28o 
Journal of Agricultural Research voi xxiii, No. 4 
Ledeboer (6), in Java, announced that he had obtained results which 
indicated that Aphis sacchari as well as A. maidis could transmit the 
disease. In a later publication (7) he states that while his experiments 
with A. maidis had confirmed the work of Brandes (/), his preliminary 
experiments with A . sacchari were not now considered conclusive. He 
made the observation in this paper that A. maidis was noticed to be 
very abundant on Panicum colonum and Paspalum sanguinale in the 
sugar-cane fields and that the winged forms occasionally flew from these 
grasses to the sugar cane. He states further that these grasses are 
subject to the cane mosaic. 
Bruner ( 2) published the results of careful experiments with a great 
variety of cane insects conducted at Santiago de las Vegas, Cuba. Aphis 
maidis alone was able to serve as a vector of mosaic. He states, how¬ 
ever, that this insect does not attack sugar cane under field conditions 
and therefore can not be held responsible for dissemination of the disease 
in nature. 
Wolcott (rr), who studied insects in relation to this disease in Porto 
Rico, states in reference to Aphis maidis: 
The Corn aphis has not been found on cane in Porto Rico. It can not in any way 
be considered responsible for the transmission of mosaic disease of sugar cane under 
field conditions in Porto Rico. 
In another publication (12) he says: 
. . . Mr. Smythe was unable to keep it [Aphis maidis ] alive on sugar cane in Porto 
Rico. The experimental transmission by an insect which will live on sugar cane 
only under abnormal conditions [referring to the experiments of Brandes] proves 
nothing as to the insect responsible for transmission in the field, except to indicate 
the plac e on the cane plant where the insect must feed to cause the disease. 
Kunkel (5), in Hawaii, performed careful experiments in which he 
confirmed the ability of Aphis maidis to transmit the disease, but was 
unable to demonstrate this ability on the part of A . sacchari . He also 
proves convincingly that the com leafhopper (Peregrinus maidis) is able 
to transmit the disease from com to com but, strangely enough, not to 
sugar cane. Kunkel makes the important observation that a rapid 
spread of mosaic in sugar cane followed the weeding of a field. In the 
case cited, the field was infested with goose grass (Eleusine indica) t 
some of which had the mosaic. A. maidis was abundant on the goose 
grass previous to weeding, and probably migrated to the cane at that 
time. 
Chardon and Veve (4) conducted experiments in Porto Rico in which 
mosaic and healthy sugar-cane plants in a field were covered with cheese 
cloth, and A. maidis was introduced into the cage thus formed. The 
insects colonized on various grasses, including Eleusine indica , Echino - 
chloa colona , and Panicum barbinode t which were growing as weeds in the 
cage. The weeds were then cut down and the aphids were observed to 
migrate to the cane. About 65 per cent of the healthy plants in this 
cage became mosaic during a period of 66 days, the first case appearing 
14 days after the migration. In a second similar cage, into which no 
specimens of A. maidis were introduced, no cases appeared among the 
healthy plants. A somewhat similar experiment with a different species 
of plant louse ( Carolinaia sp.) which occurs on the sedge, Cyperus 
rotundus, was reported in the same paper. Four out of six plants in the 
experiment became mosaic, but since no control plants appear to have 
been used it needs repetition under better controlled conditions. 
