PRESS BULLETIN No. 299
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
PRESERVING FUNGUS PARASITES OF WHITEFLY
J. R. WATSON
At the beginning of the rainy season in June, the grower of
citrus fruits should see that there are plenty of the parasitic
fungi, both the red and the brown, in his grove. If they are not
already present, he should spare no effort to introduce them. How-
ever, in June, fungus material is often scarce, while in the fall it
is usually abundant. Therefore, it should be collected at that
time and preserved for future use.
Dr. E. W. Berger, entomologist to the State Plant Board, has
shown that it keeps well in cold storage. The grower having cold
storage facilities should collect a supply of fungus for use next
summer. Collect a quantity of leaves having the beneficial fungi
upon them, and allow them to dry for a week or ten days in an
airy room, out of the rain and direct sunlight. Put the dried
leaves in a tight tin box. Place the box in a cold storage room
where the temperature is usually below 40 degrees F. or in a
refrigerator. Next June this fungus material will be fresh and
bright and capable of germination.
But many growers do not have cold storage facilities. They
may dry the fungus material and keep it in a dry place until
needed. The leaves should be spread in an airy place, out of the
direct sunlight, until they are thoroly dry. They may then be
placed loosely in a box and covered to exclude dust and sunlight.
Such material has been kept from October to the following
August and then produced a "catch", altho a poor one. It is
best to collect it as late as possible in the fall (October or Novem-
ber) and use it as soon as the rainy season sets in, usually June.
The Plant Board is growing two of the whitefly fungi (Red
Aschersonia and Yellow Aschersonia) in pure cultures on sweet
potato and supplying it in a fresh condition to growers at cost. The
Yellow Aschersonia thrives only on Cloudy winged whitefly. This
is undoubtedly the safest way to introduce these fungi into the
November 16, 1918
grove, as there is no danger of introducing any harmful fungus
disease as might be done by bringing leaves into the grove.
Those who wish to obtain any of this material should write to the
State Plant Board, Gainesville, Fla., for further information.
The brown fungus, however, has not been raised on artificial
media and we must depend upon preserved material. As the
brown fungus is much more thoro than the red in its work of
killing out the whitefly, the grower should spare no effort to in-
troduce it and spread it in his grove.
Whether one uses the dried or the pure culture material, the
mode of application is the same. Wash the spores off into water,
strain thru coarse cheese-cloth or fine wire gause to remove all
solid particles, and spray,into the trees. Use a pump that has
never been used for bordeaux or lime-sulphur. Use approx-
imately three or four dozen leaves to a gallon of water. If one
does not get a good catch of the brown fungus in June or July,
he should try again in August, since it is easier to get a catch then.
The brown fungus, tho harder to start is more efficient than the
red. In selecting brown fungus for drying, select leaves having
spores. These are formed on the upper side of the leaves in
rusty-brown, dusty looking areas.
State Papers Please Copy.