Fusariiim Blight of the Soy Bean 
33 
Table 6. — Influence of soil types on percentage of infection hy 
Fnsarium sj)p. in the presence of the nematode 
(Heterodera radicicola). 
Type 
Total 
number of 
plants 
Number 
with 
nematodes 
Per cent 
with 
nematodes 
Number 
with 
Fusarium 
Norfolk coarse sand 
25 
4 
16 
0 
Norfolk sand 
30 
8 
26.6 
0 
Norfolk fine sand 
34 
8 
23.5 
0 
Norfolk very fine sand 
34 
6 
17.6 
0 
Norfolk coarse sandy loam. . . 
33 
5 
15.1 
0 
Norfolk sandy loam 
33 
8 
24.2 
0 
Norfolk fine sandy loam 
31 
4 
12.9 
0 
Norfolk very fine sandy loam . 
25 
7 
28.0 
0 
Norfolk loam 
15 
12 
80.0 
0 
Norfolk silk loam 
17 
1 
5.8 
0 
Norfolk clay 
30 
0 
0.0 
0 
1 
Xone of the plants were infected by the fungus and conse- 
quently tl^e original purj)ose, for which the experiment was 
planned, failed. The results, however, are included since they 
furnish some evidence that previous failures of a similar nature 
were not due primarily to the use of soils of unsuitable type, 
water holding capacity, or humus content. The percentage of 
infection of cowpeas, however, seems to be increased when grow- 
ing in inoculated soils containing an excessive amount of humus. 
THE INFLUENCE OF ACIDITY AND ALKALINITY 
Xo definite experiments have yet been ^undertaken to deter- 
mine the influence of soil acidity on the develoj)ment of the dis- 
ease, but field observations indicate that it is not a factor of pri- 
mary importance. Thej^ have shown that the cowpea wilt is 
destructive on soils varying considerably along the plus and minus 
scale of acidity. 
A similar conclusion can be drawn from the following cul- 
tural studies. Two strains of F. tracheipliilum^ one from cowpea 
and one from soy bean, were grown on a culture medium whose 
reaction was varied from +40 to — 40 (Fuller’s scale) by the 
addition of standard solutions of XaOH and HCl to a standard 
