HOST PLANTS OF THIELAVIA BASICOLA 
By James Johnson, 
Assistant Horticulturist , Wisconsin Agricultural Experiment Station 1 
The increasing economic importance of Thielavia basicola Zopf as a 
root parasite of certain cultivated plants has led to a desire for more com¬ 
plete information regarding its range of host plants. This knowledge is 
important not only from the standpoint of the effect upon the hosts 
themselves but in the relation of the use of these host plants in rotation 
with other crops susceptible to attack by the fungus. T. basicola appears 
to be primarily a parasite of leguminous plants, and the common use of 
these in rotation may prove to be unprofitable for certain crops. The 
benefit derived from the added fertility in the soil may be entirely offset 
in certain instances by the injury done as a result of maintaining the 
fungus in the soil through the use of host plants in rotation. 
From a mycological point of view, considerable interest may also be 
attached to the hosts of T. basicola . The earlier botanists who observed 
this fungus were in some doubt as to the parasitic nature of the organism. 
This view has persisted to some extent, and the fungus is still believed by 
some to be purely superficial in its mode of life and not ordinarily injurious 
when present. On the other hand, some of the later investigators have 
not only convinced themselves of the parasitism of the organism but also 
of a high degree of pathogenecity, while some have gone so far as to sup¬ 
pose the fungus capable of attacking almost any plant under favorable 
conditions (n). 2 It is fairly clear to the writer that this difference in 
opinion is due in a large measure to not only the species but the variety of 
host plant under observation. Considerable emphasis has also been laid 
upon the conditions necessary for disease to be developed by this fungus, 
leading to the supposition that certain unknown special conditions are 
necessary and that infection is difficult to obtain. Although this may 
be true within certain limits, it has been found that infection could be 
repeatedly and easily produced with the more susceptible plants. Where 
the writer has experienced difficulty in obtaining infection on certain host 
plants, it has been attributed rather to resistance or immunity in the 
1 This investigation was carried on in cooperation with the Bureau of Plant Industry, Department of 
Agriculture. 
2 Reference is made by number to “Literature cited,” p. 299-300. 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
iz 
(289) 
Vol. VII, No. 6 
Nov. 6,1916 
Wis.—6 
