POWDERY SCAB OF POTATOES. 9 
might make it a serious enemy of the potato in the United States, at 
least as bad as the common scab caused by Oospora scabies, and prob- 
ably worse. 
The effect of the milder form of Spongospora upon the tuber resem- 
bles that of the common scab in that it disfigures the potato and 
thereby reduces the market price, even though the food value may 
not be materially impaired. It differs from Oospora scab in that the 
advanced or cankerous stage ruins the tuber for both table and seed 
purposes. 
In this connection it should be remembered that any kind of scab 
or other injury that mars or defaces the potato tuber is a more serious 
handicap in the American markets than in those of some European 
countries, due to the fact that consumers abroad offer fewer objec- 
tions to scabby potatoes than consumers in the United States, There 
is even a belief prevalent abroad that scabbiness is an indication of 
superior quality. In the United States, when potatoes are put on 
the market, scabby potatoes must be sorted out, and therefore are 
of no use except for stock feed or the manufacture of starch. In 
Maine the price of scabby potatoes in the autumn of 1913 was 50 
cents per barrel, while clean stock brought $1.50 per barrel. In the 
country as a whole, hundreds of thousands of bushels of potatoes are 
left in the fields because they are too scabby to market, There are 
frequent instances in the New York markets, according to potato 
dealers, where carload consignments are rejected because of the 
presence of numerous scabby potatoes. When the soil becomes in- 
fested with scab its value as potato land materially depreciates. This 
is especially true in sections where potatoes constitute the chief crop. 
The character and relationship of the parasite should also be 
taken into consideration in judging the danger which powdery scab 
presents. This is a case of dealing with a slime mold, a relative of 
the serious disease of cabbage, turnips, and related plants, known as 
clubroot. 
If powdery scab should prove no more troublesome in the United 
States than it has been up to the present in Europe, it would be rated 
as a disease of secondary importance as compared with late-blight or 
with Fusarium wilt. But there are reasons for fearing that it may 
become more prevalent here. It seems to be a fact that common scab 
is less troublesome in Europe than in America, and the same condition 
might be the case with powdery scab. It quite often occurs that 
introduced parasites are more destructive in a new habitat than in 
their native environment. Likewise, it is not impossible that Spon- 
gospora may find the American varieties of potatoes more sus- 
ceptible than the European sorts. There is also no means of pre- 
dicting the behavior of Spongospora under the varied climatic and 
soil conditions of the several States. The parasite has only recently 
