298 
Journal of Agricultural Research 
Vol. VII, No. 6 
resistant to attack. The vigorous pathogenicity of this organism on 
the more susceptible species and varieties can not be questioned. The 
vigor of the attack on certain susceptible varieties of tobacco at least is 
as striking as that of any known root disease of plants (PI. 19). Since the 
fungus apparently spreads relatively slowly through the cell tissue, 
however, it seems apparent that soils must be abundantly infected and 
that a large number of local infections must occur before plants become 
badly diseased. Considering the wide range of hosts possessed by this 
fungus, it is possible that large economic losses, which are as yet rela¬ 
tively unknown, may be due to this fungus. In the case of tobacco 
alone it is certain that an average annual loss amounting to several 
millions of dollars occurs. Large losses also occur in the culture of 
violets (Viola spp.) and ginseng ( Panax quinquefolium). Little or 
nothing is known about the extent of the damage which may be done to 
the various cultivated leguminous crops under field conditions. It is 
believed that the fungus will become a serious disease of the peanut 
(Arachis hypogaea) and cotton (Gossypium spp.), if it has not already 
become one. 
SUMMARY 
(1) Thielavia basicola Zopf is a fungus parasite attacking primarily 
members of the Leguminosae, Solanaceae, and Cucurbitaceae. Other 
families containing hosts of this fungus are Araliaceae, Bignoniaceae, 
Compositae, Convulvulaceae, Cruciferae, Hydrophyllaceae, Malvaceae, 
Orchidaceae, Oxalidaceae, Papaveraceae, Polemoniaceae, Portulaceae, 
Primulaceae, Scrophulariaceae, and Violaceae. 
(2) Infection could not be obtained upon the following species of 
plants reported by others as hosts of T. basicola: Phaseolus midtiflorus , 
Nicoiiana rustica , Scorzonera hispanica, Daucus carota , Apium graveolens , 
Beta vulgaris , and Pastinica saliva. 
(3) Thirty-nine species of plants have been reported by earlier investi¬ 
gators as hosts of T. basicola . Thirty-two of the thirty-nine reported hosts 
plants have been grown in soil infected with T. basicola , and infection 
obtained upon twenty-five of these plants. Of the seven upon which 
negative results in infection were secured, it is believed that all should 
be excluded from the list of hosts until further corroboratory evidence 
of infection is obtained. The remaining seven species could not be tested, 
owing to the difficulty of getting seeds or plants. 
(4) Sixty-six new species of plants are added as hosts of T. basicola , 
of which twenty-eight are legumes, twenty are solanaceous plants, seven 
are cucurbits, and eleven belong to miscellaneous families. 
(5) A great difference in the susceptibility of the various species 
exists; and where earlier workers have been inclined to doubt the 
parasitism of T. basicola , it appears to have been due to the fact that 
infection experiments were carried on with what are now known to be 
immune or very resistant plants. 
