PRESS BULLETIN No. 80.
Florida Agricultural Experiment Station.
WHITEFLY CONTROL,-SPRAYING WITH FUNGUS SPORES.
BY E. W. BERGER.
THE PARASITIC FUNGI.
It is now generally well known among the citrus growers of this State
that there are several fungi which live parasitically upon the immature stages
(the larvae and pupae) of the whitefly (Aleyrodes citri), and that, as these
fungi become well established in a grove infested by whiteflies, they de-
stroy these insects by the million. The best known of these fungi are the
Red Fungus, the Yellow Fungus, and the Brown Fungus. Three others, not
so well known, are the Red-headed Scale Fungus, the White-fringe Fungus,
and the Cinnamon Fungus. The last two have only recently been described
by Prof. H. S. Fawcett of this Station, in Press Bulletins 68 and 76 re-
spectively; and their discovery being relatively recent we are not so well
prepared to make recommendations, either as to their efficiency in reducing
the whitefly, or as to the best methods for introducing them. The Red-
headed Scale Fungus, so efficient in reducing scale insects in Florida, has
only rarely been observed upon any of the young stages of the whitefly, and
so will receive no further mention here.
PREPARATION OF SPORE-CONTAINING LIQUID.
The following description of the spore-spraying method for introducing
the fungi is based mainly upon experiments with the Red and the Yellow
Fungi, and the method was apparently first successfully employed by the
writer. It is considered the preferable method, and is probably applicable
to all the fungi mentioned, excepting perhaps the Brown Fungus. Experi-
ments so far indicate that this method can be employed during any month
of the year, although a better infection with fungus may generally be ex-
pected during the warmer months. The spores or germs (which take the
place of seeds in fungi) are washed out of the fungus by means of water.
Use about forty of the bright red or bright yellow pustules of the fungus to
a pint of water. This will be about the same as one or two fungus-bearing
leaves to a quart of water. More fungus may be used, but the amount indi-
cated has been found to give good results. Soak and wash the fungus
(leaves and all) for ten or fifteen minutes, and strain through cheese-cloth
or fine wire gauze.
SPRAYING AND SPRAYERS.
Spray the mixture of spores and water on the under surface of the
whitefly-infested leaves. Look well to the newer growth, and if the larvae
February 5, 1908.
and pupae, or the adult flies, or all three, are abundant there, spray the
parts thoroughly. If the supply of seed-fungus is limited, spray only the
worst infested twigs and branches, for the fungus will infect some of the
larvae there, and the adults maturing from those not infected, together
with other adults migrating there, will carry the fungus spores to other
parts of the tree and to other trees. Use a new spraying outfit, preferably
one of the Compressed Air Sprayer type (3 or 4 gallons capacity), with
little or no copper or brass about it. Do not use an outfit previouslyused for
spraying Bordeaux or other strong fungicide, since the small amount of
fungicide left in the machine may kill the spores. An old spraying outfit
which has been previously used only for soap solutions or oil emulsions may be
employed, but it should be well washed out with water. A larger spraying
machine mounted on a barrel may be used when many acres of trees are to be
sprayed, and when an abundance of fungus is available. Use a nozzle pro-
ducing a very fine spray, and thoroughly wet the leaves just to the drip-
ping point. It requires about three weeks for the Red and Yellow Fungi to
make a visible growth.
A modification of the spore-spraying method, recently brought to the
writer's attention, consists in flirting the liquid against the under surface
of the leaves by means of a tin cup. A wisp-broom may also be employed,
or a bunch of small twigs dipped into the liquid. It will not be necessary
to strain the liquid when it is intended to be applied in this manner.
THE BROWN FUNGUS.
The spraying method is probably not generally applicable for intro-
ducing the Brown Fungus, of which the spores are at present unknown.
This fungus has, however, been well started several times by using this
method. If it is desired to employ the spraying method for introducing
the Brown Fungus, it is advised to scour the fungus off the leaves by means
of a little sand and water, using the resulting mixture of fungus particles
and water as a spray. Strain the liquid if necessary. Use about the same
relative quantities of fungus and water as recommended for the Red and
State papers please copy.