226 MAINi; AGRICULTURAI, EJXPSRIM^NT STATION. I9II. 



Method op Eliminating Blacki^e^g from St^o Potatoe;s. 



From the foregoing discussion it is evident that if seed pota- 

 toes are carefully selected so that only those which are abso- 

 lutely sound and perfect are used for seed purposes and these 

 treated with formaldehyde that the disease can be eliminated in 

 from one to two year's time. 



For home use it is strongly recommended that only formalde- 

 hyde solution be employed. This consists of one pint of. 40 per 

 cent, formaldehyde in 30 gallons of water in which the potatoes 

 should be soaked 2 hours and then spread out on a clean place 

 to dry, preferably in the sun. Exposure to sunlight will also 

 assist m destroying the bacteria causing the disease and tend 

 to hasten germination. 



It is only advised that the formaldehyde gas method be used 

 by the large seed dealers who must pick up a considerable 

 amount of their stock under conditions which preclude a knowl- 

 edge of the amount of disease which appeared on the fields 

 where the stock was grown. In such cases a special disinfecting 

 room should be provided and fitted up with provisions made for 

 the proper regulation of the temperature and moisture condi- 

 tions during treatment. This work should be placed in the 

 hands of a competent man who thoroughly understands each 

 step and detail of the process. All seed tubers which are not 

 known to be free from the germs of blackleg and potato scab 

 should be disinfected in this way before being shipped.* 



There seems to be a general misapprehension among potato 

 growers as to the cost and amount of labor involved in the liquid 

 method of treatment. Mr. Donaldson, following suggestions 

 furnished him by the writer, worked out a satisfactory method 

 adapted to his conditions whereby he was enabled to treat 260 

 barrels of seed potatoes for a total cost of about $10.00 for 

 labor and formaldehyde, a little less than 4c. per barrel or about 

 20c. for each acre planted. The following is Mr. Donaldson's 

 account of how this was done : 



* For a detailed description of the method of disinfecting seed poto- 

 toes with formaldehyde gas generated by means of potassium per- 

 manganate the reader is referred to page 324 of Bulletin 174, or to page 9 

 of Miscellaneous Publication No. 375 of this Station. 



