Bulletin 229, Diseases of Citrus in Florida


ordinarily on the dead wood, since spores do not seem to be pro-
duced in the corky specks developing from infections on leaves,
twigs, and fruit. It will thus be seen why the presence of re-
cently dead wood in citrus trees is one of the important factors
in contributing to melanose infection. In Florida, drought, in-
adequate fertilization, root pruning through deep cultivation,


Fig. 3.-Distortion of foliage on young grapefruit shoot as a result of
 severe melanose infection.

scale-insects, and freezes are responsible for the great majority
of the dead wood in citrus trees.
 The fruiting pustules of the fungus causing melanose may be
found at any time of the year but usually are not abundant in
winter. With the advent of spring, innumerable pustules begin
to develop and, about the middle or the latter part of April, they
are found in abundance. At this time many of the pustules are
filled with spores, whereas others may be only in the first stages
of spore development, so that successive crops of spores may be
produced while the growing parts of the trees are still suscept-
ible. The length of time that twigs have been dead has an im-
portant bearing on their production of melanose spores, those
that have been dead but a few months being much more likely