92 
Journal of Agricultural Research 
Vol. VIII, No. 3 
After certain preliminary experiments and with the realization that no 
control measures would be of much practical use unless they were effec¬ 
tive in the hands of the potato growers themselves, it was decided to 
ask the cooperation of those interested in the work in order to test these 
control measures on a large scale under actual field conditions. In 
1911, cooperative experiments were conducted by eight practical potato 
growers in three separate towns. On the eight different farms approxi¬ 
mately 300 acres of potatoes were under experiment. Collectively these 
gentlemen selected and disinfected seed tubers sufficient to plant 142 
acres. Formaldehyde solution was used for 88 acres and formaldehyde 
gas for 54 acres. Detailed statements of the methods' used and of the 
results secured from these experiments have been previously published 
(24)* 
The experimental fields were carefully watched by the owners for the 
appearance of diseased plants. The writer visited some of the farms 
several times and during the first and third weeks in July made a thorough 
examination of each experimental field, counting each time the number 
of diseased plants upon representative areas. 
The question might naturally be raised that only two careful counts 
of diseased plants on each part of the experimental fields during the 
season would not accurately show the actual amount of blackleg on 
them, for, as has already been pointed out, the time of the greatest evi¬ 
dence of the disease on a given field may be materially influenced by 
seasonal climatic conditions. That there may be something to this ob¬ 
jection is freely granted; but the writer maintains that it in no way 
influences the relative number of diseased plants on the different plots 
at the time the counts were made, and this seems to be a fair way of 
judging the efficiency of the different methods of treatment employed. 
Moreover, if it were to appear at all on the plots planted at the same 
time with selected and treated tubers, there seems to be no valid reason 
why blackleg should not show up equally early in the season as on the 
check plots planted with unselected and untreated tubers from the same 
lots or bins. As a matter of fact, the times at which these counts were 
made were selected because they coincided with the period at which 
blackleg was most in evidence in surrounding fields that season. Also, 
as has already been stated, other visits made to the fields at various 
times during the season and the observations made by the owners of 
the fields themselves furnish plenty of data to confirm the conclusions 
derived from the counts of diseased plants. 
Taken as a whole, the results of the cooperative experiments were 
sufficiently clear-cut and conclusive to indicate that the preventive meas¬ 
ures outlined are exceedingly efficient if properly carried out. In fact, 
the uniformity of the results was surprising, since so many individuals, 
including the men who were employed to cut the seed, were respon¬ 
sible for them. In every case where both carefully selected and treated 
