Bulletin 229, Diseases of Citrus in Florida


the closely interwoven vegetative filaments of the fungus. Spores
are borne on the filaments and, through the agency of wind, are
carried from tree to tree. Sooty mold is entirely superficial and
may be rubbed off or often pulled loose from the leaf (Fig. 48).
With age, under very dry conditions or where the trees have
been sprayed with oil emulsion or soap solution, it may become
broken up and detached and blown off in fragments by the wind.
 When sooty mold follows the attacks of whiteflies or other
honeydew-excreting insects occurring in enormous numbers on
citrus trees, it prevents
the sunlight from reach-
ing the leaves and inter-
feres greatly with the
normal functioning of
the leaves. It may seri-
ously retard the growth
and cause light blooming
and fruiting. Fruits that
are covered with the fun-
gus a r e retarded in
ripening, usually color
unevenly, and are often
small in size.
 Since sooty mold oc-
curs merely as a sapro-
phyte in the honeydew
excreted by certain in-
sects, especially white-
flies, aphids, and scale
insects, it can be pre-
vented b y controlling
these insects. This may
be done either by the use
of natural enemies, such
a s entomogenous fungi
and insect parasites, or
spraying with oil emul-
sion. T h e latter will
prove very effective in Fig. 48.-Sooty mold on grapefruit leaf.
cleaning the trees of The light areas show where the film of
 closely interwoven fungus filaments has
 sooty mold. been partly detached.