PRESS BULLETIN No. 82.
Florlde Agricullural Expcrlm nl Slallon.
WHITEFLY CONTROL-INTRODUCING THE FRIENDLY FUNGI.
By E. W. BERGER.
PINNING FUNGUS-BEARING LEAVES.
The leaf-pinning method of introducing the fungus parasites of the cit-
rus whitefly has given excellent results during the warm months of the
year with the Red and Yellow Fungi, and some good starts of the Brown
Fungus have also been obtained. During the cooler months, however,
from October onwards, the writer has not found this method so success-
ful as the spore-spraying method (which was described in Bulletin 88 and
in Press Bulletin 80). This is chiefly (it is believed) due to the absence in
the cool season of the adult whitefly and perhaps other insects, which pre-
sumably aid in the dissemination of the fungus spores. About a dozen fun-
gus-bearing leaves may be pinned to the under surface of the leaves of a
whitefly-infested tree, taking care to pin them where the immature insects,
the adults, or both, are most abundant. The writer has always pinned the
fungus-bearing leaves with the fungus side down, this being their natural
position. The leaf-pinning method is also applicable to the White-fringe
and the Cinnamon Fungi, which were recently described as parasitic upon
Small whitefly-infested trees, having an abundance of a whitefly-destroy-
ing fungus on their leaves, have been temporarily planted by some citrus
growers so that their foliage was in contact with that of the trees into
which it was desired to introduce the fungus. This method of introduc-
ing the fungi (although good) is not so practical as either the spore-spraying
or the leaf-pinning methods, and is much more expensive. .It is applica-
ble to all the fungi which are known to be parasitic on the whitefly.
THE FUNGI LIVE ONLY ON THE WHITEFLY.
These five parasitic fungi, so far as is known, probably live, in a natural
state, only on the immature young of the whitefly (which feed on the under
surface of leaves), so that there would be nothing for them to live on in an
uninfested tree; it is therefore quite obvious that it would be futile to intro-
duce fungus into a tree not infested with whitefly. It is best to wait, before
introducing fungus, until the whitefly (larvae, pupae, or adults) can be
found, at least by the dozen, under many of the leaves of a newly-infested
tree. It is also clear that it would frequently lead to a waste of fungus
and of labor were one to treat every single tree in a grove which Wae just
becoming infested with whitefly, regardless of the amount of whitefly on
March 2, 1908..
WHEN TO INTRODUCE FUNGUS.
"Seed fungus" becomes abundant about midsummer and lasts until mid-
winter and later, although some can generally be obtained at all times. The
best weather conditions for introducing fungus are met with from about
June to the end of August. Since this rainy period is also the time when
seed-fungus is abundant it is the best time in which to introduce fungus. It is
advisable, however, to introduce fungus at any other times when "seed-fungus"
can be obtained, using only the spore-spraying method during the cooler
months, but employing any one of the three methods during the warmer
months or when the adult whiteflies are swarming about the trees.
PLAN OF CAMPAIGN.
The writer's plan of campaign, based upon experiments in the field, is
as follows:-lf a grove is thoroughly infested with whitefly, and sufficient
seed-fungus is available, introduce fungus into all the trees; but if the sup-
ply of seed-fungus is limited, distribute it here and there throughout the grave,
so that there will he a great many centers of infection from which the
fungus can spread. It may be considered advisable to treat only a few
trees in each row with fungus, and it may only be possible to treat some
branches of each of these trees; but any scheme of distribution that will give
the fungi a good chance to spread to all parts of a grove will suffice. Later
on, when more seed-fungus is available, the trees or parts of trees not pre-
viously treated may be attended to. A second, and even a third or fourth
treatment may be given to the trees in order to get the quickest possible
dissemination of fungus. So long as only a few fungus pustules are visible
on those leaves of a tree which bear the most fungus, it will be advisable
to introduce more fungus, especially should an abundance of seed-fungus be
readily available. The greater the amount of fungus growth which is success-
fully started in a grove by artificial means, the more rapid will be the de-
struction of the whitefly, Whiteflies have the habit of congregating on
water-sprouts and other tender growth of citrus, consequently we should
give particular attention to introducing the fungi into such parts of the trees.
The work should be done methodically and not in a haphazard way.
The plan of campaign for a grove just becoming infested with whitefly,
or only infested in part,, would be to introduce fungus into all those trees
sufficiently infested (that is, whitefly by the dozen on the leaves), and
later on into other trees as soon as they become sufficiently infested. Inci-
dentally, the trees may be fertilized a little more heavily.
WHERE TO OBTAIN FUNGUS.
Fungus can probably be obtained at the following places:-Manatee,
Bradentown, Palmetto, Sarasota, Fort Myers, Buckingham, Orlando, Oviedo,
State papers please copy.