470 
Journal of Agricultural Research 
Vol. XXVI, No. io 
In order to obtain field evidence of the persistence of the fungus in 
different types of soil and to provide suitable plots for the trial of varieties 
of peas for resistance, a number of plots of soil supposedly free from all 
root-infesting parasites of peas were inoculated with the fungus and 
planted with inoculated seed in much the same way as in the greenhouse 
trials already discussed. Inasmuch as certain of these plots could not be 
critically examined later for results while others were found infested with 
other parasites which made results valueless, only two plots at Madison 
are regarded as highly significant. Since no inoculations with Fusarium, 
with one possible exception, have given infection that affected yields, 
the progress of the disease has been determined by examination of plants 
removed from the soil from time to time for the reisolation of the 
fungus. Among the inoculated plots besides those at Madison, Wis., 
was one at Arlington Experiment Farm, Va., planted first in 1919 on 
well drained clay soil. The writer was unable to observe the peas grown 
on this soil in 1920, but in 1921 peas grew without a trace of infection 
from this fungus. A small inoculated plot at McMillan, Mich., planted 
first in 1920 on sandy soil low in humus, gave plants with only a few 
slight lesions on the bases of the stems, though in a field close by, on 
similar soil high in organic matter and long used for pea growing, there 
was much of the disease present. At Madison only two plots remained 
free from other diseases during three years, thus permitting observations 
of the effect of Fusarium alone. One of these plots was on a well drained 
gravelly loam low in humus; the other was on a reclaimed marsh where 
organic matter was abundant. On the loam 12 varieties were planted 
on April 25, 1919, in rows 20 feet long, the soil and seed in one-half of 
each row being inoculated with the same strain of the Fusarium that had 
been used in the greenhouse inoculations. Three of the early varieties 
showed a few dying plants toward the end of the growing season, but on 
the whole it was difficult to distinguish by appearance the inoculated 
from the noninoculated plants. Peas were returned to this ground the 
following year with even less infection. In 1921 peas on the inoculated 
soil showed no typical Fusarium disease and could not be distinguished 
from controls when roots were examined. Since the ground was not 
available for peas the fourth year, some of the soil was brought into the 
greenhouse during the following winter and planted with peas at an 
optimum temperature for the development of the disease. No infected 
plants were obtained. A similar plot of soil inoculated in 1920 gave 
plants free from disease in 1921. 
That this type of soil was not unfavorable for the development of all 
root parasites is demonstrated by the fact that two short rows inoculated 
with soil brought direct from diseased fields gave plants showing visible 
symptoms of disease produced by Aphanomyces sp. and the amount of 
injury to plants increased in the two succeeding years, spreading to 
adjacent rows. 
The other plot started in 1919, at Madison, was on muck soil and was 
not planted until June 30. As might be expected, because of the high 
temperatures prevailing at that time of year, all the plants were rotted off 
at the seed and managed to maintain a stunted existence only by means 
of rootlets sent out above the point of injury. This area was replanted 
in 1920 without further inoculation, and the disease appeared as de¬ 
structively as in the preceding year. The second replanting in 1921 still 
gave disease in undiminished severity, equaling that in a newly inocu¬ 
lated plot, while the control plot remained free from disease. 
