CHAPTER 18 



ASTER (Aster sp.) 



Cultural Considerations^ see Chrysanthemum, p. 

 235. 



Diseases of the Aster 



Although considered a hardy plant, asters are sub- 

 ject to some important diseases when grown under 

 greenhouse conditions. 



Yellows 

 Cause, physiological. 



Symptoms. This is a very obscure disease, the 

 cause of which is little understood. It has been in- 

 vestigated by Smith, who, however, reached no 

 definite conclusions. The roots of affected plants 

 are apparently normal in every respect. The stems 

 and branches, however, become pale yellow, slender 

 and spindly, and in extreme cases stunted. The 

 leaves too are often stunted and poorly developed. 

 The flower bracts show no change, the calyx (se- 

 pals) has a tendency to revert to leaf-like lobes. 

 The color of the corolla changes to a uniform light 

 greenish yellow irrespective of the original color of 



* Smith, R. E., Mass. (Hatch) Agr. Expt. Sta., Bui. 79: 3-26, 1902. 



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