Some Bacterial Diseases oe Plants. 
19 
BACTERIAL BLIGHT OF THE IRISH POTATO, TOMATO, 
EGG PLANT AND TOBACCO. 
Dr. Erwin F. Smith,* Bureau of Plant Industry, U. S. Depart¬ 
ment of Agriculture, has shown that a single species of bacteria, 
Bacillus solanaccarmn (Smith), has the power of producing a 
blight or wilt in a number of plants of the potato family. Among 
the common ones attacked may be mentioned the Irish potato, to¬ 
mato, pepper and egg plant. > In 1903, Dr. F. L. Stevenst and the 
v/riter published an account of what appeared to be a bacterial wilt 
of tobacco in Granville County, North Carolina, to which the name 
Granville Tobacco Wilt was given. The very recent work of Dr. F. 
F. Smith;!: confirms this finding and further shows the cause of the 
disease to be none other than the organism which produces the 
potato blight. Several common weeds, such as the horse nettle, 
jimson weed and ground cherry, are also susceptible to the disease. 
The blight manifests itself in the vines by a sudden wilting, 
either of a part or the whole. The stems usually wither, turn yel¬ 
low and finally black. Young plants appear to contract the disease 
more readily than old ones. By cutting across the affected stem one 
can see the characteristic brown or black, woody tissue in which 
the bacteria are at work. A section across the sick vine just at the 
surface of the ground, or a little below, will usually show, in addi¬ 
tion to the blackened ring, a considerable quantity of a slimy, viscid 
liquid oozing from the blackened parts, especially if squeezed be¬ 
tween the fingers. This is particularly true if the soil is rather 
moist. Microscopic examination shows this liquid to be swarming 
with the bacteria, which cause the trouble. It frequently happens 
in the early stage of the disease that the blackening seen in the 
cross section of the stem will not appear as a continuous ring, but 
only as one or two spots. If the vine is slit lengthwise through 
one of these spots, a blackened streak will usually be found running* 
the whole length of the stem and finally out into the branch or leaf 
which showed the wilt. The germs appear to live in the soil and 
gain entrance to the plant through the root or underground stem, and 
once within the tissue they clog up the water tubes and later on de¬ 
stroy the conducting vessels so that no water can be transported 
from the soil to the branches and leaves and, as a result, we get the 
characteristic wilting. The tubers from sick plants show a distinct 
ring of discolored tissue a short distance from the outside of the 
potato. 
Fungicides are of no value in treating this bacterial disease 
*Bull. 12, Div. Veg. Path., U. S. Dept. Ag. 
tBull. 188, N. C. Expt. Sta. 
JBull. 141, Part II, Bur. Plant Industry, LT. S. Dept. Ag. 
