THE COTTONY LEAK OF CUCUMBERS CAUSED BY 
PYTHIUM APHANIDERMATUM 1 
By Charles Drechsler 
Associate Pathologist, Office of Cotton, Truck, and Forage Crop Disease Investiga¬ 
tions, Bureau of Plant Industry, United States Department of Agriculture 
INTRODUCTION 
While several species of Pythium, 
notably Pythium debaryanum Hesse, 
have been found destructive to a wide 
variety of phanerogams in the seedling 
stage, and inimical to the best develop¬ 
ment of some of these hosts in later 
stages, the association of the genus 
with decay of commercial vegetable 
products, representing parts of plants 
approaching maturity, has not been 
frequently recorded. Perhaps the most 
generally known instance is represented 
by the “leak” of potato ( Solanhm 
tuberosum L.) tubers, apparently en¬ 
countered by De Bary (I?) 2 in Germany 
more than four decades ago, and more 
recently made the subject of special 
study in the United States by Hawkins 
(8), A soft rot of sweet pepper ( Cap¬ 
sicum annum L., var. grossum) has been 
recorded by Lehman (5) from North 
Carolina as being due similarly to 
Pythium debaryanum, the decay always 
beginning at the blossom end, and 
affecting fruits not more than 6 or 8 
inches from the ground. The same 
fungus is mentioned in the list of fungi 
thriving on fruit in Belgium by El. and 
Em. Marchal (11), who observed it on 
a pear (Pyrus communis L.) lying on 
damp ground. 
MATERIAL EXAMINED 
This paper deals with a disease of 
cucumber (Cucumis sativus L.) fruit 
which the writer first observed in 
specimens submitted to him June 8, 
1922, by the food products inspector of 
the Bureau of Agricultural Economics 
at Washington, D. C., as being repre¬ 
sentative of a type of decay found 
responsible for considerable damage to 
a carlot shipped from St. George, S. C., 
June 2, 1922. Each fruit was entirely 
encased in a luxuriant cottony mycelial 
weft, matted down here and there as a 
wet membranous layer, at first sight 
thus suggesting being wrapped in 
absorbent cotton that had become mois¬ 
tened in places. The tissue in the 
interior was found very watery and of a 
peculiar texture, greatly softened, and 
so lacking in mechanical firmness as to 
be divided very readily with blunt 
instruments. Where not occupied by 
secondary bacterial invaders, the juices 
draining copiously from the incisions 
were only slightly turbid. The mate¬ 
rial gave off a peculiar odor rather 
inadequately described by the term 
“marshy”—not pleasant, but having 
little in common with the putrid smells 
characteristic of the decay of vegeta¬ 
bles due to bacteria. ‘ 
Since the original discovery of the 
trouble no additional material has been 
submitted to the writer, and from in¬ 
quiry it would appear that the type of 
deterioration in question is not fre¬ 
quently encountered on the Washing¬ 
ton market, or at least not in quantity. 
However, early in July, 1924, J. I. 
Lauritzen found several carload lots in 
both the Pittsburgh and the Buffalo 
markets, of which not inconsiderable 
portions were affected in exactly the 
manner described in the preceding par¬ 
agraph. Almost simultaneously G. B. 
Ramsey observed the same decay with 
its characteristic display of cottony 
mycelium in a carload lot of cucumbers 
on the Chicago market, the shipment 
in this instance having originated in 
North Carolina. It is highly probable 
that in the case of the cucumbers 
grown in the Southeastern States the 
destruction from this trouble will gen¬ 
erally be found greatest in the markets 
of our more remote northern cities, 
since, other things being equal, the 
quantity of cucumbers affected evi¬ 
dently increases with the length of 
time the shipment is in transit. 
Microscopic examination of the spec¬ 
imens obtained on the Washington 
market revealed the fresh cottony 
growth as a mass of mycelium composed 
of nonseptate hyphae. Where the 
weft had been matted down as a wet 
membranous layer closely adhering to 
the substratum, innumerable thou- 
1 Received for publication, Aug. 20, 1924; issued August, 1925. 
2 Reference is made by number (italic) to “Literature cited,” p. 1042. 
Journal of Agricultural Research, Vol. XXX, No. 11 
Washington, D. C. June 1,1925 
Key No. G-427 
52243—25t- 
-4 
(1035) 
