OBNAMENTAL PLANTS 



463 



Ascochytose, ray blight (Ascochyta chrysanthemi Stevens). 



— In this disease, described by Stevens' as doing consider- 

 able damage in North Caro- 

 lina, the ray flowers are 

 blighted, resulting in im- 

 perfect opening of the buds. 

 Thorough spraying with 

 Bordeaux mixture from the 

 beginning of the season un- 

 til blossoming, accompanied 

 by destruction of infected 

 refuse, has proved a satis- 

 factory treatment. 



Powdery mildew (Oidium 

 chrysanthemi Rbh. of Ery- 

 siphe cichoracearum DC). 



— This mildew occurs as 

 white, flour -like spots upon 

 the green parts of the plant. 

 It is not often serious, but 

 if it should be, can probably 

 readily be controlled by the 

 means suggested for grape 

 oidiose. 



Cylindrosporiose (Cylin- 

 drosporium chrysanthemi 



Ell. & Dearn). — First described in 1893, this closely re- 

 sembles septoriose, though it develops somewhat more 

 rapidly and is consequently more injurious. Often the 

 leaves die and flowers fail to form. Treatment is the same 

 as for septoriose. 



1 Stevena, F. L., Bot. Gaz. U, 241, October, 1907. 



Fig. 200. — Chrysanthemum blossom dis- 

 torted with ray blight. Original. 



