POTATOES. 261 



chase of a drug-g-ist two ounces of finely pulverized corrosive sub- 

 limate (mercuric bichloride). Empty all of this into two gallons of 

 hot water and allow it to stand over nig-ht, or until apparently dis- 

 solved. Place in the barrel thirteen g-allons of water, then pour in 

 the twc^ gallon solution. Allow this solution to stand in the barrel 

 four or five hours, during which time it is several tiines thoroughly 

 agitated to insure equality of the solution before using. Select as fair 

 seed potatoes as possible, wash off all the old dirt and immerse as 

 many as you can, or wish to treat at one time, in the solution one hour 

 and thirty minutes. At the end of this time turn off the solution into 

 another vessel. The same solution may thus be used a number of 

 times, if wished. After dr5dng, the potatoes may be cut and planted 

 as usual. Plant upon ground that has not previously borne the 

 disease. The potatoes inay be cut before treatment, if wished. 



"Caution: The corrosive subliinate is a strong- poison, and too 

 great care cannot be exercised in its use. The strength of the solu- 

 tion as here recommended, one part in one thousand, is the same as 

 that used in surgery and is not such as to work injury unless taken 

 into the stomach. Great care should be taken in handling- the pure 

 substance, and all treated potatoes should be planted. The solution 

 should not be placed in metallic vessels." 



This treatment has been productive of excellent results at this ex- 

 periment station. As mentioned above, care must be taken to use 

 only wooden or earthen vessels; the corrosive sublimate will destroy 

 metallic vessels. 



Prof. W. J. Green, of the Ohio Experiment Station, states that pota- 

 to scab at that station has been almost wholly prevented b}^ soaking- 

 the seed before planting- for one hour in the Bordeaux mixture. 

 There is much other evidence to show the benefits from using this 

 fungicide for this purpose, and, as it is quite harmless, it is well 

 worthy of trial. At this experiment station its use has been attend- 

 ed with fair results, but these were not equal to those obtained 

 where the corrosive sublimate was used. 



Barnyard manure the cause of scab.— It has been very generally 

 observed that where stable manure is used on potato land, the scab 

 is often most abundant; in other words, its presence seemed to be 

 favorable to the development of the disease. Dr. Thaxter says that 

 he is convinced "that the practice of feeding scabby potatoes to 

 stock is one of the most important measures by which the disease 

 is spread on farms." It is well known that the spores of a great 

 number of fungus diseases pass readily through the stomach and 

 intestines of animals without injury. It is also known that the scab 

 fungus grows readily in manure, and it is altogether probable that 

 these spores pass unharmed through animals fed on scabby pota- 

 toes or scabby beets. The manure that is free from these germs 

 undoubtedly will not necessarily increase the injury from scab 

 fungus. 



CONCLUSIONS. 



(1). Scab of potatoes is caused by a fungus plant working in the 

 surface of the potato. The germs of it are very abundant and live 

 for many years in the soil and also winter over on the potatoes. If 

 these germs are fed to stock, they undoubtedly grow in the manure; 

 and the use of such manure may often be a cause of infection. Al- 



