May 1, 1920 Artificial and Insect Transmission of Mosaic 



137 



Table II. — Effect of artificial inoculation of Lahaina cane with juice from cane unoxi' 



dized {virus No. 2) 



[Plants inoculated Jan. 7, 1920] 



DISCUSSION 



From the foregoing results it may be inferred that the sugar-cane 

 mosaic virus is highly infectious only when exacting demands in the 

 matter of favorable conditions are satisfied. Erratic spreading under 

 natural conditions in the field also indicates the necessity for special con- 

 ditions, which are not as yet known. It is considered as proved, however, 

 that the cell sap of diseased plants is infectious when introduced in the 

 proper manner and that the disease can be transmitted by insects. 

 Just what insects are responsible for dissemination in the cane regions 

 remains to be proved. The failure of the sharp-headed grain leaf hopper 

 to transmit the disease under the conditions of these experiments is 

 surprising. This insect is very common on cane in Louisiana, and as a 

 result of field observations suspicion was directed toward it from the 

 first. Other leaf hoppers are now being tested. The successful experi- 

 ments with the corn aphis is of great interest scientifically, but it is not 

 believed that transmission of mosaic is restricted to this insect or to other 

 aphids more abundant on cane. Aphis maidis, however, has been re- 

 ported on sugar cane from practically every sugar-cane region in the 

 world. 



That cane mosaic is analogous with other mosaic diseases is brought 

 out by a number of facts, aside from the visible signs of the disease. 

 As in many other mosaics, the infectious material does not seem to be 

 highly specialized, but may attack other plants of the same family. The 

 cell sap of infected plants contains some organism, not visible by ordinary 

 means, which is capable of inducing the disease when injected into healthy 

 plants. Leaves which are mature at the time of inoculation never show 

 any signs of mosaic. This fact, typical of all mosaics, has been brought 



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