Potato Growing in Colorado 27 
t 
destroy the whole plant. Such seed may be used for feeding ani¬ 
mals, but should under no circumstances be planted. 
There is no known remedy that is effective against this disease; 
only precautionary measures can be taken, such as rotation of the 
crop and the planting of seed free from the disease. 
The appearance of the disease in the field is, in some cases, 
almost identical with the Early Blight, with the exception that the 
leaves turn a paler shade of yellow and do not show the brown 
patches and circles. The stem is also- attacked, and if a cross-section 
is made of the stem close to the ground, dark areas will be found 
in the bundle or fiber portion of the stem. These dark areas indicate 
the presence of the disease, and greatly interfere with the transpor¬ 
tation of food materials up and down these fibers or vessels in the 
stem. It is also maintained that the curling of the leaves some¬ 
times present in many of our potato 1 fields is caused directly or in¬ 
directly by the same fungus. Undoubtedly other factors contri¬ 
bute to the presence of the trouble known as the “Curly Leaf 
Diseased 
Rhizoctonia .—This disease is present in practically all of our 
cultivated fields, and under favorable conditions will do considerable 
damage to the crop. The presence of the disease on the vines can 
be distinguished by dry rot or lesions that occur at the base of the 
stem from the ground upward. In some cases these lesions or , 
wounds extend around the whole stem and completely shut off the 
food supply. In other cases, the disease attacks only one side of 
the stem and does not completely cut off the supply of food to the 
roots, but curtails the food supply and lessens the production of 
tubers. The disease may occasionally be found on the potatoes in 
the form of black spots or wart-like growths all over the skin. (See 
figure No. 9.) These little areas vary in size from a 
pin-head to the size of a dime. They are black and corky in struc¬ 
ture and are known as sclerotia. These structures carry the spores 
over from year to year and reinfest the crop. A careful examina¬ 
tion of potato fields in the State this year show that this disease is 
very prevalent. In one section of the State the writer was unable 
to find a single tuber that did not have some sclerotia present on it. 
This disease seems to thrive on dry land as well as on that which 
is irrigated, but seldom develops to a dangerous point on the dry 
lands. 
The disease can be controlled, so far as disseminating it from 
diseased tubers is concerned, by means of disinfection. The most 
effective method is a corrosive sublimate treatment, using 4 ounces 
of corrosive sublimate in 30 gallons of water. The solution 
may be made up in a barrel and the potatoes placed in a gunny 
