RICE 105 



conditions vary greatly. Where it is the custom to 

 rest land, and especially under water, the situation may 

 be helped somewhat by omitting this practice and 

 cropping continuously. 



However, it is evident that for the future the 

 greatest dependence must be placed upon the discovery 

 of immune or highly resistant varieties. The fact that 

 this has already been accomplished in a large measure 

 for Italy, augurs well for other countries and con- 

 ditions. 



Other Diseases. Compared with blast, all other 

 diseases of rice are inconsequential. But a few may be 

 mentioned : Smut, caused by the fungus Tilletia 

 horrida, Tak., is probably the most serious of the minor 

 diseases. It is a native of Japan, and has been intro- 

 duced into America. Presumably it is amenable to the 

 same seed-treatment that is used in preventing smut of 

 other grains. 



Lump smut, caused by Ustilaginoidea virens, (Cke.) 

 Tak., is also a native of Japan, and has been introduced 

 into America. Individual grains become swollen and 

 malformed, presenting an appearance analogous to ergot. 

 In Japan this disease is regarded as a symbol of a 

 luxuriant crop, rather than a cause of loss ; and 

 apparently not enough grain is ever affected to do 

 serious harm. The disease is very conspicuous. 



The fungus Sclerotium oryzae, Catt., apparently 

 causes a stem rot under water, although the parasitism 

 of the fungus has not been demonstrated by inoculations. 

 This disease occurs locally in Italy and America. 



A disease of rice spoken of as straight-head, or 

 sterile-head, is apparently increasingly common in the 

 Gulf States. The grains simply fail to fill; in con- 

 sequence the heads stand erect. The plant appears 

 normal otherwise. The cause is unknown. 



Various apparently malnutrition diseases are re- 

 ported. Many of these have doubtless been confused 

 with blast. The best known of these, called " rust " in 

 South Carolina, from the rusty appearance of the leaves, 



