28 MAINE AGRICULTURAL EXPERIMENT STATION. 



Use for seed only stock that is known to be free from con- 

 tamination with powdery scab. Remove all tubers which are 

 bruised, cracked or show evidence of decay or disease of any 

 kind. Soak this sorted and selected seed for two hours in a 

 solution of one pint of 40 per cent formaldehyde in 30 gallons 

 of water, or one and one-half hours in a solution consisting of 

 four ounces of corrosive sublimate in 30 gallons of water. Have 

 two or three knives for each cutter and when not in use immerse 

 the blades in a strong solution of formaldehyde. When cutting 

 seed reject every tuber which shows any discoloration of the 

 interior. At once drop the knife used in cutting the discolored 

 tuber into the strong formaldehyde and use one of the other 

 knives until another suspicious potato is cut. Use care that the 

 disinfected seed does not come in contact with barrels, baskets, 

 planters, etc., which have been used for diseased seed. 



It is recommended that seed tubers be thoroughly dusted with 

 sulphur as soon as they are cut, or before the surfaces have 

 become dry. 



No exact data are available as to how long the germs of 

 powdery scab remain in the soil after once introduced, but the 

 Station has secured information that indicates that this is a 

 matter of several years, at least. Hence, land known to be 

 infected should be kept in other crops as long as possible. If the 

 infected area is large it would be best to test a small patch in 

 the worst infected section by first planting it with clean, disin- 

 fected seed a year in advance before risking the chance of loss 

 of seed and crop on the whole field. 



Methods of Disinfection. 

 Many inquiries have been addressed to the Station asking for 

 information as to the best methods for disinfecting potato storage 

 houses, implements or containers which may have become con- 

 taminated with the germs of powdery scab. The notion that 

 the disease may be spread by means of articles which have come 

 in contact with affected potatoes appears to be well founded. 

 No doubt, if it could be traced, it would be found that some of 

 the powdery scab in Maine came from the purchase of second- 

 hand sacks previously used for imported potatoes. Likewise it 

 is evident that only a relatively few barrels of affected tubers 

 in a storage bin might so infect the bin and other parts of the 



