26 
The Coeorado Experiment Station. 
Rhizoctonia and Scab. Other diseases, as early blight, which is a 
leaf trouble, sometimes attack potatoes over the state, but it is rarely 
necessary to employ preventative measures against these. 
Fusarium gains entrance to the plant from the soil, and, by 
growing in the stem, shuts off the water supply, causing the vine to 
wilt. If a section of the stem is cut, the sap wood will show a 
darkened appearance not found in healthy plants. Areas where the 
trouble occurs should not be planted to potatoes again for four or 
five years, thus starving out the fungus. In addition to damaging 
the growing crop, this disease also causes dry rot of potatoes in 
storage. 
Rhizoctonia also attacks the plant from the soil, and works on 
the lower portion of the stem. It restricts the downward flow of 
food material which has been prepared in the leaves, thus prevent¬ 
ing the development of the tubers. Rotation, together with the use 
of clean seed is the only remedy. 
Scab is another fungus trouble and causes unsightly, rough 
spots on the tubers, reducing their value on the market. One of 
the most common preventatives against scab is seed treatment. The 
uncut tubers may be soaked for two hours in a solution of four 
ounces of corrosive sublimate in thirty gallons of water. This so¬ 
lution is very poisonous and care must be used so that animals will 
not gain access to either the solution or the tubers which have been 
soaked therein. Crop rotation should also be practiced. Greening 
of the seed for a time, before planting, has also been recommended. 
Seed Potatoes .—The question of pure seed is of vital import¬ 
ance to the potato growers of the state. Not only should the seed 
be true to type but they should be free from diseases. It is also im¬ 
portant that in choosing the variety for a given section of the state 
attention must be paid to the question of maturity, as some of the 
standard varieties will not mature in some districts of the state and 
it would be useless to plant them. Then due attention should be 
pa d to one or two standard varieties. In order to> secure a favor¬ 
able market, enough should be grown of each variety to insure car¬ 
load shipments. The question of importing the seed from year to 
year is of especial importance to the older potato growing districts. 
These sections are now more or less infested with diseases that pre¬ 
clude the using of their own crop for seed the following year and 
seed must be obtained from other portions of the state or outside 
of the state where the disease is not known. There should be a cor¬ 
relation to mutual advantage between the potato growers in the 
mountain section and the potato growers in the valleys or on the 
plains, so that the latter can obtain their seed from the former. 
