PRESS BULLETIN No. 115.
Florlda Agricullural Experlmein Sl1aton.
THE WHITEFLY IN APRIL.
BY E. W. BERGER.
INTRODUCING FUNGUS EARLY.
The earliest opportunity in the yeat to introduce the fungus diseases
of the whitefly larvae by the lpore.-praying method will be about two to four
weeks after the adult whiteflies of the spring brood have disappeared. In
about ten days to two or three weeks after this, the eggs they have laid
will have nearly all hatbhed, and lthe young larvae will be abundant beneath
the leaves. This spring brood oftadults generally emerges in March or early
in April, so that the first brood of young larvae will be on the leaves at.
some time in April. To wait, "before introducing fungus, until the whitefly
larvae have advanced into the fourth or fifth stages, may result in partial .
failure, since these older larvae appear to be much more resistant to fungus
diseases than the younger ones.
Arrangements in regard to -upplles of fungus should be made eatly;
For since much of the previous summer's crop of fungus either becomes
badly weathered or peels off during the winter, and very little or no new
fungus develops during that time, it may be difficult to get large quanitieb
readily. ,(For methods of introducing fungus see Bul. 97.)
In groves in which fungus has only spread slightly, as diligent an
effort should be made to spread it as in groves not having any fungus at all.
While the natural agencies will no doubt gradually disseminate it after it
is once there, these should not be alone depended Upon; for it is quite an-
easy matter to spread the fungus artificially and thus aid the natural agen-
cies. If we can get fungus started early, it has the whole summer In
which to grow and spread, and will also furnish seed-fungus for use later
in the season. We should not hesitate to spread fungus at any subsequent
time when young larvae are again present; say during June, July or August,
and even later. The more fungus we sow, the more will grow; and the
'more rapid Will be the destruction of the whitefly.
It sometimes happens that the fungi cannot be applied, or that the
grove needs immediate relief: in such cases it is advisable to reduce the
number of whitefly by spraying with contact insecticides. While it has
generally been recommended that spraying the whitefly with contact in-
secticides should he practiced in winter, observations made upon trees
April 10, ''1909
sprayed In November while most of the larvae were still immature, indicate
that It may be possible to do very effective spraying at any time when
the larvae are young. It would appear, therefore, that the time recommended
for Introducing fungus by the spore-spraying method would likewise be a
good time to spray with contact insecticides. A spraying mixture of suffi-
cient dilution to insure its being harmless to very tender foliage, would be
effective in destroying these tender larvae; whereas even a strong mixture
might be less effective in winter. or at any time when the larvae are well
matured. It is, therefore, suggested that whenever it Is found difficult or
Impossible to obtain fungus with which to Infect the spring brood of
whitefly larvae, the trees should be sprayed with some contact insecticide.
This should reduce the numbers of the whitefly and allow the trees to thrive.
Later in the sea-on, when the young larvae are again abundant, the trees
may be sprayed a second or a third time; or fungus may be introduced.
These suggestions upon summer spraying with insecticides are also made
for the benefit of tho-e who may prefer to experiment with spraying before
trying other measures. By spraying, of course, thorough spraying is meant.
Whale-oll soap, as a prayingg mixture, will probably be the least Injurious
to the fungu diseases of scales and whitefly.
CHINABERRY AND UMBRELLA TREES.
If all Chinaberr. and umbrella trees in a citrus-growing community
have not yet been eradicated, this should not be delayed beyond April. The
reasons why these trees should be destroyed were given in these columns
A STATE LAW.
It I* not generally known to citrus growers that Florida has what is
practically a local option law for the protection of citrus groves and other
orchards against the vhiltiflv and other insect pests and' di-eases. (See
Chapter X111, Statutes of Florida. 1906). This law empowers the county com-
missioner- to appoint a board to carry out its provisions. Any county wish-
ing this law put into effect can have the board appointed when 40 per
cent. of the fruit growers sign a petition to that effect. This board can
compel the destruction of such food plants of the whitefly as Chinaberry rnd,
umbrella trees, and otherwise inaugurate repressive and quarantine meas-
ures naainst the whitefly.
State papers please copy.