105 
his seed potatoes are absolutely free from scab and it is by far 
the safest way to first disinfect all seed potatoes whether scabby 
or not so as to kill the disease before introducing it into the 
ground, where once introduced, it will remain for years to come. 
Badly infested potatoes are readily detected, but at times the in- 
festation is so slight that it is difficult to detect it even with a 
good microscope. Clean culture is another agent for the pre- 
vention of scab and on ranches where potatoes are grown, the 
stock, especially hogs, should not be fed the potato peelings, es- 
pecially from potatoes brought from places where the scab is 
known to exist. For those who desire to free their potatoes from 
this disease and prevent its introduction into the fields the follow- 
ing remedies can be used : 
Remedies for Potato Scab. 
For small lots use: 
1 pint Formaldehyde, 
30 gallons water. 
Put solution in half barrels and soak the potatoes for two 
hours. This should be done shortly before planting and before 
the potatoes are cut for seed. 
For large lots use for a tight room of about 1,000 cubic feet 
the following: 
23 ounces of Potassium Permanganate, 
3 pints of Formaldehyde. 
After stacking the potatoes in bags allowing plenty of space 
for the fumes to pass all around each sack — this can be done 
by placing 2x4 scantlings between each layer of sacks — the Per- 
manganate of Potassium should be spread in a thin layer on 
the bottom of the vessel, then the Formaldehyde poured in and 
stirred quickly and then vacate the building and see to it that the 
door is thoroughly tight. The potatoes should be subjected to 
the fumes for at least 24 hours. Potatoes after treatment should 
not be put into old sacks or vessels which are liable to have 
spores of the scab, as all the work done will be without avail. 
Summary. 
Land which has produced scabby potatoes the previous year 
should not be planted for one or two years with potatoes. 
All seed should be carefully treated as recommended above. 
Scabby potatoes or portions thereof should never be fed to 
stock. 
Barnyard manure if produced where scabby potatoes have been 
fed to stock should not be used as fertilizer for potato field. 
When once a field becomes infested with scab, rotation of crops 
other than root crops, is absolutely necessary. This requires 
from one to three years according to extent of infestation. 
Edward M. Ehrhorn, 
Superintendent of Entomology. 
