Apr. 7.1933 
Influence of Soil Temperature on Fusarium in Cabbage 65 
was about 26° and in the Wisconsin Hollander about 29°. These tem¬ 
peratures practically coincide with that for growth of the causal organism 
on potato agar, but are several degrees higher than the optimum for 
growth of the seedlings. These results differ from those reported by 
Tisdale (ij) for flaxwilt and those reported by Clayton (5) for tomato 
wilt only in that the optimum temperature for growth of the cabbage 
plant is lower than that for development of the disease and growth of 
the parasite. The same temperature relations do not obtain for other 
types of diseases attacking the underground parts of plants. Balls 
(i, 2) reported that the soreshin disease of cotton developed most 
destructively at 17® to 23° C., while the optimum for the growth of host 
and parasite was about 28°. Johnson and Hartman (9) reported quite 
similar relations for the rootrot of tobacco. 
Fig. 5.—Comparison of development of yellows in Commercial Hollander and Wisconsin Hollander seed¬ 
lings given in Table V, grown ao days from seed in artificially inoculated soil. 
Although the percentage of yellows in the resistant Wisconsin Hollander 
was rather high during the early period of growth, it was lower at all 
temperatures than that of the susceptible commercial strain. The 
greatest differences in percentage of yellows between the two strains 
occurred at 20° and at 35° C., where they amounted to about 35 per 
cent. In artificially inoculated soil at 26*^ and above the two strains 
seemed to be equally susceptible (fig. 5). The cause for such a wide 
difference between the pathogenicity of Fusarium conglutinans in 
naturally and in artificially inoculated soil has not been determined. 
It is apparent, however, that this difference is in part due to the direct 
relation of the higher temperatures to the stimulation of the Fusarium. 
Tliis relation becomes especially evident when the fun^s is growing in 
pure culture free from the complicating relations with the normally 
associated soil flora. 
Other workers have obtained similar results with vascular parasites. 
Edgerton (6, 7) found that a much higher percentage of Fusarium-wilt of 
tomato developed in the sterilized, reinoculated soil than in the unsteril- 
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