DISEASES OF PLANTS. 245 



lings by treatment of the soil with formaldehyde, and the ginseng nematode and 

 its relation to golden seal. 



The blaclj rot fungus is said to attack the roots during the winter and not to 

 spread at all during the growing season. During the first winter only the 

 outer part of the diseased root is blackened, but during the second winter 

 infected roots turn black throughout and become more or less hollow and 

 shrunken. Sterilization of the soil with a 40 per cent solution of formalde- 

 hyde, 1 part to 50 or 1 part to 25, applied at the rate of 1 gal. per square foot, 

 has successfully controlled the black rot fungus. Sterilization with steam, 

 where such was possible, has also given good results. 



For the control of the damping-olf of seedlings, soil sterilization by applica- 

 tion of a solution of formaldehyde is recommended. 



A detailed account is given of studies conducted to determine whether golden 

 seal could be used in rotation with ginseng where nematodes were present in 

 the soil, a preliminary account of which has already been given (E. S. R., 31, 

 p. 345). For the control of the nematodes, no chemical treatment has been found 

 entirely satisfactory, and the only practical method seems to be that of steam 

 sterilization, which, it is said, would cost about $10 per 1,000 square feet of soil. 



Experiments on the control of the root-knot nematode, J. A. McClintock 

 {Michigan Sta. Tech. Bui. 20 {1915), pp. 3-23).— The results of field and lab- 

 oratory experiments for the control of nematodes are given, the investigation 

 being carried on in connection with a study of ginseng diseases (see above). 



In the field plats were enclosed by galvanized sheet iron to a depth of 

 30 in. and treated with carbon bisulphid, tobacco stems, sulphuric acid, formalde- 

 hyde solutions, naphthalin, ammonia, Black Leaf 40, tobacco dust, kerosene, 

 and gasoline. The data obtained from the above experiments indicate that 

 none of the treatments could be depended upon to eradicate the root-knot 

 nematode from the soil. Carbon bisulphid, tobacco stems, and strong formalde- 

 hyde solutions reduced the number of nematodes, and these treatments might 

 be practicable in case of rapidly growing crops, but they would not be of any 

 pai'ticular importance with a crop lilce ginseng, which occupies the soil from 

 four to sis years. 



The laboratory experiments were carried out on egg masses treated with 

 a large number of different chemicals. Taken as a whole, it did not appear 

 that the chemicals could be depended upon to control nematodes as they did 

 not prevent the hatching of the eggs. 



Steam sterilization under pressure of 70 lbs. for 30 minutes or 80 lbs. for 15 

 minutes, it is thought, would destroy all the nematodes present in soil. 



Altemaria panax, th.e cause of a root rot of ginseng, J. Rosenbaxtm and 

 C. L. ZiNNSMEiSTEE {U. S. Dcpt. Agi'., Jour. Agr. Research, 5 {1915), No. 4, pp. 

 181, 182, pis. 2). — While engaged in a study of the diseases of ginseng, the 

 authors noted in a garden near Cleveland, Ohio, roots which showed a peculiar 

 dry-rotted condition about the crown. An examination showed the presence 

 of an Alternaria-like fungus, closely resembling that described by Whetzel as 

 the cause of blight, to which the name A. panax was given (E. S. R., 27, p. 446). 



By means of culture and inoculation experiments the authors have produced 

 the disease in which symptoms and lesions were characteristic when made from 

 both A. panax and the species thought to resemble it. As no cultural differ- 

 ences can be recognized, they believe the two fungi are identical and that the 

 organism causing the blight may also cause the root rot. 



For control, in addition to spraying, care in ti'ansplanting so as to injure the 

 roots as little as possible, the removal of all tops and stems in the fall, and, 

 where the crowns of the roots are sufiiciently deep below the surface, burning 

 over the soil after the tops have been removed are recommended. 



