8 
BULLETIN 829, U. S. DEPARTMENT OF AGRICULTURE. 
each successive year. The figures in Table II were obtained by 
cutting all of the cane in approximately square patches, of about 
one-tenth to one-fifth of an acre selected in commercial fields and 
in the fields at the Sugar Experiment Station, Audubon Park, La. 
The stalks cut from such patches were then sorted into two classes, 
diseased and healthy, and the average weight of stalks in each class 
was determined. The patches were not selected at random, but an 
attempt was made to find areas where the mosaic was doing a maxi- 
mum amount of damage and at the same time a sufficient number of 
healthy plants were present in the patches, growing under identical 
conditions, in order to make a fair comparison possible. Since, if 
no attempt is made to control the disease in these fields, we may 
expect ultimately to find an infection of 100 per cent, the losses will 
then be equivalent to the figures found in column 5 of Table II. 
Table II. — Teste of sugar cane in Louisiana, showing the extent of losses in different 
varieties. 
Variety. 
Number of stalks- 
Healthy. Diseased 
Average weight of 
stalks — 
Healthy. Diseased 
Reduc- 
tion in 
.Diseased 
weight of 
stalks in 
diseased 
field. 
stalks. 
Per cent. 
Per cent. 
38 
32 
19 
27 
18 
34 
29 
28 
10 
45 
Loss in 
tonnage. 
Louisiana Purple. 
Louisiana Striped 
D-74 
D-95 
L-oll 
330 
268 
204 
348 
373 
160 
100 
108 
136 
310 
Pounds. 
1.13 
1.507 
1.27 
1.65 
.874 
Pounds. 
0.7 
1.22 
1.03 
1.16 
.787 
Per cent. 
12.16 
5.13 
6.12 
8.12 
4.5 
PRIMARY SYMPTOMS. 
Upon walking between the rows of cane in an affected field, more 
or less plants will be seen that are conspicuous on account of a gen- 
eral pallor of the leaves. This may be discernible for many rods. 
Closer examination of such plants reveals that the pallor is due to 
irregular light-colored streaks or spots on the leaves. The affected 
leaf areas, in so far as color is concerned, are of two distinct types. 
The most common type presents merely a "washed-out" appearance. 
It is, in fact, merely a tint of the normal color, in which the blue and 
yellow are present in the same proportions but diluted. In the sec- 
ond type, the yellow is predominant, and the affected areas have a 
decided yellowish green- appearance. The normal and affected areas 
are sharply demarked. In other words, there is no gradual merging 
of one color into the other. There is a great diversity of patterns 
in the different varieties, due to the variation in the amount, size, and 
shape of the light-colored areas, but the arrangement is so constant 
in any particular kind of cane that the character could be used as an 
aid in determining varieties. 
