218 
Journal of Agricultural Research 
Vol. VII, No. 5 
cent of the crop was found to be infected with Spongospora subterranea. 
In the case of two barrels of tubers selected at random from a 15-acre 
field near Caribou that had been planted to potatoes in 1914 after 
they had been picked by laborers and the healthy and infected tubers 
separated, 68 per cent by weight were found to be infected with the 
disease. The field in question was no exception, so far as the prevalence 
of the disease is concerned. Again, in the case of 117 hills which were 
dug at the same time by hand at random over 2 acres of this field and the 
infected and healthy tubers separated, 63 per cent of the progeny was 
infected and only two hills were free from the disease. It is needless 
to say that the crop thus infected could not be marketed for table use; 
and as the only way to turn it into money was to sell it for starch pur¬ 
poses, the grower sustained considerable loss, potatoes for starch usually 
selling for less than 15 cents per bushel. 
The question as to how long land infected with Spongospora subterranea 
will remain contaminated is an interesting one. Pethybridge (12, p. 352), 
of Ireland, holds that it will remain infected for three years. In the 
case of two fields which, after growing a crop of potatoes, were in 
oats for one year and in meadow for four years and were planted to 
potatoes in 1914, over 50 per cent of the tubers were infected with 
5 . subterranea , although there was every assurance that the seed used 
was flee from the disease. Numerous other cases indicate that the 
disease can live in the soil for more than three years, and from facts at 
hand the writers believe that it can live for at least five years and proba¬ 
bly much longer. It is evident, therefore, that when a piece of land 
once becomes infected, a very long rotation is necessary to rid it of 
infection and its value for growing potatoes is materially diminished. 
The facts that Spongospora subterranea can live in the soil for at least 
five years and that it is prevalent in certain sections of Maine raise the 
question as to what length of time it has existed in this country. Its 
distribution in three counties of Maine, extending from the southern 
coast to the northern boundary, and in areas scattered over thousands 
of acres in the State naturally required some time; and consequently it 
must have existed in this country for a considerable period. 
Not only is the disease widely distributed in Maine but also in the 
adjoining Province of New Brunswick, the St. John River Valley being 
quite generally infected, and in Prince Edward Island, which has long 
been settled. As the earlier settlers of northern Maine came from parts 
of New England farther south and up the St. John River Valley and as 
more than 60 per cent of the population of the State is of New Brunswick 
origin it is evident that over half the inhabitants of Maine came from a 
section generally infected with Spongospora subterranea . In view of this 
fact and that the disease exists in this country and in Canada, it seems 
reasonable to believe that it has existed in the infected sections of Maine 
for at least 15 years. 4 
