HYDROGEN-ION CONCENTRATION AS RELATED TO THE 
FUSARIUM WILT OF TOMATO SEEDLINGS 1 
Everett Clifton Sherwood 
(Received for publication January n, 1923) 
It has recently been shown by Jones (15) that phytopathologists should 
give especial consideration to the relations of environment to predisposition. 
Johnson and Hartman (14) have emphasized particularly the importance of 
certain soil factors in the development of those diseases which attack the 
underground parts of plants. The investigations reported in this paper 
were planned to determine the possible relation of soil reaction to the de¬ 
velopment of the wilt of tomato {Ly coper sicon esculentum Mill.) caused by 
the soil parasite Fusarium lycopersici Sacc. The work was coincident with 
Clayton’s recently published studies on the influence of temperature (3) and 
of moisture (4) upon the development of this disease and was designed to 
supplement those investigations. It was, indeed, begun in immediate 
association with Dr. Clayton, and the author is indebted to him both for the 
initial cultures of Fusarium used for soil inoculation and for much critical 
attention in the consideration of evidence as the problem was developed. 
The only paper coming to the attention of the writer which deals directly 
with the influence of soil reaction upon the development of the Fusarium 
wilt of tomatoes is that of Edgerton (5). He reports that an application 
of lime at the rate of ten tons per acre reduced the disease in the seed bed 
from 51.0 percent to 4.4 percent. In the field the wilt was reduced in the 
Acme variety from about 77 percent to 40 percent, and in the Earliana from 
about 75 percent to 23 percent. The reaction of the soil before liming was, 
however, not reported. He found also that a variety of tomatoes showing 
high susceptibility to the disease in the seed bed manifests the same degree 
of susceptibility in the field. 
Few references were found with respect to the effect of liming on the 
growth of tomatoes. Mooers (17) concluded that they are only moderately 
benefited. He based his conclusions on tests made in soils where liming was 
necessary to secure a fair crop of clover. Hartwell and Damon (9) found 
that liming resulted in a slight decrease in yield on one plot which required 
2500 pounds of calcium oxide per acre to neutralize the soil according to 
the Vietch lime-requirement method. They reached the conclusion that 
tomatoes are tolerant of a moderate degree of acidity. The exact reaction 
of the soil after liming, however, was not determined. 
1 Investigations carried on at the University of Wisconsin under advisory relations with 
Professor L. R. Jones, to whom the author is indebted for counsel and criticism. 
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