Bulletin 229, Diseases of Citrus in Florida


77). Irregularly shaped patches may be formed by the joining
of several individual spots. These spots are light-colored at first
but later turn brown, especially upon exposure to warmer tem-
peratures. They are formed by the breaking down of the outer
portion of the rind containing the oil cells. In this respect they
differ from typical anthracnose spots in which more of the un-
derlying tissue is invaded and broken down. The injury ap-
parently does not extend very far into the spongy tissue beneath
the layer of oil cells and it is only after a long period that any
evidence of discoloration appears in the inner part of the rind,
unless the fruit is invaded by organisms. Although the pulp
of the fruit apparently is uninjured, the affected fruit is very
unsightly and badly pitted fruit would hardly be salable.
 Storage spot is a physiological breakdown of the rind akin
to apple scald in that it apparently is caused by interference
with the normal respiration processes and enzyme activities of
the fruit under storage conditions, particularly poor ventilation.
This spotting is most troublesome on fruit stored at 380F. and
below but, under some conditions, a temperature of even 420F.
and below will induce the breaking down of the tissues. To
avoid this storage trouble, it is recommended that the fruit either
be stored at a temperature of from 420-500F., or that it be held
at a temperature of 700F. for from one to three weeks to cure
the rind and then stored at a temperature of 320F. Good ven-
tilation and circulation of air will aid in the prevention of this
spotting, not only in cold storage but also in the coloring room
and in storage at ordinary temperatures.
 Pronounced cases of this pitting and brown spotting frequent-
ly develop on oranges that have been held in the coloring room
with improper ventilation (Fig. 78). The trouble has also been
observed to develop on apparently sound oranges that were
picked and held for some time at ordinary temperatures. While
it is likely that the breaking down of the rind in some cases
originated with imperceptible injuries, the frequent occurrence
of this trouble on obviously uninjured fruit indicates that a
purely physiological breakdown is responsible. A slight pitting
of the rind without any discoloration, however, has been observ-
ed to occur late in the season on early and midseason varieties
of citrus fruit while still on the trees, the trouble occurring most
frequently on the upper half of the fruit. This appears to be
a physiological breakdown of the rind associated with over-