Jan. 6 ,1923 
A Phytophthora Footrot of Rhubarb 
7 
Pathogenicity was completely proved later. Meanwhile a large number of 
rhubarb roots of standard varieties had been obtained from a seedsman. 
These were planted, both in a field plot and in flowerpots in the green¬ 
house, at Arlington Farm. In the greenhouse further inoculations were 
made on the large plants obtained from roots, and these were almost 
invariably successful, resulting in the majority of cases in the death of 
the whole plant and the decay of the root. Inoculations made into both 
the aerial parts and the roots gave this result. Plantings made in the 
spring in the commercial grower’s field to replace plants that had been 
killed by the disease the previous season resulted in the decay and death 
of the new plants. Inoculations into large, vigorous plants in the field 
at Arlington Farm, made by applying the fungus from pure culture at the 
base of a stalk where moisture is abundant and growth is rapid, resulted 
not only in the death of the particular stalk inoculated but in the rapid 
destruction of the entire plant. 
It became necessary to discontinue the investigation of this problem 
about midsummer, 1918, in order to take up important war emergency 
work. Except for the maintenance of cultures and occasional observa¬ 
tions, it was not until the summer of 1920 that the writer was again able 
to devote any considerable attention to the problem. Early in July, 1920, 
the experimental field at Arlington Farm was in vigorous growing condi¬ 
tion, and none of the disease was evident. Another series of inoculation 
experiments was started under these conditions. When the inoculations 
were made the weather was not altogether favorable for infection, and 
water and shade were applied artificially, as indicated below. A period 
of wet weather followed immediately after, however, and this resulted not 
only in the rapid development of the fungus in plants inoculated but also 
apparently in its spread to other plants. The experiment is reported in 
detail in Table I. 
