PRESS BULLETIN 150
florida Agricullural Experiment Station
RED ROT OF SUGAR-CANE
By H. S. Fawcett
The disease known as Red Rot, due to the fungus Colletotrichumfalcatum,
has made its appearance in two counties in northern Florida. Much of the
bedded cane throughout that section has been rendered unfit for planting.
Only recently has this disease been known to occur in the United States,
though it has been reported from Hawaii, West Indies, Bengal, Madras,
Java, and Queensland.
The disease has characteristic marks inside the canes by which it may
be recognized, but is difficult to recognize externally. It is therefore apt
to be overlooked until it becomes so serious as to attract attention. When
the diseased canes are split lengthwise the soft tissue of the internodes
shows a reddish discoloration. In these red discolored areas are found
white spots which shade off into the red. These white spots are especially
characteristic of Red Rot. As the disease advances the central portion of
the stem gives way, forming a long straight cavity, in which is a whitish
mold made up of fungus threads. The nodes and buds become first brown,
and finally black. The hard outside of the. stalk remains apparently un-
changed. When the disease has not progressed so far as this, the canes
may appear at first glance to be healthy; but when they are split length-
wise the soft tissue in the internodes will show the beginnings of the
disease as small reddish patches. Because it is so easily overlooked, the
grower should keep a watch for it. There are other diseases that may cause
reddening of the soft tissue, but if there are also white patches within the
red areas, the disease may be pronounced Red Rot.
Although Red Rot is usually not noticed until the cane is cut for
planting, it may be present during the summer. In some cases the fungus
causing Red Rot may seriously check the growth of the plant during the
summer, and redden the leaves and the soft tissue inside the canes.
The fungus attacks the plant most easily through wounds or holes made by
borers. It appears to get to the growing plant, however, mostly by means
of the planted cuttings, and does not spread much through the air. Usually
May 14, 1910
the injury is only slight during the growing season. At the bedding
season, however, the fungus is present ready to cause serious damage to
the dormant canes. It is at this time that the fungus grows, advances into
the interior of the canes, and kills the buds. In the beds decay appears to
start mostly at the ends of the canes, although it may also start at other
places along the canes.
The cause of Red Rot is a fungus. A microscopical examination of the
interior of the diseased Florida canes showed that the fungus was present
in the cells in all stages of the reddening. Pure cultures of the fungus
were obtained from the reddened areas and on examination it proved to be
Coletotrichum falcatum. This fungus was first described in connection
with the disease when it was discovered in Java by Went, in 1893.
Means of Control
1. Plant only healthy canes. In Hawaii and other places, it has been
found that this disease may be easily and successfully controlled by planting
only healthy canes that show no sign of discoloration. Any canes showing
even the slightest discoloration of the interior should be discarded. It will
be necessary, in sections where the disease has become prevalent, to grind
all the cane, and get seed cane for planting from some other locality.
2. As an extra preventive the selected canes may be dipped in Bor-
deaux mixture just before they are planted. This will kill any fungus that
may have gotten onto the cut ends or surfaces. A large wooden trough
is convenient for holding the Bordeaux mixture while dipping. The formula,
5 pounds of copper sulphate, 5 pounds of lime, and 50 gallons of water, may
be used. The cost is but slight.
3. Whenever possible plant the canes in the fall instead of bedding
them. Planting the cane in the fall will give one an opportunity to discover
the disease, if present, and will do away with danger from contamination
in the bed.
4. A method of dealing with the disease that has been practiced in
the West Indies is to plant some other variety of cane that is not so sub-
ject to the Red Rot.
5. Burn all the trash in the old bed, and all diseased cane.
State papers please copy.