38 
FLORIDA STATE HORTICULTURAL SOCIETY 
I do not wish to infer that by building 
up or improving the vigor of the tree that 
diseases will be entirely avoided by this 
method. This is only the first step in the 
campaign of prevention. The coming 
citrus crop should be one of value and 
whether it is mainly a crop of culls or 
bright fruit will depend largely on how 
well the trees have been cared for and how 
well diseases have been kept under con¬ 
trol. 
There are three diseases that should be 
kept prominently in mind during the 
present season. They are: Citrus Scab, 
Melanose and Withertip. These will un¬ 
doubtedly give more or less trouble in 
all citrus groves and in many cases we 
may expect serious injury unless active 
means are taken for their prevention. 
Scab may be considered more from the 
viewpoint of eradication and the ma¬ 
jor part of this work should have been 
accomplished sometime ago. In regard 
to Melanose and Withertip, the chief task 
will be prevention and this work should 
not be further delayed. 
CITRUS SCAB. 
(Cladosporium citri Mass.) 
Citrus Scab is one of our common and 
well known fungus diseases. It is wide¬ 
ly distributed over the State and fre¬ 
quently causes serious loss to the grape¬ 
fruit crop. In this connection is has be¬ 
come a serious problem within the last 
few years. The disease attacks young 
succulent tissue, such as leaves, stems, 
and fruits, forming characteristic scab¬ 
like masses or warty projections that are 
easily distinguished from injuries pro¬ 
duced by other agencies. In these inju¬ 
ries produced on leaves and stem, the fun¬ 
gus survives from one season to the next 
and in trees affected with Scab, there is 
always an abundance of the fungus pres¬ 
ent to cause a spread of the disease when 
favorable conditions appear. The age of 
the tissue and weather conditions have an 
important bearing on the development of 
Citrus Scab. Only the young tender 
growth is affected and then only in the 
presence of a liberal supply of moisture. 
Even in groves badly infected with the dis¬ 
ease, where new growth develops during 
periods of dry weather, little or no scab 
will be observed. Thus the disease is 
more or less sporadic in its occurrence, 
becoming very destructive in some seasons 
and in others giving little or no trouble. 
The period in which young growth is 
susceptible to attacks of scab is rather 
limited, probably not exceeding over six 
weeks. Leaves and twigs may become in¬ 
fected from the time they appear until the 
growth begins to harden. Fruits are 
probably susceptible from the time the 
bloom drops until six weeks or two 
months later. By protecting the foliage 
and fruits through the critical period with 
some good fungicide, the injury from scab 
may be largely avoided. 
Probably no more favorable time could 
be found than the present season for the 
complete control or eradication of Citrus 
Scab, especially in those groves where it 
has been troublesome in seasons past. 
Where infected trees have been sufficient¬ 
ly injured by the cold to cause complete 
defoliation, much has already been ac¬ 
complished in the way of eradication. The 
fungus has been largely removed from 
such trees in the fallen leaves and fruits 
