202 Diseases of Greenhouse Crops 



quently met with. The exact life history of this 

 fungus is as yet imperfectly known. 



Control. In the greenhouse, the disease is only 

 prevalent on snapdragon propagated by cuttings 

 taken from outdoor plants. In this case, the dis- 

 ease is brought in directly with infected cuttings. 

 The only remedy known is to use healthy cuttings. 

 The safest is to use plants started from seeds sown 

 indoors. 



Anthracnose 



Caused by Colletotrichum antirrhini Stew. 



Symptoms. Anthracnose is a common disease on 

 greenhouse and garden snapdragons. In the green- 

 house, it is more troublesome in the fall and spring. 

 The disease attacks the stems (fig. 40, d) in all 

 stages of development. It appears as a large spot 

 on the stems or lateral shoots, resulting in their 

 death (fig. 41, a and b). The spots are at first dirty 

 white with a narrow border. Soon, however, the 

 center turns black and under conditions of moisture, 

 becomes covered with the acervuli of the causal or- 

 ganism. On the leaves (fig. 40, d) the spots are 

 circular, slightly sunken, at first yellowish green 

 with indefinite outline, and later becoming dirty 

 white or greenish, definitely outlined and limited 

 by a narrow brown border. The spots, when nu- 

 merous, spread and blend together. The affected 

 foliage shrivels, clings to the stems and dies. 



