96 DISEASES OF GINSENG. 



The tax upon the plant's resources the previous season has left it 

 in poor condition to build a new absorbing system of fibers. 

 They are soon attacked by the parasite which has wintered in the 

 soil or rotted rootlets and the root, exhausted of food and depriv- 

 ed of its water supply, cannot maintain the newly expanded top, 

 which promptly wilts and the plant dies, or at best the top makes 

 a poor gTowth (Fig. 43), matures early, and the root at the end of 

 the second season, if not entirely rotted, is at least no larger than 

 in the autumn of the season before. In short, the plant becomes 

 stunted and root-growth does not proceed. 



II. Control. The suggestions which have been made for 

 the control of the disease were based entirely upon the work done 

 by Briggs C08) of the Bureau of Plant Industry, U. S. D. A., on 

 the control of the same disease of tobacco. He showed that the 

 fungus (Thelavia hasicola) is very sensitive to acid, i. e., will 

 not grow in acid media or acid soils. While the acidity of the 

 soil does not destroy the fungus, it is nevertheless unable to attack 

 the roots of tobacco seedlings in such soil- However, if this soil 

 were made alkaline the parasite would at once become active, 

 attack and destroy the roots of the tobacco- After careful quan- 

 titative tests, he treated the land on which tobacco was to be 

 grown with acid phosphate (treated rock) at the rate of 1,000 

 pounds to the acre, with good results, in preventing loss from the 

 parasite. 



Our examination of the gardens of the State during 1909 

 showed that many, perhaps the majority of the growers had been 

 applying lime more or less abundantly to their ginseng beds. In 

 every case it seemed evident that this had increased the injury 

 from "fiber rot''. Wherever unlimed beds were handy for com- 

 parison it was evident that they suffered less from the disease. 



