DISSEMINATION OF BACTERIAL WILT OF CUCURBITS 
[PRELIMINARY NOTE] 
By Frederick V. Rand, 
Assistant Pathologist , Laboratory of Plant Pathology , Bureau of Plant Industry 
In the discussion of his exhaustive studies upon bacterial wilt of 
cucurbits, Dr. Erwin F. Smith 1 makes the following statements relative 
to certain still unsolved portions of the wilt problem: 
Leaf-eating insects, and especially Diabrotica vittata (fig. 55), are, I believe, the 
chief agents in the spread of this disease. They feed readily, and sometimes the 
writer has thought preferably (fig. 7), on wilted leaves which are swarming with this 
organism. In this way their mouth-parts can not fail to become contaminated and 
to serve as carriers of the sticky infection. No other means of dissemination is known 
to the writer, and this is believed to be the common way in which the disease is dis¬ 
tributed. * * * 
Seasonally the disease does not manifest itself until the leaf-eating beetles have 
put in their appearance, and this has led to the suspicion that the organism might 
pass the winter inside the bodies of these hibernating insects {Diabrotica viitata). As 
to this nothing definite is known. 
He has referred to this subject again in his St. Louis address, 2 as 
follows: 
The writer has since proved several diseases to be transmitted by insects, notably 
the wilt of cucurbits, and here the transmission is not purely accidental, but there 
appears to be an adaptation, the striped cucumber beetle {Diabrotica viitata ), chiefly 
responsible for the spread of the disease, being fonder of the diseased parts of the plant 
than of the healthy parts. This acquired taste, for it must be that, works great harm to 
melons, squashes, and cucumbers. Whether the organism winters over in the beetles, 
as I suspect, remains to be determined. Certainly the disease appears in bitten 
places on the leaves very soon after the spring advent of the beetles. 
It was especially with a view toward throwing some light on the mode 
of hibernation of the causal bacteria and of developing some practical 
method of control that the writer undertook to continue the studies upon 
this frequently very destructive disease. Since the study was begun in 
midsummer (July, 1914), the first season’s work consisted largely of 
field observations which covered the territory from eastern Long Island, 
N. Y., and Maryland to Indiana and Wisconsin. Some of the worst 
examples of injury from wilt were found in eastern Long Island, and 
accordingly this locality was selected for the field tests of the following 
season (1915). While further investigations are under way, it appears 
1 Smith, Erwin E. Bacteria in Relation to Plant Diseases, v. 2, p. 215. Washington, D. C., 1911. 
2 -. A conspectus of bacterial diseases of plants. In Ann. Mo. Bot. Gard., v. 2, no. 1/2, p. 390, 
1915- 
Journal of Agricultural Research, 
Dept, of Agriculture, Washington, D. C. 
aw 
(257) 
Vol. V, No. 6 
Nov. 8 , 1915 
G—-64 
