460 
Journal of Agricultural Research 
Vol. XXVI, No. 10 
by the important parasite Fusarium, here described as a new variety of 
Fusarium martii App. and Wr., and contains notes upon other species of 
Fusarium which have been isolated frequently from diseased pea plants, 
or which have been mentioned in literature as parasites. The diseases 
caused by the other parasites mentioned above will be treated in subse¬ 
quent papers. 
THE DISEASE 
DESCRIPTION 
The disease caused by Fusarium, unfortunately, does not exhibit any 
symptoms upon the aerial portion of the plant that are different from 
those produced by several other diseases. A considerable decay of the 
cortex of the stem occurring late in the development of the plant may 
not cause any apparent unfavorable effects upon growth. If many 
roots are destroyed, growth may be retarded, and an invasion of the 
vascular bundles of the stem may cause a wilt of the entire plant. Since 
the invasion of a plant by one of the other parasites may cause all of 
these degrees of injury, and the other diseases may produce some of 
them, the distinguishing characteristics of the disease must be sought in 
the region which the fungus has penetrated. 
The most susceptible portion of the plant is the base of the stem above 
the point of attachment of the cotyledons. The largest amount of 
damage is done when the fungus enters at this point and causes such 
disintegration of the tissues that the taproot is separated from the 
stem. At higher soil temperatures the vascular bundles turn a charac¬ 
teristic reddish brown, and the plant wilts; at lower temperatures the 
connection between root and shoot may be completely rotted off, forc¬ 
ing the plant to depend entirely upon roots which are developed above 
the point of injury. The lesion which the fungus produces at its point 
of entry is easily distinguished, at least in its early stages, by its color 
and shape. In color it is reddish brown or chocolate, in form it is elon¬ 
gate, often wedge-shaped with the base of the wedge at the point of 
attachment of the cotyledons and the apex pointing upward. Lesions 
are not sunken until they are extensive. If the lesion reaches the vas¬ 
cular tissue this takes on a bright orange red or brown color that may 
extend above the external lesion as far as the first node. The lesion 
caused by Fusarium is distinguished from that caused by the phycomy- 
cetous fungi by its darker color, and from that caused by Rhizoctonia 
by its shape, and the absence of a sunken eroded surface. 
The disease is found as a decay of the taproot or of any of the smaller 
roots. Dark lesions occur along the roots and the ends of roots are 
killed, but this form of the disease can not be distinguished readily from 
that caused by Rhizoctonia. 
ECONOMIC IMPORTANCE 
It is not difficult to discuss the economic importance of the entire group 
of diseases causing decay of the roots and base of the stems of the pea 
plant. The present recognition by pea growers of the necessity for the 
rotation of crops has been brought about by very costly experience to 
the factory owner and grower alike. Even now the number of fields 
damaged by disease is considerable, even in districts where most intelli¬ 
gent care is taken in the selection of suitable fields for the crop. 
