844 
Journal of Agricultural Research 
Vol. XXI, No. II 
occasionally been isolated in pure cultures from discolored stem tissues 
of wilted plants suggests that it may occasionally cause a wilt of potato 
plants. It has been secured most frequently from tubers which were 
perfectly sound except for the presence of discoloration in the stem-end 
vascular region. For instance, 82.4 per cent of the tubers which gave 
this organism in cultures were browned or yellowed in this region (Table I) 
and were not in any way affected by rot. Only 8.3 per cent of the tubers 
which gave this fungus in culture were affected by stem-end rot of some 
form or other, varying from a dry, withered rot to a moist, soft, and light 
brown colored rot more typical of the condition known as “jelly end” rot. 
The specific black fieldrot of potato tubers due to F. radicicola as stated 
to occur in Idaho ( 10 ) and eastern Washington (5) has not yet been re¬ 
ported to or seen by the writer in Oregon. The conditions in the eastern 
part of the State remain largely, however, still to be investigated. 
A stem-end rot of potato tubers occurs not infrequently during some 
seasons in western Oregon, and to some extent in the rest of the State, 
though in other seasons it is rarely encountered. It affects only the long 
tubers and varies widely in type and extent of rot at harvest time from 
a mere withering unaccompanied by discoloration of the stem end of the 
tuber as though a part of the water had been withdrawn from that por¬ 
tion, to a dry, wrinkled, sunken, rather tough, and light brown to black 
discolored condition of % inch or more of the stem end of the tuber, or to 
a soft and rather jellylike light brown colored rot extending back at 
times 1 % inches from the stem end, the rest of the tuber being sound and 
unaffected. In storage these diseased tubers often do not rot further, 
but the affected tissues frequently dry down and form a sharp line of 
demarcation from the sound, unaffected tissues unless stored under con¬ 
ditions unfavorable to the tubers. 
The cause of this rot in the State and the relationship of the different 
types manifested are not known, as it has been studied only incidentally 
when encountered in the course of other work. Generally the tubers 
appear similar to if not identical with the jelly endrot or the stem-end 
dryrot as described by Carpenter (2) of which Fusarium radicicola was 
said to be the chief cause. However, this fungus was isolated from 
only 12.2 per cent of the stem-end rot tubers cultured and listed in 
Table I, while the majority, 53.9 per cent, gave “miscellaneous fungi’* 
which were presumably saprophytic in most cases, and 8.8 per cent gave 
Verticillum albo-atrum and 4.5 per cent F. oxysporum . Tubers affected 
by this type of rot are, of course, readily entered by saprophytic organ¬ 
isms, and in many cases it is difficult if not impossible to determine from 
isolation cultures the primary cause of the trouble. However, the large 
variety of organisms secured in culture from affected tubers, the occur¬ 
rence of the trouble only during certain seasons without any apparent 
relation to the condition of the seed potatoes at planting time or to crop 
rotation, and the presence of F. radicicola in the stem end of so many 
