CONTROI. OF BLACKLEG DISLASL OF THE) POTATO. 215 



untreated portions of the field, accurate comparisons between 

 adjoining portions could not be made. However, an examina- 

 tion of a portion of the extreme western part of the field where 

 the treated seed was known to have been used revealed no dis- 

 eased plants while on the other side of that jjart of the field 

 planted to Cobblers where untreated seed was planted several 

 diseased plants were seen on an equal area. 



On July 19, the limit of the areas upon which treated and 

 initreated seed was used having been accurately determined, 

 approximately one acre of each was critically examined with 

 the following result : 



Seed tubers untreated. Diseased plants per acre 53 



Seed tubers treated (formaldehyde solution). 



Diseased plants per acre . 5 



The Cleveland Company Bxperiment. 



On the Cleveland Company farm disinfection was performed 

 by means of formaldehyde gas and two varieties of potatoes 

 were used. These were the Irish Cobblers and the White Rose, 

 sometimes called the Ensign Bagley. 



The field of Irish Cobblers consisted of about 20 acres, the 

 larger portion of the seed for which was treated. This field 

 was visited the first time and quite carefully inspected on July 

 -19. At least some portion of nearly every acre was critically 

 examined, but in no case could hills affected by blackleg be 

 found, either where the treated or untreated seed was used. 

 This indicated that the seed was originally free from the dis- 

 ease and in this case treatment was unnecessary so far as black- 

 leg was concerned. 



The White Rose seed was known to' be considerably affected 

 with blackleg and it was with this seed that the real test was 

 made. This portion of the field consisted of about 10 acres of 

 which all but about one acre was planted with disinfected seed. 

 After being satisfied that the plots selected were representative 

 of the different parts of the field as a whole with regards 

 amount of blackleg about one-tenth acre each, of plants from 

 treated and untreated seed, was carefully examined. The re- 

 sults obtained were as follows : 



