FLORIDA STATE HORTICULTURAL SOCIETY. 
101 
SCALY BARK DISEASE OF CITRUS. 
By H. S. Fawcett. 
Mr. President , Ladies and Gentlemen: 
Scaly bark, a recently discovered dis¬ 
ease of the orange tree, is becoming a 
serious menace to many growers in that 
part of Hillsboro county which is known 
as the Pinellas peninsula. The year be¬ 
fore last it was estimated that from 35 
to 75 per cent, of the fruit in many old 
groves was injured by the spotting due 
to this disease, and this was in addition 
to the injury to the limbs and trunks by 
the killing of the bark. Last year the 
disease was not so severe on the fruit. 
Scaly bark has been known to the Exper¬ 
iment Station for not more than three 
years, and the serious nature of the dis¬ 
ease has been recognized for scarcely 
more than a year and a half. According 
to the older growers in the Pinellas pen¬ 
insula, however, it has been known there 
to some extent for many years. Whether 
it occurs in any other part of Florida, or 
in any other part of the world, I have as 
yet been unable to determine. 
About a year and a half ago I was del¬ 
egated by the Experiment Station to 
take up, along with other plant disease 
work, the investigation of this trouble; 
in order to find the cause, if possible, 
and also a practical remedy. When I 
first took up the work the older growers 
told me that the disease was thought to 
have originated near Safety Harbor, on 
Old Tampa Bay, in what is known as the 
Phillippi hammock. In following up 
these reports I found that nearly all the 
older groves in which the disease was 
worst could be traced back as coming 
from trees that had first grown in a nurs¬ 
ery owned by Mr. Phillippi. It was in 
a large tree next to this nursery 
as reported by Mr. Phillippi’s grand¬ 
son, that the disease was first noticed 
at about the year i860. These trees had 
been planted about 1840, and were 
twenty years old when the disease was 
first noticed. Just how the disease got 
into the grove and where it came from, 
no one knows. 
As to the varieties affected, I find it is 
only serious on the sweet orange. Grape¬ 
fruit is very resistant. Tangerines are 
almost immune, as is also the Mandarin. 
I found Tangerine trees surrounded by 
diseased sweet orange trees, but could 
find no trace of the disease upon them. 
This disease has three fairly distinct 
appearances on the tree: 
(1) . On the bark of the trunk and 
larger limbs there appear roughened, 
ruptured areas, in which the old bark 
cracks and scales off with more or less 
gumming, and a new bark forms under 
the old; and this again cracks and scales 
off in the same way later on. This ap¬ 
pearance has suggested the name Scaly 
Bark. 
(2) . Another manifestation of the 
disease is apparent on the small branches 
and twigs. Small lemon-colored areas 
on the bark are first noticed. They turn 
reddish-brown, and the bark becomes 
brittle and cracks. They develop quite 
slowly, and scarcely ever appear on wood 
that is less than nine months to one year 
old. New spots form between the old 
ones, until in a year or two 1 the limb be¬ 
comes girdled at some point. As the 
