Plant Diseases of 1901 . 
15 
fields showed evidence of its presence. I examined one tract of land 
that had been sown to peas at the usual time in the spring. Most 
of the seed failing to grow, the ground was plowed and again sown 
to peas. At the time of my visit the field had the appearance of 
fallow land, as only an occasional pea plant was to be seen. 
The soil in the vicinity of Longmont is well adapted to pea 
growing, about 2,500 acres being grown there annually to supply 
the canning factory, which makes a specialty of this product. The 
fields in which the disease made its appearance have always pro¬ 
duced good crops of other kinds. A good crop of wheat grew the 
vear before on the one that I examined. 
-«/ 
My attention w T as called to this disease first in September of 
1900, when I took up the work of this department, but no investi¬ 
gations could be undertaken at that time. During the following 
winter some soil was secured from an infected field, which was 
placed in flats in the greenhouse and sown to peas. 
The plants grown in this soil were nearly all attacked by fungi 
on the roots and on the stems below ground. The injury was not 
severe enough, however, to kill them, and as the vines grew and 
bent over they were attacked at the point where they came in con¬ 
tact with the earth. These diseased areas were soon overrun by 
various saprophytic fungi, so it was difficult to tell what was the 
real cause of the trouble. However, there was a large colored hypha 
constantly present in the diseased parts and the same hypha was 
found to be abundant in specimens collected in the field by Mr. 
Potter the summer before and preserved in formalin. 
All attempts to cultivate the fungus artificially failed, since 
it produced no spores and the diseased areas on the stems 
were so contaminated with other forms that efforts to secure 
cultures by other means failed. The distinctive character of the 
hypha showed that it belonged to a group of fungi commonly known 
&s Rhizodonia, and that it was closely related to if not identical with 
the disease that is so destructive to potatoes in this State. 
The soil was then turned over to Mr. Rolfs to determine whether 
it was infested with this potato fungus with which he was working. 
A part of it was placed in pots and planted to potatoes. Eight pots 
were planted with clean potatoes that had been treated with corros¬ 
ive sublimate to free them from disease. The soil in another lot of 
eight pots was sterilized with steam for three days, two hours a day, 
to kill all plant life that it contained. These pots were planted with 
clean potatoes treated as above. In the first series all the plants 
were affected with Rhizodonia. In the second all of the plants, with 
one exception, were free from the disease. The presence of the 
fungus in the one pot may easily have been due to carelessness in 
watering, as it stood by the side of the others that contained the un¬ 
sterilized soil. 
