Family Cruciferae 217 



Macrosporium Leaf Spot 



Caused by Macrosporium herculeum E. and M. 



Leaf spot often attacks the flat turnip and horse- 

 radish. On turnips it is manifested as brittle circular 

 spots on the leaf (fig. 37 a). When numerous, the 

 spots usually fall out, giving a shot-hole appearance. 

 The long club-shaped spores (fig. 37 c) of the fimgus 

 are borne on long conidiophores (fig. 37 b) on the 

 exterior of the dead tissue. Should treatment seem 

 advisable, spraying with Bordeaux mixture is re- 

 commended. 



Weeds 



Of the many cruciferous weeds which truckers have 

 to contend with, the following few may be mentioned : 

 Winter cress {Barbarea vulgaris), shepherd's purse 

 {Capsella bursa-pastoris) , cow cress (Lepidium cam- 

 pestre), pepper grass {Lepidium virginicum) . The 

 above mentioned weeds and many other crucifers 

 are subject to club root, black rot, white rust, and 

 downy mildew. 



It is evident therefore that clean culture is impor- 

 tant. These weeds must not be tolerated if we are 

 completely to eradicate the diseases of the cultivated 

 crudfers. 



