132 JOURNAL OF THE ROYAL HORTICULTURAL SOCIETY. 
THE STRAWBERRY MILDEW. 
{S2)hcerotJieca Humuli (DC.) Burr.) 
By Eknest S. Salmon, F.L.S. 
DuEiNG the past season of 1900 several cases of crops of Strawberries 
completely ruined by this fungus have come under my observation, and 
reports have also reached me of the occurrence of this disease from many 
widely separated localities. The severity of the disease — causing in the 
worst cases the Strawberry fruit to be at once ruined for the market— and 
its economic importance demand that serious attention should be paid to 
the subject. 
Historical. — It has been known for some time that Strawberries are 
liable to be attacked by a " mildew," although it appears that — at any 
rate in England — it is only quite lately that the disease has shown signs 
of causing destruction on a large scale. Apparently the first mention of 
the disease appears in the Gardeners' Clironicle for 1854, where Berkeley 
(1) reported that a crop of Strawberries (Cuthill's Black Prince) had been 
entirely destroyed by a mildew. This fungus, from the description given, 
was evidently Sphcerotlieca Htimuli in its conidial stage, although 
Berkeley referred it to " Oidium Balsamii, the Turnip Mildew," the 
conidial stage of an Erysiphe. 
In the Garden for 1885 J. Cornhill (2) reported the occurrence of a 
"mildew" in Strawberry pits, and recorded the successful treatment of 
the plants with sulphide of potassium. 
In 1886 the disease in America attracted the attention of Professor 
J. C. Arthur (8), who identified the fungus as Sphcerotheca Castagnei, 
Lev. 
In 1892 Humphrey (4) recorded the occurrence of the " Powdery 
Mildew of the Strawberry " on plants grown at the Massachusetts 
Agricultural College. In this case the fungus confined its attacks to the 
leaves. Lodeman (5), in " The Spraying of Plants " (1896), notes the 
occurrence of S. Castagnei on the berries and leaves of the Strawberry, 
but states that " the disease is rarely serious." 
In the Journal of the Board of Agriculture for September 1898 (6) 
an account is given of a fungous disease which is stated to have seriously 
attacked English Strawberries during the season of 1898. In this account 
the fungus is identified as SplicBrotlieca pannosa, the common Rose 
Mildew. There is no doubt, however, that a mistake in the identification 
was made, and that the fungus under observation was really Sphcerotheca 
Humuli (=S. Castagnei, Lev., in part). 
Description of the Disease. — In the first stages of attack the fungus 
affects the leaves, causing them to curl at the margin, and so expose 
their under- surfaces, giving an appearance as though the plants were 
suffering from want of water. On these diseased leaves the fungus is 
found in its conidial stage, and is almost entirely confined to the under- 
