POTATO FAILURES. 
5 
duced which give promise of an abundant yield, but when 
digging time comes it is found that so few tubers have set 
that it does not pay to dig them. Many of the thriftiest 
vines fail to produce a single tuber. (See Plate V.) It is a 
less frequent, but by no means uncommon occurrence, for 
the vines to set an abnormal number of small potatoes, or 
'‘Little Potatoes’' as they are sometimes called. These 
often occur in compact clusters and are so small as to be 
worthless. (See Plate IX.) The above conditions occur 
most frequently on poorly drained land and especially on 
the heavier soils. A third condition and one which is 
common to the best potato districts is the dying of potato 
plants thus resulting in poor stands. Our experiments 
prove that any of these conditions may be produced by at¬ 
tacks of Rhizoctcnia, and in the vicinity of Fort Collins, 
where most of our experiments and field work were done, 
this fungus is frequently responsible for the lack of success 
in the growing of this crop. So far as we have been able to 
learn, one or more of these conditions prevail in many sec¬ 
tions where the potato crop is a failure. 
The question naturally arises why this fungus should 
be so severe in its attacks on the potato at Fort Collins 
while the crop is so successfully grown in the Greeley dis¬ 
trict, twenty miles east and nearly the same altitude. Many 
farmers claim that if they had Greeley soil they could grow 
potatoes as successfully as those in the favored section. 
Our observations go to show that the difference between 
success and failure in potato growing is principally a differ¬ 
ence in soils, not that the successful growers suffer no loss 
from the attacks of this fungus but that it finds less congen¬ 
ial surroundings in the lighter and better drained land. 
NATURE OF THE FUNGUS AND ITS METHODS OF ATTACK. 
The hyphae or root-like organs of the fungus are often 
found growing on the surface and in the scab ulcers of pota¬ 
toes. These hyphae give rise to irregularly shaped dark 
masses know as sclerotia, which vary in size from that of a 
mere speck to areas one-half inch or more in diameter. 
(See Plate I. Fig 2.) The sclerotia resemblesmall bits of earth 
so closely that it is often difficult to distinguish them from 
particles of soil on the tubers, but by placing the potatoes 
in water these bodies become black and quite conspicuous. 
Many of them adhere very firmly. When such potatoes are 
used for seed the disease is planted with them and it is 
ready to begin its attack as soon as the new plants start to 
develop. 
