Aug. i6. 1920 Mosaic Disease of Corn 521 



way that may throw some light on this phase of the problem. It has 

 been proved that the virus of corn mosaic is identical with that of sugar- 

 cane and sorghum mosaic, so that even if it is found not to be seed- 

 borne, perpetuation of the disease in the perenniai grasses would explain 

 its appearance on com in the spring. 



Artificial transmission of the disease by means of inoculation with 

 expressed cell sap of afifected plants has not been attempted for com. 

 This method has proved successful in sugar cane, however,^ and there is 

 little doubt that the infectious material is contained in the cell sap of 

 com. Just what this infectious material is can not be stated definitely, 

 but the evidence points strongly toward a living organism. No evi- 

 dence incompatible with this view has been put forward for any mosaic 

 disease, excepting the failure to demonstrate any visible organism. 



CONTROL 



Control measures for this disease must be based fundamentally on 

 the removal of sources of the inoculum. So far as is known the only 

 sources of inoculum are the living host plants. Destruction of these 

 plants, then, will effectively eradicate the disease from any region. 

 Practically, the destruction of all affected host plants presents almost 

 unsurmountable obstacles. An immense amount of sugar cane is now 

 infected in the River District of Louisiana and in southern Georgia. 

 Destruction of large numbers of plants by roguing or plowing up is viewed 

 with great concern by the planters, most of whom oppose any plan to 

 control the disease by eradication. The substitution of immune varieties 

 of com as well as cane does not offer any immediate solution, since the 

 most susceptible varieties happen to be the ones most esteemed. Elimi- 

 nation of this disease is dependent upon the education of the planter 

 to an understanding of its seriousness. When this is accomplished 

 public sentiment will permit of the passage of compulsory roguing and 

 quarantine laws, which will be necessary before any hope can be enter- 

 tained of eliminating the disease. 



1 Brandes, E.W. ARTIFICIAL AND INSBCT TRANSMISSION OF SUGAH-CANB MOSAIC, /n JouT. Agr. Research, 

 V. 19, no. 3, p. 131-138. 1920. Literature cited, p. 138. 



