LEAFSPOT-ROT OF POND LILIES CAUSED BY HELI- 
COSPORIUM NYMPHAEARUM 
By Frederick v. Rand, 
Assistant Pathologist, Laboratory of Plant Pathology, Bureau of Plant Industry, United 
States Department of Agriculture 
INTRODUCTION 
About the middle of May, 1913, the attention of this laboratory was 
drawn to an irregular spotting and decaying of leaves of pond lilies 
(Nywphaea spp.) in the aquatic gardens at Kenilworth, D. C. The disease 
was first noticed in the greenhouse propagating tanks, where some of the 
tender lilies were being started prior to setting in the open ponds. In 
some cases all the leaves succumbed, so that plants thus affected were too 
weakened for profitable growth during the following summer. As the 
season advanced, the disease appeared also in the open ponds, upon both 
the tender and the hardy varieties of pond lilies, and the inroads upon 
the leaves were so severe as to demand an attempt at control. From the 
general appearance of the leaf injury and its rapidity of spread from 
affected leaves it seemed evident that the disease was of a parasitic 
nature. On account of the severity of the disease in this particular 
locality and season, the present study was undertaken primarily to test 
the efficacy of spraying the floating leaves of a water plant with ordinary 
fungicides. However, the causal fungus itself proved so interesting that 
considerable time has also been devoted to a study of its characters and 
relation to the host. As demonstrated by similar signs on the host, isola¬ 
tion of the same fungus, and its successful inoculation into healthy pond- 
lily leaves, this disease has also been found by the writer at Arlington, 
N. J., at the Brooklyn Botanical Gardens, Brooklyn, N. Y., and at the 
New York Botanical Garden, New York City. 1 .An apparently identical 
leaf disease was likewise seen at Riverton,* N. J., though no cultures 
were attempted from this locality. Hitherto, so far as ascertained, no 
data upon this disease have been published. 
SIGNS OF THE DISEASE 
The disease first appears in the form of tiny dark specks on the leaf 
blade. (PI. 67, A). In those varieties with red pigment in the cells of 
the lower surface, the initial specks are often reddish or bordered with 
red, as seen from the upper surfaces of the leaves. At first roundish in 
outline, the spots become more or less irregular with an increase in size 
until, either individually or by the coalescence of several initial infection 
1 The fungus from the New York Botanical Garden was isolated by Mrs. Ella M. A. Enlows, of the Bureau 
of Plant Industry. 
Vol. VIII, No. 6 
Feb. s, 1917 
Key No. G—ios 
Journal of Agricultural Research, 
Washington, D. C. 
hb 
74549°— 17 - 3 
(219) 
