22 BULLETIN 829, U. S. DEPAETMEXT OF AGEICrLTUEE. 
Since there are as vet no certain means of determining the latter 
fact, a second inspection is essential. It should be made from 25 
to 30 days after the first, a lapse of time sufficiently in excess of the 
incubation period for mosaic to insure recognition of the disease in 
plants inoculated prior to the first inspection. If no diseased plants 
are found during the second inspection, it can be assumed that 
secondary infection is not in operation and that the remaining 
plants will continue healthy. If diseased plants are found, how- 
ever, it establishes the fact that secondary infections are going on. 
The field should be rogued as before, and a third inspection made 
after the same interval, i. e., 25 to 30 days. If the carriers remain 
active it may be necessary to repeat the process several times, and 
owing to the impossibility of recognizing the disease in inoculated 
plants before the end of the incubation period it is certain that 
plants which have become infected just before the inspection is 
made will escape detection. This emphasizes the necessity for 
making the first inspection early, preferably before leafhoppers or 
other sucking insects have appeared on the plants. 
This procedure may result in perfect control or eradication of the 
disease or in partial control, the element of uncertainty being due to 
our inability to control the carriers. By it their activity can be 
rendered less effective by reducing the sources of inoculum to a 
mhiimum. It has effectually halted the progress of the disease into 
new territory in Porto Rico. 
ELIMINATION BY GRINDING ALL CANE AND SECURING CLEAN SEED. 
In badly infested sections the problem is manifestly complicated. 
"VThere 25 to 60 per cent or more of the plants in large fields are 
diseased, roguing is obviously out of the question. Such plantings 
should be allowed to mature. Every stalk of it should be ground, 
however, and the stubble plowed up and killed. This means, of 
course, that carefully selected seed must be imported for replanting. 
Fortunately there is still an abundance of healthy stock in Louisiana 
and other cane sections in the United States. As a result of its 
recent exhaustive smwey for mosiac disease, the Office of Sugar- 
Plant Investigations of the Bureau of Plant Industry is in a position 
to furnish information on the nearest or most accessible source of 
clean seed for any region. Data have been secured on the prevalence 
of other diseases and insect pests in all cane regions, so that reason- 
able security against the dissemination of other cane maladies is 
assured. 
EXCLUSION. 
There are at the present time (October, 1919) a number of large 
cane areas in the United States not yet invaded by the mosaic 
disease. Cane planters in these areas should urge the enactment of 
