150 FUNGOID PESTS OF CULTIVATED PLANTS. 



In this stage it is more likely to submit to treatment by fungicides- 

 than in the more mature or resting condition. 



Sacc. Syll. iv. 988 ; Sacc. F. Ital. t. 1006 ; Mass. PI Dis. 107. 



Kipening fruits are liable to attack from Oidium Balsami, already 

 described (ante, p. 84). 



STRAWBERRY-LEAF BLIGHT. 

 Sphcerella Fragaria (Sacc.), PI. XII. fig. 42. 



When a spot first appears on a young leaf it is brownish or reddish, 

 then becomes circular with a dead white centre (3-6 mm.) and broad 

 purple border. Subsequently conidia are produced as already described 

 (Eamularia Tidasnei], which for some time are produced in succession 

 from the same threads. If these conidia fall on a fresh leaf surface they 

 germinate in a few hours. In the latter part of the season the mycelium 

 becomes compacted into sclerotia, which are capable of germinating and 

 producing a crop of conidia in the spring. 



Perithecia are developed in late autumn, but are not matured until 

 the spring, upon the white centre of old spots. Asci are produced within 

 these perithecia, each containing eight oblong colourless two-celled 

 sporidia (15 x3-4 p). 



The fungus passes the winter under three forms : (1) as mycelium in 

 the leaves, (2) as sclerotia developed from the mycelium, (3) as ascospores 

 produced in the perithecia. 



The remedies suggested are a solution of sulphide of potassium one 

 ounce to eight gallons of water. Also the copper solutions. Burning of 

 il spotted leaves which may carry the disease over to the spring. 



Known in Europe in France, Germany, and Italy as well as in the 

 United States. 



U.S.A. Exp. Sta. Cornell, xiv. Dec. 1889 ; Sacc. Syll. i. 1951 ; Mass, 

 PI. Dis. 107, fig. 18 ; Tubeuf, Dis. 215, fig. 



STRAWBERRY MILDEW. 

 Sphcerotheca Humuli (DC.). 



A white mould on Strawberries was recognised by Berkeley in 1854 y 

 when he imagined it was the same species as had been known on Turnips. 

 Afterwards the occurrence of the same mildew in America led to its 

 further investigation, and it was discovered at length to be none other 

 than a form of the well-known mildew of the Hop. In this country only 

 the conidial condition had been seen, which was a simple Oidium, some- 

 what like that of the Vine. On the other hand the perfect fruit was 

 found in America, so that between 1892 and 1898 it became established 

 that the fungus of the Strawberry mildew was that known as Sphcerotheca 

 Humuli (or, as formerly termed, Sphcerotheca Castagnei), the cause of the 

 Hop mildew. (Fig. 21.) 



In the first stage it attacks the leaves, causing them to curl, so as to 

 appear as if suffering for lack of water. At this time the mycelium 



