CONTROL OF BIvACKIvEiG DISElASE OF THE) POTATO. 209 



There was little variation in soil conditions. According to 

 the map of the Soil Survey of the Caribou Area, Maine,* Mr. 

 Donaldson's field consisted entirely of the Caribou loam Avhich 

 is the type of the best Aroostook potato soil. This was the 

 only field which was included in the soil survey but so far as 

 could be determined the soil on all the other experimental fields 

 was either identical or conformed very closely to this type. In 

 each case the fields were well cared for, were well drained, and 

 consisted of either level or slightly rolling land. 



Details, of the; Coopfrativf Expfrimfnts. 

 The Parsons B^'periment. 



Mr. Parsons' field consisted of about ii acres of sod land. 

 The portions where the treated seed was used comprised 7 rows 

 near the East side and 15 rows near the middle, running en- 

 tirely across the field, and together constituting about one and 

 one-tenth acres. The seed was treated by soaking in formalde- 

 hyde solution and was carefully sorted when cut, Mr. Parsons 

 looking after this himself. Untreated but selected seed was 

 used on the remainder of the field. None was planted without 

 selection. 



The field was visited on July 5 but the plants were not suf- 

 ficiently advanced to show the maximum amount of blackleg. 

 Hence no records were made at this time except to note that 

 the disease was beginning to appear on the untreated portions. 

 On July 17 approximately one-half acre of each on adjoining 

 portions of the treated and untreated plots was carefully ex- 

 amined for blackleg with the following results.** 



* Weston, H. L. and Rowe, R. W., Advance Sheets Field Operations 

 of the Bureau of Soils, 1908, Washington, 1910. 



** On each farm care was taken to select portions of the plots of 

 equal size and in every way uniform except as for seed treatment upon 

 which to make the records. Of necessity the area of tlie portions so 

 selected varied on the different farms. For convenience in comparison 

 the records made have been reduced to numbers of diseased plants per 

 acre. A superficial examination of the field as a whole or certain 

 portions of it was made in each case to ascertain if the portions selected 

 for detailed examination represented average condinons. Moreover 

 with few exceptions the owner or his personal representative was pres- 

 ent and assisted at each examination of the experimental fields. In 

 each case a preliminary draft of the write-up of the different experi- 

 ments was submitted to the owner of the field for his approval before 

 it was incorporated in this report. 



