Bulletin 229, Diseases of Citrus in Florida


bark crack loose and slough off. In some cases, the activity of
the disease may appear to be checked for a time but usually is
resumed later. As a rule, the disease continues to spread on
the main crown roots (Fig. 16) and laterally around the base
of the trunk until the tree becomes more or less completely
girdled. The destruction of the bark on the trunk, as a rule,
rarely extends more than 12 to
15 inches above the ground. The
height of the bark lesions above
the ground, however, is by no
means always an index to the
progress of the disease for, since
infection usually starts at some
point beneath the soil, it often
happens that a large part of the
root system may be affected be-
fore there are any visible indi-
cations of the trouble above
ground, other than perhaps the
decline of the top of the tree.
Thus, the root system may be
seriously injured before the
grower is aware that anything is
wrong with the tree.
 After foot rot has progressed
 to the point where the root sys-
 tem or the trunk becomes par- Fig. 16.-Foot rot, showing in-
 tially girdled the effect of the fected root with diseased bark
 cut away.
 disease manifests itself by a
 characteristic and usually rapid decline of the tree. The foliage
 becomes light-yellow and scanty and the leaves subsequently
 developed are much smaller than normal ones and frequently
 present a dull, hard appearance. Declining trees have the ap-
 pearance of suffering from lack of nourishment, which is indeed
 the case on account of the partial girdling. Such trees may con-
 tinue to bear a fair amount of fruit for a time and occasionally,
 just before dying, may produce a large crop of fruit. The fruit,
 as a rule, becomes small in the late stages of decline. In well-
 advanced cases of the disease the leaves often become yellow,
 especially along the midribs, and exhibit the characteristic symp-
 toms of acute starvation. The twigs and smaller branches die