40 
The Colorado Experiment Station. 
Dry Rot in Potato Tubers is also chiefly caused by the fungus, 
Pusarium, and is most common on bruised or cut tubers and where 
the potatoes are stored in unventilated or warm cellars, or where 
dealers and town people keep potatoes in warm places. As stated, 
the use of such seed is very apt to infect the new plant, to the serious 
damage of the stand and yield. This matter of dry rot is exceed¬ 
ingly important especially to the growers of Rural and Ohio pota¬ 
toes and to the consumer. The dealer’s warehouse and the out-of- 
the-way, little-visited farm cellar, set in the field or in some side 
hill, are great sources of infected seed, poor crops, and unsatisfac¬ 
tory table potatoes. 
Internal Brown Spot is a disease affecting, in our region, the 
tubers of the Early Ohio potato, almost exclusively, and though it 
occurs from California, Idaho and Montana to Texas, we have not 
known of a case of this trouble under the ditch. It* is thought not 
to be of bacterial or fungous origin but to be a physiological matter, 
the death of some of the cells. The cause is supposed to be drouth, 
and the remedy is the raising of other varieties than the Ohio, and 
better dry farm methodsf that shall supply water enough for the 
plant. 
Internal Brown Spot does not destroy the tuber nor hurt its 
outside appearance nor preclude^ its use as seed; but the spots do 
prevent its sale and as found by the potato specialist in Nebraska 
and Colorado, seriously damage the odor, flavor and appearance. 
In close competition, we have found the odor and flavor in samples 
where the spots could not be seen. 
Potato Scab. —This disease occasionally makes its appearance 
in every Colorado potato field. In the east nearly all writers have 
thought that scab was caused from a fungus, Oospora scabies. 
German pathologists have proved that several other fungi may cause 
scab, and in Colorado Professors Rolfs and Paddock found that 
much potato scab was caused by the Rhizoctonia stage of Corticum 
vagum. More recently we have demonstrated that this is true. 
*Nebraska is a leading producer of Ohio potatoes and without irri¬ 
gation, and the disease has been very serious in that State. Dr. E. M. 
Wilcox of the Nebraska Station and his assistants have spent an immense 
amount of time on this disease, without isolating any organism as the 
cause. 
tSummer tillage the previous season and summer or fall plowing, 
with thorough shallow tillage up to and after planting. 
$Sutton & Sons, the well known British seedsmen, performed in 1906 
an experiment as to whether tubers affected with this spot were good 
seed. They found with two varieties that the healthy seed produced a 
larger crop by one-fourth to one-half but that there was not more brown 
spot from the affected than from the unaffected seed. In fact there was 
far less from the affected seed, doubtless because it grew less rank and 
used less water and suffered less from drought, which in Great Britain, 
as with us, is thought to be the cause. 
