July 1, 1924 
55 
Pythium Rootlet Rot of Sweet Potatoes 
The writer has made no study of the 
species causing Pythium rootlet rot. 
The taxonomy of the causal organisms 
will be handled by Dr. Chas. Drechsler, 
who is making a monographic study of 
the genus. Judging from a preliminary 
istudy of the large number of cultures 
Doctor Drechsler has already obtained 
from the sweet-potato roots, it is not 
unlikely that two or three species of the 
debaryanum type may be identified. 
SUMMARY 
The Pythium rootlet rot of sweet 
potatoes occurs quite commonly in the 
hotbeds in various parts of the country. 
The disease apparently has its begin¬ 
ning at the end of the small rootlets 
and works progressively up the root. 
Investigations have shown that all 21 
varieties tested are susceptible to the 
disease, but not to the same degree. 
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