Feb. s. i9 J 7 
. Leafspot-Rot of Pond Lilies 
231 
In the writer’s experiments, carried out in the spring and summer of 
1913 at Kenilworth, D. C., Bordeaux mixture (3~3“5° formula) and 
soda-Bordeaux mixture (2-3-100 formula) were used. In both cases 2 
pounds of lead arsenate to 50 gallons of spray mixture were used to 
combat injurious insects, such as leaf channelers. 
The first treatment (May 29, 1913) was applied by spraying the respec¬ 
tive mixtures upon the leaves with a hand-pump outfit carried in a boat. 
Two varieties of N . odorata and several varieties of the tender day¬ 
blooming blue lilies were treated in this way, with an equal area of 
unsprayed plants of each variety left as control. Five other similar 
treatments were given on June 3, 10, 14, 19, and 25. The disease had 
gained a considerable start before the work was undertaken; hence, 
the control of the disease was not. as complete as it might otherwise 
have been. However, as shown by careful comparisons of sprayed and 
unsprayed plots (June 25 to 30), together with leaf counts with respect 
to injury, the plots sprayed with Bordeaux mixture were clearly 50 per 
cent less injured by the disease than the control plots. In the plots 
treated with soda-Bordeaux mixture the control of the disease was 
almost as high, but in this case a slight spray injury of the leaves was 
observed. 
During the following two seasons this treatment was continued by the 
owner on a commercial scale with satisfactory results. It might be 
added that the lead-arsenate treatment was found to be highly effica¬ 
cious in reducing the injury by leaf channelers. 
The ordinary Bordeaux mixture was slightly tfie better of the two 
mixtures in controlling the disease, and no spray injury resulted from its 
use. The soda-Bordeaux mixture, though almost as efficient in its 
control, and possessed of the advantage of not staining the leaves, 
caused some spray injury at the strength (2-3-100 formula) and fre¬ 
quency used. Obviously, with frequently submerged foliage, treatments 
must be made at rather close intervals in order to keep the upper surface 
of the leaves covered with a film of the fungicide. Apparently little or 
no infection occurred from the lower surface of the leaves. 
SUMMARY 
About the middle of May, 1913, the attention of the Laboratory of 
Plant Pathology was drawn to an irregular spotting and decaying of 
leaves of pond lilies (Nymphaea spp.) in the aquatic gardens at Kenil¬ 
worth, D. C. 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. From the olivaceous-black water-soaked spots 
