78 
FLORIDA STATE HORTICULTURAL SOCIETY. 
year, additional spots form between the 
old ones, and this may go on for several 
years until the branch is finally girdled 1 at 
some point and killed. 
This formation of rough scaly bark 
is also seen on the trunks of the badly 
diseased trees. As time goes on, the 
trunks present an extremely rough and 
shaggy appearance. Pieces of bark one- 
half inch or more in size are pushed up, 
sometimes over areas of several inches in 
diameter, or a continuous surface of rup¬ 
tured bark is formed. New bark arises 
under the old, and only rarely do dead 
areas on the trunk result from this dis¬ 
ease. The exudation of gum is a usual 
accompaniment. 
On the rind of the fruit the spots de¬ 
velop somewhat similarly to those of the 
small branches. The disease affects only 
the outer portion of the rind. The spots 
start either as rings, like those on the 
small branches, or as round yellowish 
areas. These usually begin to appear on 
the fruit in July and August. As the 
fruit approaches maturity, and while it 
is still green, the rings become sunken 
and brown, because of the entrance of the 
withertip fungus, while their central por¬ 
tions remain green. The fruit then col¬ 
ors rapidly, the portion inside the ring 
sometimes remaining green for a short 
time. The center is finally broken down 
by the withertip fungus, and the whole 
spot becomes brown. Some spots are 
formed which are not ringed. Fruits 
spotted by scaly bark color prematurely, 
and drop before the picking season. Oc¬ 
casionally gummy exudations occur at the 
spots on the fruit. 
Cause —A careful study has been made 
to determine just what the cause is. It 
is now believed that the trouble is due to 
a minute microscopic fungus that makes 
its way through the bark from the out¬ 
side and grows just under the outer cells. 
The disease is quite slow in its develop¬ 
ment. It develops so gradually into its 
destructive form that the grower is scarce¬ 
ly aware of its importance until it has 
been present for several years. 
Remedy —-Experiments for the control 
of the disease have been systematically 
carried on at Bayview for the past two 
years. The nature of the disease and its 
slow development upon the limbs and 
trunks, make the effect of any line of 
treatment slow in showing itself. As the 
development of the disease to its destruc¬ 
tive form is slow, so the recovery of the 
tree after the source of infection is cut 
off requires a long time. We cannot ex¬ 
pect to see the beneficial effect of any 
treatment on the branches in much less 
time than eight to ten months. Twenty 
experiment plots, each receiving different 
treatment, were laid out. These have 
been continuously under observation, and 
from the basis for the remedies which 
are here suggested. 
Top Working —Grapefruit, manda¬ 
rins and tangerines appear to be nearly 
immune to scaly bark, even when sur¬ 
rounded by badly affected sweet orange 
trees. Diseased trees may, therefore, be 
topworked to one of these varieties. At 
first sight this would seem to- be too se¬ 
vere a remedy; but, as a matter of fact, it 
can be carried out without serious loss at 
any one time. This can be done by treat¬ 
ing only alternate rows. In this way the 
untreated trees will be found to produce 
a much larger crop, and this will in a 
