Whether there is some real relation 

 existing here or whether it was a mere coincidence is not certain. 

 It is worth consideration, however, and should be more fully in- 

 vestigated. 



Black Rot. 

 (sclerotinia sp.) 

 Roots attacked hy the Black Rot disease are when dug coal 

 black in color. The roots are devoid of all fibers and are covered 

 with many black protuberances or lumps (Fig 33) on the surface. 

 The coal black color of the roots changes to a dirty gray when 

 the roots are dried. This diseased condition is caused by a para- 

 sitic fungus which penetrates and grows in the tissues of the root. 

 It may gain entrance through any part of the root. Some infec- 

 tions were found which had started at the crown, others in small- 

 er roots. The outer tissue of the root is attacked first and com- 

 pletely disorganized, being replaced by a tangled, compact mass 

 of fungus threads. This mycelium then turns black, giving the 



