oct. 3o, 1916 Spongospora subterranea and Phoma tuberosa 
241 
which occur around some of the sori, and the importance of the part 
played in this connection by the wound parasites which enter through 
the injury caused by 5 . subterranea . In view of the fact that the rot was 
first found associated with 5 . subterranea and is most common on pota¬ 
toes infected with the disease caused by that organism, it seems desirable 
to call it “powdery-scab dryrot.” 
HISTORY AND DISTRIBUTION 
Powdery-scab dryrot was first observed by the senior writer on pota¬ 
toes infected with Spongospora subterranea collected in New Brunswick, 
Canada, in the fall of 1913, and held in storage in Washington, D. C. 
Later it was collected in Aroostook County, Me., and in the infected 
section of New York State. 
Although first found in America, the rot is not confined to this coun¬ 
try. A typical case of it was found in a shipment from Ireland by 
Mr. H. B. Shaw, Pathological Inspector of the Port of New York. About 
a bushel of the infected tubers collected and sent by Mr. Shaw to one 
of the writers for examination as to the causal organism showed pro¬ 
nounced discoloration and shrinkage and later on a rot. In the fall of 
1913 three i-barrel sacks were taken at the port of New York from a 
shipment of potatoes from the Netherlands which showed a considerable 
percentage of infection by Spongospora subterranea and was shipped to 
Washington, where the diseased tubers were separated from the healthy 
ones and both lots placed in storage. When these were examined two 
months later, 21 per cent showed shrinkage and rotten spots. 
A dryrot has been found on infected tubers collected in Chile, South 
America, but in this case the rot was not marked, as in the case of the 
European tubers, and may well have been accentuated by the long 
period of transit under poor storage conditions. Be this as it may, 
however, it is perfectly clear that to some extent at least a dryrot follow¬ 
ing infection by Spongospora subterranea develops on potatoes, no matter 
where they are grown. 
PREVALENCE) OP AND LOSSES FROM POWDERY-SCAB DRYROT 
Powdery-scab dryrot develops on potatoes after they have been held 
in storage for some time. It is accelerated by poor storage conditions, 
but even in good storage from 30 to 75 per cent of the tubers become 
partially or wholly decayed and consequently worthless for seed or table 
use. Morse (9) refers very briefly to a rot connected with Spongospora 
subterranea which is doubtless the same as the one under consideration 
here. This rot, he states, develops on potatoes held in good storage 
and is hastened when infected potatoes are subjected to ordinary room 
temperature for a few days. 
