474 



DISEASES OF ECONOMIC PLANTS 



nearly so. The larger spots are a centimeter or more in 

 diameter, and they frequently coalesce so as to nearly 

 cover whole leaflets. 



With age the spots turn gray at the centers, at which part 

 the leaf dies. They also become more regular in outline 



Fig. 201. — -Rose mildew ; diseased and liealthy shoots. Original. 



than in their earlier stages. Portions of the leaflets out- 

 side of the area actually spotted often turn yellow, and the 

 diseased leaflets fall off prematurely. Thus the beds be- 

 neath diseased plants are often strewn with fallen leaves. 

 All infective material should be gathered and burned, and 

 both bushes and ground be well cleared of superficial spores 



