Nov. 8 , 1915 
Dissemination of Bacterial Wilt of Cucurbits 
259 
collected in field No. 1, where presumably they had hibernated. Within 
a week several plants in 1 of the 2 cages in field No. 1 into which the 
beetles had been introduced showed signs of wilt, starting from points 
in the leaves gnawed by the beetles. Upon cutting off the stems the 
typical stringing out of the viscid white bacterial slime was seen. Cul¬ 
tures were made by the writer from one of these plants and subsequent 
inoculations from these cultures into healthy plants again gave the dis¬ 
ease. Other wilted plants from the same cage were sent to Washington, 
D. C., and from one of these Bacillus tracheiphilus was obtained and with 
it successful inoculations were made in cucumbers in one of the Depart¬ 
ment greenhouses by Dr. Smith. No signs of wilt occurred in the 3 
other cages in which beetles were placed, or, with one exception, in any 
of the 46 other cages. 
Meanwhile in both fields the wilt was beginning on plants between 
the cages. At first the wilt appeared only on a plant here and there, and 
then gradually extended throughout the two fields until no portion was 
entirely exempt. In the two fields together there were in the neighbor¬ 
hood of 1,200 hills of cucumbers exposed to attack of the beetles. The 
cages in field No. 1 extended approximately a quarter of a mile through 
the field at equal distances and in field No; 2, which was about two-thirds 
as large, they were spaced closer. There was a check plot contiguous to 
each cage. The approximate number of cases on the plants in field 
No. 1 during the three months was 600; in field No. 2 it was 200. No 
counts were made after September 1, owing to the appearance of the 
cucumber mildew (Plasmopora cubensis ). 
In all these cases of wilt in the exposed (uncovered) plants, infection 
was clearly seen to have started from beetle injury. Careful record was 
kept throughout the season of every hill and plant showing wilt, and 
although between the cages the disease was everywhere present the plants 
within the cages were strikingly free from the disease. The plants in 
these 50 cages were examined every day from planting time (June 5-6) 
until September 1. In one cage where beetles were not liberated, wilt 
was noted just starting in the tip leaf of one plant at a point gnawed by 
a beetle. A careful search in this cage disclosed a striped beetle, which 
was summarily disposed of. Microscopical examination and cultures 
from the lower part of the stem failed to disclose any bacteria, showing 
that the wilt in this case could not have come from the soil and must have 
been brought in by the beetle, which probably entered through a crack 
due to warping of the boards. Careful search failed to disclose any 
further beetle injury within the cage, and, after the removal of the beetle 
and the one wilting plant, no further signs of the disease appeared therein 
during the season. With this exception and that of the above-mentioned 
1 cage into which the beetles were .purposely introduced, not a case of 
wilt occurred in any of the 50 cages during the entire season. 
