Dec. 8,1923 
Fusarium Stem and Rootrot of Peas 
461 
Since the disease caused by Fusarium is only one of four diseases which 
are usually operating jointly to bring about the economic consequences 
indicated, and since these diseases do not have distinct characters which 
enable one to differentiate them with certainty, a statement of the 
relative importance of any of them is at present largely a statement of 
personal opinion which must be held subject to revision. Taking into 
consideration all the territory that has been examined, the writer is 
inclined to believe that the diseases due to the two phycomycetous species 
cause by far the largest part of the loss; that the disease caused by Fusa¬ 
rium is second in importance, while that caused by Corticium vagum is 
of much less importance than either of the preceding. Local variations 
in this order of importance are brought about by environmental condi¬ 
tions which especially favor one or another of these diseases. 
DISTRIBUTION OF THE DISEASE. 
All of the root parasites of peas are nearly coextensive in their distri¬ 
bution. The disease caused by the species of Fusarium has been found 
in scattered localities near the Atlantic coast from Maine to Florida, in 
all the North Central States and Minnesota, and in Montana and Utah. 
Search has not been made in any of the Pacific Coast States. The only 
important pea-growing district that has been searched in vain thus far 
is in Idaho. The dissemination of the disease within the districts where 
it occurs varies greatly, depending apparently upon the two factors—the 
length of time during which peas have been grown in that district and 
the frequency with which they have been planted on the same land. 
There are few localities which have been examined in which peas have 
been grown more than 10 years intensively upon narrowly limited areas 
in which this disease has not become a more or less important factor 
which is reducing yields. The climatic conditions which determine, in 
large measure, the amount of damage that it may do are discussed later. 
For the present it is sufficient to say that the disease is distributed very 
thoroughly throughout the most of the pea-growing area of the United 
States. 
PREVIOUS RECORDS OF PEA DISEASES CAUSED BY SPECIES OF 
FUSARIUM 
Serious stem and rootrots of peas caused, or believed to be caused, by 
species of Fusarium have been noted several times in Europe and Amer¬ 
ica, and have been studied at several points in Europe. The first of these 
to receive serious attention was the so-called St. John's disease of peas 
in Holland reported by Van Hall in 1903 ( 8). 2 The description of the 
disease is not given in sufficient detail to enable us to distinguish it from 
other diseases now known. It is said to remain in spots in fields for a 
long time. From dying plants Van Hall isolated a Fusarium which he 
regarded as very similar to F. vasinfectum f Atk. and which he designated 
variety pisi of that species without description. The pathogenicity of 
this fungus was tried in a single experiment upon plants grown in water 
culture, though Van Hall admits that the infection which he obtained 
in this manner is not an adequate proof of pathogenicity. 
Later Schikorra (n) found what he believed to be Van Hall’s St. John’s 
disease. He mentions a yellow color of the center of the stem above 
* Reference is made by number (italic) to “Literature cited,” p. 475. 
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