204 Diseases of Truck Crops 



that leaf warts may be produced by spraying with 

 weak solutions of copper chloride, copper acetate, 

 copper nitrate, and copper sulphate. 



Ring Spot 



Caused by Mycosphcerella brassicola (Duby) Lind. 



The exact distribution of this disease is as yet un- 

 known. The trouble was studied by Osmun and 

 Anderson 1 on cauliflowers shipped from California 

 to Boston. 



Symptoms. On the leaves, the disease appears as 

 numerous small spots and the affected foliage turns 

 yellow. Most of the spots are formed on the lamina?, 

 but others are also formed on the large midribs. 

 The spots are definite in outline, round and visible 

 on both surfaces of the leaf (fig. 33 f). The color is 

 light brown to gray, with dry centers surrounded by 

 olive green or blue green borders which shade off in 

 the natural color of the leaf. The outer edge of the 

 spot is covered with the fruit of the fungus (fig. 33 

 g-i). Ring spot also attacks the cabbage. Spray- 

 ing with 4-4-50 Bordeaux is recommended. 



DISEASES OF THE HORSERADISH (Cochlearia 



armoracia) 



The horseradish is generally considered a hardy 

 plant. However, it is subject to numerous diseases. 



1 Osmun, A. V., and Anderson, P. G., Phytopath. 5: 260-265,1915. 



