3i6 Diseases of Greenhouse Crops 



and faded blossoms. These, therefore, act as a 

 source of infection. It is needless to add that clean- 

 liness will form a part of the control method. 

 Spraying with any of the standard fungicides is also 

 recommended. 



Anthracnose 



Caused by Colletotrichum primultz Hals. 



Symptoms. AfiFected leaves become brown and 

 spotted. The spots are more visible on the lower 

 part of the foliage (fig. 63, c). The acervuli 

 with its black setse of the causal organism are 

 especially conspicuous when looked at with a mag- 

 nifying lens. At present little is known of the 

 organism. The disease may be kept in check by 

 spraying with a standard fungicide. 



Blioht 



Caused by Phyllosticta primulicola Desm. 



Symptoms. On the leaves of the plant appear 

 somewhat circular spots (fig. 63, b) that are brown 

 or whitish in color with a light border, with which 

 are found numerous pycnidia. The disease attacks 

 various species of the genus Primula with different 

 effects. On P. sieboldii and on P. obconia, the trouble 

 is usually confined to the lower leaves. On P. 

 sinensis the central part of the leaf is attacked be- 

 fore the surrounding tissue loses its color. On P. 

 sieboldii the leaves may often be blotched through- 

 out, while on P. obconia one-half of the leaf is 



