250 Diseases of Greenhouse Crops 



at any part of the leaf and spread in all directions. 

 Cyclamen leaves are especially receptive to infec- 

 tion because of the fact that water is able to lodge 

 and remain a long time. 



Leaf Spot 



Caused by Phoma cyclamena Hals. 



Symptoms. The disease attacks leaves of all ages. 

 The affected portions become darkened. Later the 

 spots become dry and lighter in color, made up of 

 a series of concentric rings of light and dark bands. 

 The dead spots become brittle and drop out at the 

 least touch, giving the appearance of a shot hole. 

 This trouble is different from the leaf spot caused 

 by the Septoria cyclaminis Dur. and M. The causal 

 organisms of both of these leaf spots are little 

 known. 



Control, Removing the affected leaves and spray- 

 ing with a standard fungicide will materially assist 

 in keeping the disease in check. 



Dracenas (JDracena fragans) 



Cultural Considerations. The cultural require- 

 ments of Dracena are the same as for Cordyline, 

 see p. 247. 



Diseases of Dracenas 



Dracenas are usually considered a hardy plant. 

 However, they are subject to a few but serious 

 diseases. 



