Jan. is, 1917 
Blackleg Disease of Potato 
93 
seed tubers were used the disease was absolutely eliminated. In two 
instances this occurred on fields planted the second year in succession, 
in which considerable blackleg occurred the year before, and also 
appeared upon the check plots used in the experiment. Also in every 
case where either disinfection or selection was practiced alone and proper 
check plots were planted for comparison, the amount of blackleg was 
materially reduced, except on one field where small inferior tubers were 
purposely sorted out and planted after first being disinfected with 
formaldehyde solution. 
An analysis of the data furnished by the experiments did not lead to 
any very definite conclusions as to the relative value of selection of sound, 
perfect seed potatoes for planting as compared with disinfection with 
formaldehyde alone. There is no doubt that both are necessary. The 
writer believes that careful selection of seed tubers and rejection for 
planting all that are in any way cracked, bruised, discolored, or decayed 
is absolutely essential, and no amount of disinfection with the present 
known methods can be relied upon to take the place of it. On the other 
hand, the formaldehyde treatment appears to be equally essential and 
must be practiced to supplement selection of seed. No one familiar with 
bacterial softrots of vegetables would assume or suggest that formalde¬ 
hyde solution or gas could be relied upon to disinfect entirely or even 
approximately a tuber the interior of which is partially decayed. The 
writer has never maintained that this could be done, and it would be 
unnecessary to refer to it or emphasize the point were it not for the fact 
that in some instances it has been assumed that he did recommend 
simply seed disinfection with formaldehyde for the control of the disease. 
Unfortunately, the way the experiments worked out there was no 
opportunity to compare on the same field the relative efficiency of formal¬ 
dehyde gas and solution. In every case where formaldehyde gas was 
used the results were less efficient than those where formaldehyde solu¬ 
tion was used. For this and other reasons the gas treatment is not 
recommended for general use. 
Numerous other cases have come to the writer's attention where careful 
selection of sound, healthy seed tubers, followed by disinfection with 
formaldehyde has either eliminated or largely reduced the amount of 
blackleg in the resulting crop, but only one of these will be mentioned. 
In* 1911 the Maine Agricultural Experiment Station purchased two 
lots of Irish Cobbler potatoes for planting at Highmoor Farm in the 
central part of the State. These were disinfected with formaldehyde, 
but no special care was used in selection before planting. In both cases 
quite a percentage of the resulting plants were attacked by blackleg. 
The following season the farm superintendent personally saw that the 
writer's recommendations relative to seed selection and disinfection 
were rigidly carried out. A clean crop resulted, and since then no 
blackleg has been observed on this farm. 
