262 



Diseases of Economic Plants 



Leaf -mold (Cladosporium fulvum Cke.), — Under glass 

 in the North and occasionally in the open, especially in the 

 South, this disease is destructive. It occurs as rusty or 

 cinnamon brown blotches on the lower side of the leaf, which 



turns yellow above, then 

 brown or black, curls, and 

 dies. The loss of food 

 supply consumed by the 

 parasite, together with the 

 loss through destruction 

 of the leaf green, injures 

 the yield seriously. 



Indoors ventilation is 

 the best remedy, coupled 

 with clean culture to avoid 

 carrying the pest over to 

 another year. On fields 

 Bordeaux mixture would 

 doubtless serve well. 



The causal fungus of 

 this disease was first de- 

 scribed in 1883 by Cooke 

 from specimens collected 

 in North Carolina. 



Leaf-spot ^^^ (Septoria 

 ly coper si ci Speg.). — A 

 very common leaf -spot 

 has almost precisely the 

 general appearance illus- 

 trated in Fig. 143, except 

 that small pycnidia occupy the spots. It is known through- 

 out the United States, South America, Europe, and Australia, 

 and often causes large loss. In some states it is the most 

 important tomato disease. The total loss in the United 

 States is estimated as $5,000,000 annually. 



The disease attacks the older loaves first and proceeds 

 toward the top of the plant, often causing the loss of so 



Fig. 143. — Tomato leaf 

 spots of mold. 



showing 



