Bulletin 229, Diseases of Citrus in Florida


mains attached at the margin for a time. In some cases the dis-
ease may remain quiescent for a time and later break out anew
beyond the edge of the old area. In the well advanced cases of
this type of the disease the bark acquires a scaly, ulcerated ap-
pearance which may involve considerable portions of the trunk
or branch (Fig. 27). Gum may exude from the gumming areas
more or less continuously or the gumming may cease for a time


and much of the old
exuded gum may be
washed a wa y by
rains. In the latter
case there is left only
a scaly appearance
which may be mis-
taken for psorosis by
those not especially
familiar with these
respective diseases.
I n gummosis, how-
ever, the lesions rare-
ly extend around the
trunk or limb in
band-like fashion, as
is commonly the case
with psorosis. In
severe, or long-stand-
ing, cases of gummo-
sis the bark over por-
tions of the affected
area dies to the wood
and the wood itself
will be found to have
been invaded and
discolored. When this
stage is reached, the
affected limb or trunk


Fig. 26.-Portion of grapefruit trunk with early
 stage of gummosis (just above bud union)
 treated by scraping off the outer, dark part
 of the bark over the diseased portion. Note
 cracks in the bark from which gum has been
 S.
 ii















Fig. 26.--Portion of grapefruit trunk with early
 stage of gummosis (just above bud union)
 treated by scraping off the outer, dark part
 of the bark over the diseased portion. Note
 cracks in the bark from which gum has been
 exuding, and the discoloration of the bark
 starting about the older cracks above.


may die from girdling.


 Cross sections of trunks or branches on which gummosis has
been developing for a number of years invariably show a series
of lines of compactly grouped gum canals in the outer portion
of the stem, as in psorosis (Fig. 31), scaly bark and other citrus
diseases characterized by gum formation. These lines of gum