coNTROi. OF bl,acki,e;g dise;ase: of the; potato. 225 



their seed with formaldehyde sohition are advised to try it in a 

 small way experimentally. If successful it could be done just 

 before planting, the seed being soaked and dried in the sun as 

 fast as needed for planting. It would not be practical to attempt 

 to disinfect cut seed by the gas process. 



Vigor of Pi^ants as Afffctfd by Formai,dfhydf 



DiSINFEjCTlON. 



The writer has used "formaldehyde experimentally as a dis- 

 infectant for seed potatoes nearly every year for the past ten 

 years and before the present season has never observed any 

 marked difference in the germinating qualities or rapidity of 

 growth of plants from treated and untreated seed. If short 

 sprouts have started at the time of treatment these are partly 

 or wholly killed back, hence on theoretical considerations one 

 would assume that the untreated tubers would have a slight 

 advantage. 



In the Parsons, Porter and Donaldson experiments the plants 

 from the treated seed tubers germinated first and were plainly 

 stronger and more vigorous during the early part of the season. 

 This was especially marked on the Donaldson farm. Here both 

 the poor and the good seed which was treated gave more vig- 

 orous plants than the portion of the same lot of tubers which 

 was not treated. This was so marked that it could be detected 

 some distance from the field even up to the middle of July. 

 There was nothing to indicate that the formaldehyde produced a 

 stimulating effect similar to etherization, but rather that the 

 result was due to freeing the seed pieces from bacteria and fungi 

 which might attack them and set up an early decay. In oppo- 

 sition to this hypothesis it is hard to see how these would be 

 likely to carry, aside from the germs of the blackleg disease, 

 any bacteria or spores of fungi which would not exist in abun- 

 dance in the soil in which they were planted. However, when the 

 weaker plants from the untreated seed were dug up in July the 

 seed pieces were usually decayed while those from the more 

 vigorous plants where the treated tubers were used were quite 

 free from decay at this time. 



