286 
Journal of Agricultural Research 
Vol. XXIII, No. 4 
Pethybridge ( 8 ) observed the disease in Ireland and gave it the name 
of skinspot. Exposed cut surfaces of the pustules, when subjected to a 
moist atmosphere, produced a strong growth of a fungus identified as 
Spicaria solani Hart. He states that— 
no cultures or infection experiments have been made in connection with this “ skin- 
spot” and, therefore, it can only provisionally be regarded as caused by Spicaria. 
. Milbum and Bessey (5, p. 90-91) attributed an apparently identical dis¬ 
ease which they called “blotches” or “pimples” to an organism referred 
to by them as Spicaria nivea . They obtained this fungus in every cul¬ 
ture made by planting the inside of the pimples but failed to reproduce 
the disease by inoculation of healthy tubers with it. 
A few years later Giissow (2), who previously worked with Carruthers, 
discarded the fungus theory of skinspot altogether and attributed it to 
unfavorable storage conditions which interfere with normal respiration 
of the resting tubers and result in the production of the symptoms of 
skinspot. He drew his conclusion solely from the observation that this 
trouble invariably occurred in badly ventilated storage cellars but reports 
no experimental work along this line. 
About the same time O’Brien (6), describing Rhizoctonia injuries to 
potatoes in Scotland, included in his illustrations a photograph (6, PI. V) 
which in all its characteristic features may be regarded as representative 
of skinspot. The author, however, uses it as an illustration of an injury 
caused by Rhizoctonia crocorum (Pers.) DC. and states in the text: 
If such an affected tuber be moistened with water, numerous small blackish areas 
can generally be seen immediately below the surface which cause the skin of the 
potato to be elevated at such points. These areas are sclerotia. 
Apparently without any connection with the English work on skin¬ 
spot, Wollenweber (jo) recently published in Germany a pamphlet on 
potato scab in which he describes a disease named by him “pustelfaule” 
and illustrates it with a photograph of the affected potato tuber which 
leaves no doubt as to the identity of this trouble with the English skin¬ 
spot. This “pustelfaule,” according to Wollenweber, is caused by 
Phoma eupyrena Sacc. He observed the mycelium of this fungus in the 
diseased tissues and obtained the organism in the majority of his isolation 
cultures. Further, upon inoculation of healthy tubers in needle pricks 
he produced “similar spots.” He states very clearly that Spongospora 
was altogether absent in the diseased tissues. 
The most extensive and quite recent study of skinspot was made by 
Owen (7). While using for the isolation work only those spots which 
had the skin unbroken, the author obtained in every culture a similar 
fungus which is described and named Oospora pustulans. In sections of 
the spots, the fine mycelium of this fungus, it is said, is plainly seen 
among the dead cells of the potato tissue. The hyphae are very numer¬ 
ous and for the most part hyaline early in April, when the fungus appears 
to be most vigorous, but later in the season they are very few and mostly 
brown. Skinspot, according to Owen, is a disease which develops in stor¬ 
age and is not usually visible until the early spring. 
In concluding this bibliographical review it may be of interest to men¬ 
tion that the same disease has been locally known in British Columbia 
as pit Fusarium. The name itself explains its raison d’etre—the disease 
is commonly found in pits and is believed by some to be caused by a species 
of Fusarium, presumably Fusarium radicicola. This erroneous opinion 
was based on a certain external similarity of skinspot pustules with some 
initial stages of the lenticel infection with the blackrot fungus as figured 
