262 Diseases of Greenhouse Crops 



evenly distributed. The specks, however, differ in 

 form. Some are very irregular in outline while 

 others are almost circular. 



Cause. Dropsy is favored by poor light, wet soil, 

 and a high soil temperature. Dropsy may be looked 

 for in late winter with long nights, short days and 

 cloudy weather. This causes an excessive root ac- 

 tion with results injurious to the plant. 



Control, Dropsy may be controlled by providing 

 a cooler, dryer soil, and by exposing the plants to 

 the direction where they will receive the greatest 

 amount of light and ventilation. 



Leaf Spot 



Caused by Fseudomonas erodii Lewis. 



Symptoms, This disease was found by Lewis * 

 on greenhouse geraniums in Texas. It is not known 

 how serious or how extensive the disease may ap- 

 pear to be in different parts of the country. It is to 

 be assumed that it is more or less prevalent in every 

 greenhouse where it has been spread about by infect- 

 ed plants or cuttings. 



The disease attacks four varieties of ornamental 

 geraniums and the symptoms are the same on all. 

 On the leaves, the spots first appear as minute dots 

 which are transparent through light. With age the 

 spots enlarge, become reddish brown in the center 

 with ^a colorless border, resembling much the frog 

 eye spot of the apple (fig. 56, d and e.). There 



* Lewis, I. M., Phytopath, 4:221-231, 1914. 



