196 Diseases of Truck Crops 



Treatment. Manns recommends treatment of the 

 seed bed with 4-4-50 Bordeaux to be applied im- 

 mediately after planting, at the rate of one gallon to 

 each ten square feet of bed space. The bed is again 

 sprayed with Bordeaux about two weeks before and 

 once again at transplanting. 



BLACK MOLD 

 Caused by Alternaria brassica (Berk.) Sacc. 



Black mold is a serious disease of the cabbage in 

 the Southern States. It also attacks collards. 



Symptoms. Affected leaves are covered with 

 spots which are nearly black on the under side of the 

 leaf. The spots are composed of a series of rings, 

 the smaller ones enclosed within the larger (fig. 31 a). 

 There is no distinct border separating the diseased 

 from the healthy, the spots gradually shading off 

 into the healthy tissue. Little is known of the causa- 

 tive fungus or of the control of this disease. It is 

 probable that spraying with 4-4-50 Bordeaux will 

 be of value. 



LEAF SPOT 

 Caused by Cercospora bloxami B. and Br. 



Leaf spot is of little economic importance. It only 

 attacks the leaves of weak or languid plants. The 

 spots are pale, somewhat circular, surrounded by a 

 slightly raised, faintly purple border. The conidial 



