4 BULLETIN 81, U. S. DEPARTMENT OF AGRICULTURE. 
moisture. Silver scurf has been known in Europe for many years, 
but it was not noticed in America, except in one instance (by Dr. 
Clinton in Connecticut in 1907), until 1912, when it appeared on 
potatoes from nearly every State from Maine to Florida and westward 
to Wisconsin. It is now thoroughly established here and, though a 
minor trouble, adds another to the agencies which disfigure potatoes. 
There is evidence to justify the fear that silver scurf may become ! 
more injurious in the United States than it has been in Europe. 1 
Other potato parasites have come from the far West or from the , 
South. The migration of the Colorado potato beetle from the Rocky 
Mountain region is well known. Two diseases, the southern bacterial 
brown-rot and the Fusarium wilt, appear to be of southern, possibly 
tropical, origin, though this is not fully established. 
THE WART DISEASE. 
Potato wart, black scab, or canker is a disease which transforms 
the tubers into irregular, warty excrescences, at first greenish or 
white, then black and decaying. It is a fungous disease (Synclii- j 
trium endobioticum) of comparatively recent discovery, first described 
from Hungary hi IS 96 and found in England about 1902 and in 
Westphalia in German}' in 1908. It has spread considerably during 
the past decade until it seems firmly established in England and 
Scotland, has gained a foothold on the coast of Ireland, and has 
crossed the Atlantic to Newfoundland, where Dr. H. T. Giissow, 
Dominion botanist, discovered it in 1909. Fortunately, it has not 
yet been found on potatoes grown in the United States. 
Most authorities consider it one of the very serious diseases of the 
potato, as it converts the tuber into an ugly, irregular, and utterly 
worthless article, and when established hi the soil will attack the 
succeeding crops and prevent the growing of potatoes hi such in- 
fected soil for many years. 
The countries where the wart occurs have for the most part taken 
vigorous measures to suppress it, and other nations have endeavored 
to prevent its introduction. It was primarily on account of this 
trouble that the Secretary of Agriculture issued Quarantine Order 
No. 3, September 20, 1912, prohibiting the entry of potatoes into the 
United States from Newfoundland, the islands of St. Pierre and 
Miquelon, the United Kingdom (including England, Scotland, Wales, 
and Ireland), Germany, and Austria-Hungary, although powdery 
scab was also taken into consideration at that time. 2 
1 For further details, see the paper in Circular 127, Bureau of Plant Industry, U. S. Department of 
Agriculture, by I. E. Melhus, entitled "Silver scurf, a disease of the potato." Obtainable from the Super- 
intendent of Documents, Government Printing Office, for 5 cents. 
2 Fcr further information on the wart disease, see Farmers' Bulletin 489. 
