CONTROIv OF BI^ACKLEG DISE^ASS OF THE POTATO. 219 



When examined on July 7 and 20 there was a large amount 

 of blackleg on this field, fully 20 per cent of the hills either 

 failed to grow or the plants had been destroyed by the disease. 



Discussion of Rfsults. 



Effectiveness of the treatment: Taken as a whole the results 

 of the cooperative experiments are sufiiciently clear-cut and 

 conclusive to indicate that the preventative measures outlined 

 are exceedingly efficient. In fact the uniformity of the results 

 is surprising when it is remembered that so many individuals, 

 including the men employed to cut the seed, were responsible 

 for them. It will be noted that in every case where both 

 selected and treated seed was used the disease was absolutely 

 eliminated and in every case where either selection or disinfec- 

 tion was practiced alone and proper check plots planted for 

 comparison the amount of blackleg was materially reduced, 

 except where the small, inferior seed was used in the Porter 

 experiment. However, it should be remembered that the check 

 plot here is the seed just as it came from the bin, and that the 

 small seed in question represents practically the poorest grade 

 that co'uld be sorted from it. Had Mr. Porter planted an 

 untreated check plot of this small, inferior seed also it doubt- 

 less would have carried considerably more disease than the 

 treated plot. The case would have been similar to the one 

 where Mr. Donaldson compared plots planted with treated 

 and untreated seed which was bruised and otherwise imperfect. 



While not a part of the experiments here recorded certain 

 observations made on the John Watson farm in Houlton dur- 

 ing the past five years have a bearing on this subject. In 1907 

 in connection with certain experiments then being carried on 

 a special disinfecting room was constructed on this farm in 

 which to treat seed potatoes for scab.* Every year since that 

 time all the seed used on this farm has been disinfected with 

 formaldehyde gas, primarily as a protection against scab. Eoth 

 Green Mountains and Irish Cobblers have been planted, the 

 latter entirely during the last 2 years. A part of the time the 

 seed tubers used were picked up from various sources without 

 knowledge of the conditions under which they were grown. 



Bill. Me. Exp. Sta. 140: 304-314 (1907). 



