5i8 Journal of Agricultural Research voi. xix, no. w 



Diseases of corn bearing a decided resemblance to the one in question 

 have been reported from other countries. Dr. H. L. Lyon states ^ that 

 in the Hawaiian Islands a disease of corn which resembles sugar-cane 

 mosaic is very serious. William H. Weston ^ describes a disease of com 

 in Guam which may be identical with the one under discussion. He 

 mentions yellowing and dwarfing among the symptoms and states that 

 the leaves exhibited mottling and striping. 



VARIETAL SUSCEPTIBILITY 



Just enough work has been done on varietal susceptibility to prove 

 that all varieties of corn do not respond in the same way. The writer 

 has never seen such excessive injury as that described for the unknown 

 variety in Guam by Weston. In Louisiana the injury to com of the 

 White Creole variety, while marked in some individuals, was not ex- 

 cessive, excepting when the plants were infected early in the spring. 

 The variety U. S. Select No. 182 is very susceptible to mosaic, but is 

 not especially injured by it. Golden Bantam sweetcorn could not be 

 infected in the greenhouse by methods which were successful with 

 U. S. Select No. 182. Golden Bantam was planted unprotected in a 

 greenhouse with hundreds of infected sugar-cane and sorghum plants. 

 The corn aphis quickly migrated to the young com plants from diseased 

 sorghum in great numbers, but no cases appeared among the Golden 

 Bantam seedlings. It seems probable that this variety is immune. 



IMPORTANCE 



No figures are available on the amount of loss sustained on account of 

 injury to corn. The writer is inclined to believe that in this country no 

 great damage has been done thus far. Probably the disease was intro- 

 duced on sugar cane within comparatively recent years, in which case it - 

 may become more important in the future. At present, however, our 

 chief concern is with its relation to the sugar-cane crop. Com is almost 

 invariably used in the rotation on sugar-cane land, so that no planta- 

 tion is ever without com in some of its fields. This means, of course, 

 that the possibility for spread of the disease is greatly increased. Over- 

 wintering by the vims has been demonstrated only in the vegetative 

 portions of the sugar-cane plant, but the existence of other graminaceous 

 hosts certainly complicates the problem of control. 



SYMPTOMS 



In com as in sugar cane the most conspicuous symptom of mosaic is 

 the streaked and irregularly mottled appearance of the leaves. In corn, 

 however, the lower, older leaves have a greater tendency to resume 

 their normal color, so that it is sometimes difficult to demonstrate the 



1 In verbal communication, January, 1920. 



' Weston, W. H. report on the plant disease situation in guam. Guam Agr. Exp. Sta. Rpt. 

 X917, p. 45-62- 1918. 



