CULTIVATED AND WILD HOSTS OF SUGAR-CANE OR 
GRASS MOSAICS 
By E. W. BiiandBS, Pathologist, and Pbter J. Kxaphaak, Assistant Paihologist, 
Office of Sugaf‘Plant Jfii>estigations, Bureau of Plant Industry, United States Depart^ 
fnent of Agrkultufe 
PURPOSE OF THE INVESTIGATION 
Since 1919, when it was demonstrated by the senior writer that grasses 
other ^an sugar cane are susceptible to the so-called sugar-cane mosaie 
i3y 4* 5 )? a large number of experiments have been performed to deter¬ 
mine whether grasses in general are susceptible. It tos especially 
important to learn whether the forage and field crops of the South are 
affected and, if so, to what extent damage is caused. On accoimt of 
the comparatively recent introduction of the disease on sugar cane into 
this country, it was expected that crops in the vicinity of diseased sugar 
cane would be more likely to be affected. Accordingly these crops were 
closely scrutinized for symptoms similar to those on sugar cane, and 
when suspected cases were observed the plants were tested experimentally 
at Washington. Other closely related cultivated plants w^i^ tested, 
whether or not they showed signs of natural infection in the fields. 
Another class of grasses, namely, the weeds or wild grasses found in 
sugar-cane fields, was held under observation, and any species^ which 
showed signs of disease were similarly tested. The importance of 
having exact knowledge of the susceptibility of wild.grasses to grass 
mosaic lies in the fact that the disease may be carried over winter in 
perennial grasses and may reinfect the susceptible annual grass crops 
in the spring. 
The r61e of wild perennial hosts in preserving the virus of mosaic 
through the winter has not been fully established, but they mii$t be 
regarded as a potential source of danger, and our studies are justified 
on these grounds. In the South, even the annual grasses may be found 
in the growing state during the whole year. Sugar cane itself is a peren¬ 
nial, and the virus of mosaic is known to survive the winter in tte stubble, 
as the ratoon plants invariably come up divseased in the spring n the 
plants of the previous year were infected. The attempt has been made 
in some regions to eradicate the disease by destroying all. infected cane 
stools or by plowing out whole fields and planting to other crops for a 
year or more. The labor of course would be wasted if the disease were 
perpetuated in some unobserved wild perennial host. This method of 
eradication has been successful, however, in at least one sugar-cane 
region. Where thC disease Was early Observed and prompt and vigorOtis 
measures were taken to stamp it out. This region is the peninsular 
section of Florida where the disease no longer exists to our knowledge. 
More than 40 grasses have been tested experimentally, either by arti¬ 
ficial inoculation or by means of insect inoculation or both. 
' Accepted for publication Dec. i, 1921. 
* Reference is made by number (italic) to ** Literature cited, *’ p. 262. 
Vol. XXIV, No. 3 
Apr. 21, 1923 
Key No. (^297 
Journal of Agricultural Research, 
Washington, D. C. 
adj 
(247) 
