Journal of Agricultural Research 
Vol. V, No. s 
I84 
Conclusive work on species of Fusarium which produce tuber-rot with 
sufficiently delimited species dates from Appel and Wollenweber’s funda¬ 
mental work on the form genus Fusarium. During the progress of these 
studies Wollenweber established the wound parasitic nature of Fusarium 
coeruleum (Lib.) Sacc. and F. discolor , var. sulphureum (Schlecht.) App. 
and Wollenw., and the causal relation of these species to a definite type 
of rot. Jamieson and Wollenweber in 1912 (5) described an external 
dry-rot caused by F. trichothecioides Wollenw. Wollenweber in 1913 
(19, 20) extended the list of species of Fusarium causing tuber-rot by the 
addition of the following: F. ventricosum App. and Wollenw., 1910, and 
F. rubiginosum App. and Wollenw,, 1910 [considered a synonym of 
F. culmorum W. G. Sm., 1884, by Wollenweber, 1914 (21)]; F. subulatum 
App. and Wollenw., 1910, as a weak wound parasite under special con¬ 
ditions; F. orthoceras App. and Wollenw., 1910, and F. gibbosum App. 
and Wollenw., 1910, as probable causes of tuber-rot. 
Jamieson and Wollenweber’s description (5) of the powdery dry-rot 
caused by F. trichothecioides is the first description of a definite rot con¬ 
clusively demonstrated to be caused by a species of Fusarium which is 
sufficiently described in its normal 1 stages to insure certain identifica¬ 
tion. However, Wilcox, Link, and Pool (17) published a description 
one year later of the same disease and subnormal stages of the same 
organism, for which they proposed a new name—i. e., F. tuberivorum 
Wilcox and Link. The examination of material similar to that used by 
Wilcox and Link from Alliance, Nebr., demonstrated that F, tuberivorum 
is identical with F. trichothecioides . 
The increasing number of rotting tubers submitted to the Department 
indicated the existence of several types of a rot not hitherto described 
which were caused by species of Fusarium and focused the author’s 
attention during the past year on a laboratory study of these diseases. 
The object of this paper is to demonstrate the parasitic nature of certain 
species of Fusarium and to contrast these organisms and the resulting 
types of deterioration with those already recognized. The economic 
importance of these rots and the interest manifested by pathologists in 
a general group of diseases caused by species of Fusarium suggested the 
advisability of a comprehensive treatment of the species known to cause 
decay as an aid to their diagnoses and ultimate control. 
The tuber-rots considered in this investigation are all of the stem-end 
and wound-parasitic type. They are not sharply differentiated from 
each other nor from those previously described as caused by the following 
species: F. coeruleum; F. discolor , var. sulphureum; F. trichothecioides, 
After having made isolations from several hundred submitted specimens 
of stem-end-diseased tubers and from many more rotting as the result 
of wound and lenticel invasion or inoculation with known species, the 
1 For a discussion of the idea '‘normal’' as used in this paper, see Wollenweber (21, p. 255-257). 
