PRESS BULLETIN 131
Florida Agricullural Experimen t Slailon
STEM-END ROT OF CITRUS FRUITS
By H. S. FAWCETT
A new soft-rot has this year made its appearance in a serious form, on
grapefruit, oranges, and tangerines, in a number of counties in Florida. At
the present time it appears to be a disease which, if not checked, will destroy
large quantities of fruit.
This disease appears to attack full-sized fruits on the trees, after they
have colored, and to cause them to drop. In some groves many of the grape-
fruit have been reported as dropping from this cause. The disease may also
develop on the fruit after it is packed.
The fruit first begins to soften and sink a little at the stem end, without
the rind changing color. There is no blackening nor molding at first, and the
softened peel remains intact over the softened interior. The softening pro-
ceeds inward along the fibers of the rag, and then outward into the pulp cells.
At first the inside of the fruit remains almost unchanged in color; but, as the
softening goes on, the' diseased pulp turns dull brown. *
OTHER CITRUS FRUIT-ROTS
This rotting or softening is quite different from the well-known citrus
fruit-rots, due to the withertip fungus, or to common moldq. In the rotting
of mature fruit due to the withertip fungus, the rind becomes darkened in
brown sunken spots before the inside of the fruit is injured, if it is injured at
In the rotting of citrus fruits due to the Penicillium fungi, or molds, as
they are usually called, a softening takes place, but it is not confined to the
stem end. A moldy odor is perceptible; and, as the rotting progresses, a
green or blue mat of fungus spores is produced.
Microscopical examination of the diseased fruits showed that the softened
tissue was filled with colorless fungus threads, which branched many times.
This fungus is different from any yet found in connection with rotting citrus
fruits, and it appears to be the cause of the peculiar softening. Infection ex-
periments are in progress to prove this point.
November 27, 1909
A SUGGESTION AS TO TREATMENT
As the pathologist has not yet had an opportunity to make experiments in
the control of this disease, he can give only a suggestion as to treatment. If
the fungus enters while the fruit is on the tree, as seems probable, it is possi-
ble that spraying with ammoniacal solution of copper carbonate would be
fairly effective in checking the dropping of fruit from this cause.
In order to make a study of this disease, and to ascertain its severity and
distribution, the Plant Pathologist desires to get specimens from as many lo-
calities as possible, and to receive all the information he can in regard to it.
Any grower who is troubled with such a soft rotting of citrus fruits, is re-
quested to send two or three affected fruits to the Plant Pathologist, Agricul-
tural Experiment Station, Gainesville, Fla. Everyone who will do so will be
advised what to do for the trouble, as soon as results of the work are availa-
State papers please copy.