96 DISEASES OF TROPICAL PLANTS CH . 



burned as soon as the disease is detected. When the 

 disease is not sufficiently troublesome to necessitate this 

 treatment it is always advisable to rake and burn the 

 old stalks before planting a new crop. 



A smut ( Ustilago sorghi, (Link) Pass), also attacks 

 the Kaffir corn in Cuba, and probably occurs on other 

 cereals. It completely destroys the grain, leaving only 

 a black dust. (See treatment for smut, page 280). 



Mildew. A mildew which is due to Peronospora 



FIG. 44. Ear of corn destroyed by smut. (After Cook and Home, Bui. 7, Estacion 

 Central Agronomics de Cuba. ) 



maydis, Eacib., has been reported from Java. It 

 attacks the young plants, causing them to lose colour, 

 droop, and die. It is supposed to exist on some of the 

 native grasses from which it passes to the young corn. 



Rust. Corn is also subject to two well-known 

 rusts (Puccinia sorghi, Schw. smdP.purpurea, Cooke), 

 but they do comparatively little damage, and there is 

 no effective method of preventing them. When 

 abundant they cause the leaves to dry prematurely 

 and thus reduce their value for feed. 



P. purpurea, Cooke, also attacks many other related 



