Porarors 1387 
BLIGHT 
Taken altogether, the most serious foe to the potato is the blight. 
It is so insidious in its attacks that if preventive measures are not 
employed early in the season it will often ruin a potato crop in 
twenty-four hours. The late blight is the one most in evidence 
and most destructive. It is peculiarly a wet weather disease, the 
spores of which, so far as is known, live over winter only in the 
old tubers. When such infested tubers are planted and the earth 
becomes warm and moist, these spores multiply and burst from 
their cells, so that the soil literally swarms with them. Many, of 
course, die; some find their way to the surface. Often, when the 
plants are five or six inches high, a heavy rain will beat them down 
to the earth where they come in contact with the blight spores. 
If the weather continues wet, these multiply and penetrate the 
leaf. Later they spread to other leaves and live on the leaf tissues. 
When weather conditions are favorable, i. e., wet, they increase at 
an enormous rate, and so destructive are they that a field will often 
turn black in a day. If the wet is excessive, these spores are 
washed from the tops to the ground, and so to the tubers again, 
and rot often follows — always infection. Here is another reason 
for deep planting. Tubers are less exposed to the spores and be- 
ing deeper and cooler in the spring, fewer spores germinate and 
come to the surface. There is no cure after the spores are estab- 
lished, but it can be prevented by what is known as the bordeaux 
mixture, viz., 5 pounds of copper sulphate (blue vitriol), 5 pounds 
of lime and 50 gallons of water. If this is thoroughly applied 
early, before the leaves are contaminated, it copperplates them, as 
it were, and the blight spores die because they can not gain an 
entrance. It must, therefore, be applied in season, thoroughly, so 
as to protect the whole plant, and often enough to cover the new 
growth. Sometimes one spraying before the spores come from 
the ground has been sufficient. Usually three give excellent re- 
turns. Again, five are even more profitable. Much depends on 
the season, as well as on the time and thoroughness of the work. 
There is no question as to its practicability, in proof of which 
I call attention to Bulletins No. 323 and 349 of the New York 
State Experiment ‘Station, which may be had for the asking. 
Briefly stated, the facts are these: For seven years the station 
