30 Colorado Experiment Station 
able damage. It is more destructive in the higher mountain val¬ 
leys than on the plains. Its presence on the vines can easily be 
distinguished by the brown lesions that occur along the base of 
the plant. In some cases, these wounds or lesions extend around 
the whole plant, and completely shut off the food supply from the 
leaves to the tubers. In most cases, only one side of the stem be¬ 
comes diseased, and in such cases the plant continues to grow, 
though the yield is considerably decreased. The disease may oc¬ 
casionally be found on the tubers in the form of small black spots, 
or wart-like growths all over the skin. These little dark areas 
vary in size from a pin-head to that of a dime. They are known 
as “sclerotia,” and contain the ‘Teed” which is carried over in this 
manner from year to year. During some years, the disease is par¬ 
ticularly bad and causes considerable damage. If the spots on the 
tubers are not large or conspicuous, they do not interfere with 
the salability of the crop. 
This disease can be controlled so far as dissemination from 
diseased tubers is concerned, by means of disinfection. While 
this method of treatment is efficient against the disease, it does not 
prevent infection from the soil, and hence the seed treatment 
against this disease does not always show satisfactory results. In 
this connection, it should be borne in mind that this disease is 
native to the soil, is always present, and under favorable condi¬ 
tions will attack the plant whether the seed has been treated or 
not. 
The most effective method of seed treatment is with corrosive 
sublimate, using 4 ounces of corrosive sublimate to 30 gallons of 
water. The solution should be made up in wooden vessels, such 
as a barrel, and the potatoes to be treated suspended in a gunny 
sack for one and one-half to two hours. This solution will pene¬ 
trate the “sclerotia” and kill them. The treatment should be 
made before the potatoes are cut. The potatoes treated cannot b^ 
used for livestock, as the solution is exceedingly poisonous, and 
care should be taken to protect livestock against drinking the so¬ 
lution. The solution can l)e used only three times, after which a 
new mixture should be made up. 
Potato Scab .—This well-known disease is common in every 
section of the State, and during some years does considerable 
damage to the crop. The disease is external, penetrating the tu¬ 
bers only to a very small extent. Its greatest damage is to the 
appearance and keeping quality. 
