502 
Journal o f Agricultural Research 
Vol. XXIX, No. 10 
RAPIDITY OF NATURAL INFECTION 
OF CANE MOSAIC 
The first work attempted with the 
sugar cane mosaic was to test out the 
different varieties of cane that are grown 
in Louisiana. It was very soon deter¬ 
mined that the common commercial 
varieties, including D 74, D 95, Purple 
and Striped, were very susceptible to 
the mosaic, and that if healthy cane is 
planted in a badly infected field the 
crop will show practically 100 per cent 
infection before the end of the first 
season. It was also determined that 
diseased canes of these varieties when 
planted produced diseased plants the 
next year. This is in accord with the 
prevailing opinion in regard to mosaic 
transmission. In Table I are given the 
results of a few tests showing the rapid 
increase of mosaic on some of the sus¬ 
ceptible canes when grown in a badly 
infected field. 
percentage of the plants in a field 
show the presence of the disease. One of 
the reasons for this has been determined 
to be the resistance of the plants to in¬ 
fection. Resistance to infection should 
be kept distinct from the relative sever¬ 
ity of the disease after infection occurs. 
The L 511 is one of the canes which 
shows the mosaic on the stalks as 
well as on the leaves. Healthy stalks 
are a light green in color but diseased 
ones have red stripes running in the 
direction of the main axis. For a 
number of years stalks lacking these 
stripes, that is, stalks free of the 
mosaic, have been selected and planted 
and the crop watched through the 
following year. The increase in mosaic 
on these plats is shown in Table II. 
In all cases the increase in mosaic has 
been very slow as compared to that on 
susceptible cane varieties. This shows 
a resistance to the infection but has 
no reference to the severity of the dis- 
Table I.— Rate of increase of mosaic infection on susceptible canes 
Percentage of mosaic on different dates 
Year 
Variety 
May 
June 
July 
August 
Septem¬ 
ber 
1920 “. _ 
D 74_ 
100.0 
1920 °_ 
D 95_ . 
100.0 
1921_ 
Palfrey_ .... 
4.4 
56.6 
100.0 
1922.. _ 
.do_ . 
1.9 
36.6 
47.0 
( b ) 
1922.. . 
Purple.. 
0.0 
42.1 
63.0 
(*) 
1922. . . 
D 74_ . 
1.8 
17.8 
64.0 
— 
° Most of the data for 1920 was lost by fire. 
b The cane was examined in September, 1922, but since all of the plats showed practically 100 per cent 
infection counts were not made. 
RESISTANCE TO INFECTION 
It was noted, however, that cane of 
another variety known as L 511, acted 
in a manner different from the common 
canes. The L 511 is one of the canes 
developed at the Louisiana Experi¬ 
ment Station. it is very rich in su¬ 
crose, but, since the tonnage is usually 
light, it is not becoming generally 
planted. Plants of this variety when 
affected with mosaic show the disease 
in a form as severe as that of any of 
the other varieties, but only a moderate 
ease following infection. The stalks 
that became affected showed the dis¬ 
ease in as intense a form as do sus¬ 
ceptible varieties. To what this resis¬ 
tance to infection is due has not been 
definitely determined. It may, how¬ 
ever, be the result of a better protection 
of the growing bud. The cluster of 
leaves at the top of a stalk of L 511 
cane is much more compact than that 
on most varieties, and it is possible 
that this hinders the insects which carry 
the mosaic from attacking the young 
bud. 
Table II.— Rate of increase of mosaic infection on L 511 cane 
Year 
Percentage of mosaic on different dates 
! October n 
! 
May 
2.2 
13.6 
1 
June 
July ! August Se P£ m - 
! . — 
1921. _ . 
21.5 55.0 
43.7 
22.6 
1 9.2 
1922_ 
8.9 
9.2 
19.0 24.0 
1923_ 
10. 3 I _ 12.3 
a The October counts were made at the time when the cane was being cut for planting and were based 
on the number of stalks that showed the presence of red stripes. The other counts were based on the 
quantity of leaf infection apparent on the growing cane. 
