Florida Agricultural Experiment Station


in the culling of the fruit since, by reason of the weak places in
the rind, hail-injured fruits are more subject to blue and green
mold decays in transit or on the market.

DISEASES CAUSED BY ALGAE AND LICHENS AND PARA-
 SITIC AND EPIPHYTIC FLOWERING PLANTS
 Citrus trees commonly harbor a great variety of plants, in-
 cluding algae, lichens, mosses, ferns, dodder, Cassytha, and air
 plants. With the exception of the parasitic plants, these mis-
 cellaneous plants are of little or no particular consequence in the
 life of the trees. Most of them are merely attached to the sur-
 face of the bark, although some may penetrate the outer por-
 tion of the bark. The more important of these plants are dis-
 cussed in the following.
 ALGAE
 Citrus trees are sometimes attacked by certain algae, which
constitute one of the lower groups of plant life closely related to
the fungi. While most of the algae inhabit the water and are
not parasitic, a few of them live out of the water and are more
or less parasitic. Other non-parasitic algae sometimes become
abundant on leaves and twigs during rainy periods or in localities
with high air humidities. They usually form a yellowish-green
powdery coating of blotches and do not appear to do any direct
harm to the parts on which they grow.
 One of the partially parasitic algae (Cephaleuros virescens
Kunze), which is widely distributed on a wide range of plants
in tropical and subtropical countries, occurs on citrus and sev-
eral other plants in various parts of Florida. It is especially
widespread and destructive in India and the East Indies, where
it causes the well-known red rust disease of tea bushes.
 This particular alga occasionally attacks the leaves, twigs,
and smaller branches of citrus trees in Florida. On the leaves,
small round spots are produced which may vary from 1/8 to 1/2
inch in diameter and appear on either surface of the leaf (Fig.
95). The spots are raised and do not penetrate through the leaf
tissue. They are reddish-brown or rusty in color when well de-
veloped but may be greenish or greenish-brown at times. Al-
though one of the green algae, the color is imparted by numerous
minute orange-colored, hair-like outgrowths which project per-
pendicular to the vegetative thallus growing over the plant parts.
While young plants lack these hairs, they may be so numerous


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