Pethybeidgk and Laffeety — Dry-Rot of the Potato Tuber. 1 97 



disease, but not tuber-rot, of Solanum tuberosum in the United States of 

 America, possibly also in Southern Europe, and the potato districts of South 

 Africa, Australia, &c." 



Quite a different type of dry-rot was described by Jamieson and 

 Wollenweber in America 1 about four years ago, which, in its general aspects, 

 much more closely resembles the common dry-rot of potato tubers in our 

 own country, although it differs from the latter in some respects, as will be 

 shown later (see p. 218). These authors state that this new form of dry- 

 rot is clearly to be distinguished from the wilt and dry-rot ascribed by 

 Smith and Swingle to F. oxysporum ; and, presumably to emphasize this 

 distinction, they refer to the new form as an external dry-rot. The cause of it 

 was determined to be a new species of Fusarium to which the name 

 F. trichothecioides was given. It is stated that tubers could be infected with 

 the disease by merely rubbing their surfaces with a platinum loop bearing 

 the fungus, although more certain results were obtained when the inoculation 

 was made through an actual wound. 



It is important to know whether this species not only rots tubers, but 

 also causes a wilt of the plant, as F. oxysporum does. Apparently Jamieson 

 and "Wollenweber believe that it does cause a wilt, although they do not seem 

 to be absolutely confident in the results of their experiments, for they do not 

 include this important point in the summary which they give of their work. 



What at first sight, at any rate, would appear to be yet another American 

 type of dry-rot of the potato tuber was described in 1913 by Wilcox, Link, 

 and Pool. 2 



Although in a general way this rot appears to be similar to the external 

 dry-rot described by Jamieson and Wollenweber, yet the organism causing it 

 was considered by the three authors to be a new one, and they named it 

 Fusarium tuberivorum. They distinctly state that the fungus is incapable of 

 infecting any part of the potato plant other than the tuber, hence it is not a 

 wilt-producing parasite, and in this respect, therefore, it must be regarded 

 as clearly differing from F. trichothecioides, if Jamieson and Wollenweber's 

 views on this matter are correct. 



Soon after the publication of Wilcox, Link, and Poole's description of 

 F. tuberivorum, Wollenweber 3 stated that he, in common with Orton and 



1 Jamieson, C. O., and H. W. Wollenweber. An external Dry-Rot of Potato Tubers 

 caused by Fusarium trichothecioides Woll. Washington, Academy of Science ii. No. 6, 

 1912, p. 146. 



2 Wilcox, E. M., Link, G. K. K., and V. W. Pool. A Dry-Rot of the Irish Potato 

 Tuber. Research Bull. No. 1. Nebraska Agric. Expt. Station, 1913. 



3 Wollenweber, H. W. Ramularia, Mycosphaerella, Necfcria, Calonectria, usw. 

 Phytopathology, vol. iii. No. 4. 1913, p. 206. 



