194 



DISEASES OF CULTIVATED PLANTS 



Strawberry leaf spot. Both cultivated and wild straw- 

 berries are often severely damaged by a fungus named 

 Sphaerella fragariae (Tul.), the conidial form of which was at 

 one time the only stage known, and was called Ramularia 

 Tulasfiei (Rab.). Small reddish-brown patches first appear 

 on the leaves, which continue to increase in size for 

 some time and frequently encroach on each other, forming 



Fig. 52. Sphaerella fragaritxe, 1, .1 diseased straw- 

 berry leaf; 2, ascus containing eight spores of the 

 Sphaerella or ascigerous stage ; 3, conidia of the 

 Ramularia or conidial stage. Figs. 2 and 3 highly 

 mag. 



irregular patches. By degrees the centre of the patch assumes 

 an ashy-grey or almost white colour, and is bounded by a 

 reddish border, which is often quite bright in colour later in 

 the season. The central portion then becomes studded with 

 very minute white tufts of the conidial form of fruit. Later 

 in the season these minute white tufts are replaced by 

 minute black points the ascigerous phase of the fungus. 

 Minute sclerotia are also frequently formed in abundance 

 on diseased fading leaves. This pest is everywhere present 



