82 
FLORIDA STATE HORTICULTURAL SOCIETY 
will have achieved one of the greatest un¬ 
dertakings in the history of plant diseases. 
This will mean a great deal to the state 
of Florida, and will be an object lesson to 
other states. 
Activities against this disease are not 
confined to Florida alone. In some of the 
other States where the disease is found 
our example of complete eradication is 
being followed, and it is to be hoped that 
in the near future citrus canker will'be 
eliminated from the United States. Then 
with the co-operation and support of the 
Federal Government, which is now taking 
an active part in the work, and adequate 
State crop-pest laws, neither citrus canker 
nor any other similar pest will again be 
able to establish itself in Florida. 
NATURE AND SYMPTOMS 
In considering the nature of citrus can¬ 
ker the following features illustrate the 
more prominent characters of the disease. 
It is very infectious and spreads easily 
and rapidly from infected to healthy trees. 
It is capable of infecting all parts of the 
tree at any stage of growth. Canker 
once formed on the tree are persistent 
and do not disappear naturally. The 
disease does not respond to the ordi¬ 
nary methods of control. 
Usually the disease forms a typical spot 
by which it can be easily recognized. 
These spots are generally circular in out¬ 
line, brown in color, very much thickened, 
with one or both surfaces broken, exposing 
an inner mass of spongy dead cells. The 
spots may vary in diameter from one-six¬ 
teenth to one-fourth of an inch. Infec¬ 
tions are most evident on the leaves, young- 
shoots, and fruits; although, as already 
stated, the disease may attack any part of 
the tree and at any stage of growth. 
Fruits, leaves, young shoots, the bark on 
larger branches and trunks, and evep the 
bark on exposed roots, have been collected 
showing infections. The young and ten¬ 
der growth is more susceptible to attacks 
than the old and more matured growth. 
Mature cankers formed in the bark of the 
larger branches and trunks are usually 
more irregular in shape and larger than 
the spots on leaves. The specimens and 
photographs I have at hand will give you 
a better idea of the appearance of the dis¬ 
ease than any written description I may 
attempt. 
VARIETIES ATTACKED 
Practically all the well known spefies 
and varieties of citrus are attacked by the 
disease, with the possible exception of the 
kumquat. So' far, the disease has not 
been reported on the kumquat in Florida. 
It attacks the grapefruit severely, and here 
the growers have suffered the greatest 
loss. Citrus trifoliata is attacked as se¬ 
verely as the grapefruit. This, however, 
is not so important, for if the disease was 
confined to Trifoliata alone, we would 
have a much easier problem to handle. 
While the disease is apparently not so se¬ 
vere on the other citrus varieties, the ef¬ 
fects are injurious enough to warrant our 
taking every precaution to keep the least 
susceptible varieties free from attacks. 
Attacks on the sweet orange mav be mild 
now, but in the course of a few years the 
disease may perhaps become as severe on 
this variety as it is on the grapefruit at 
present. 
