Bulletin 229, Diseases of Citrus in Florida


 Lichens are considered harmless so far as any direct injury
produced by their own growth is concerned, but detract greatly
from the well-kept appearance of the trees. They are apt to
grow more abundant on twigs and branches of weak, slow grow-
ing trees than on vigorous, rapidly growing ones. Since the
lichens do not penetrate the bark deeply and establish no true
parasitic relation with the tree, it is supposed that any damage
that they may cause is due to their mechanical interference with
the respiration and transpiration processes which go on through
the lenticels, or breathing pores, of the bark.














 Fig. 97.-Lichens on citrus leaf.
 It is not usually considered necessary to destroy the lichens
on the trunks and branches of trees unless they become excessive
in amount. Their destruction can be accomplished easily by
spraying the affected parts with bordeaux mixture. The lichens
will die within a few days. The best results will be obtained if
the lichens are sprayed when they are dry. They may also be
removed by merely rubbing the bark with a steel bristle brush
after they have become softened by rain.
 DODDER
 Dodder, or love vine (Cuscuta sp.), is a parasitic flowering
 plant that sometimes occurs on citrus trees in Florida, Cali-
 fornia, and the tropics. Dodder has been most troublesome to
 citrus trees in seedbeds and nurseries, but occasionally infests
 trees of considerable size. Only in rare instances has it proved
 troublesome in Florida.
 Dodder is a small, yellowish, vine-like plant that entwines it-