418 Diseases of Economic Plants 



CHRYSANTHEMUM 



Leaf-spot ^•^•'' {Septoria chrysanthemella Cav.). — Large 

 brown to black blotches, often irregularly circular and of 

 indefinite border, appear upon the leaves. These enlarge and 

 coalesce to involve the whole leaf, which withers, dies, and 

 falls away. 



The lower leaves are first affected, but in later stages all 

 the leaves of the plant may be badly spotted, and practically 

 complete defoliation may result. Cuttings from infected 

 stock should be avoided. All diseased foliage should be 

 picked, collected, and burned, and the remaining foliage 

 should be sprayed with Bordeaux mixture with addition of 

 soap sufficient to form a suds to increase its adhesive power. 

 Five or six sprayings during the season are usually sufficient. 

 Leaf-spot (Phyllostida chrysanthemi E. & D.). — This 

 disease, first described in 1893, 

 is very similar to the above, ex- 

 cept that the spots are more 

 regularly circular, are purplish 

 brown, and have a distinct 

 border. Pycnidia which may 

 often be seen with the naked eye 

 are present. 



Wilt (Fusarium sp.) occurs 

 occasionally. 



Rust ^^^ {Puccinia chrysan- 

 themi Roze) . — Apparently a na- 

 tive of Japan, the rust was 

 introduced into England (1895) 

 and Europe through commercial 

 agencies, and similarly into the 

 Fig. 218. — Chrysanthemum United States, where it was first 

 leaf shoeing rust son. Ong- ^^^^^ .^ ^^^^ .^ Massachusetts. 



It was rapidly spread throughout 

 this country by diseased stock, and is now known in nearly 

 all localities where the chrysanthemum is cultivated. The 



