PRESS BULLETIN No. 89.
Florida Agrlcullural Experiment Stallon.
SPRAYING FOR SCALE INSECTS.
BY E. W. BERGER.
SPRAYING, A TEMPORARY EXPEDIENT.
The scale insects of most fruit and many ornamental trees in Florida
usually require but little, if any, treatment with insecticides in order to keep
them in check. Occasionally, however, a few trees, or even a whole grove
or orchard, may become so badly infested before the natural enemies (espe-
cially the fungus parasites) make their appearance and become effective,
that immediate treatment with some insecticide becomes advisable. Such
treatment, however, is regarded by the writer as a temporary expedient
only. Afterwards the fungus parasites (see Press Bulletin 83) should be
introduced as rapidly as possible.
RECOGNIZING SCALE LARVAE.
That a grower should be able to recognize the larvae (young stages)
of scale insects is very important, since it is these larval forms, and not
the adults or eggs, that are most easily killed by spraying solutions. It is
also important that a grower should be able to discover the advent of a
brood of scales, since the best time to spray is when the larvae are most
abundant. Scale insect larvae are just visible to the unaided eye, but only
an acute observer would be able to recognize them, so that the possession of a
good hand magnifier becomes almost a necessity. (See Press Bulletin 88).
With a hand magnifier these larvae appear as small yellowish or whitish
insects, generally crawling about, but sometimes at rest. Later on, when
they attach themselves to the bark, leaves or fruit, and become covered
with a delicate whitish waxy secretion, they are visible to the unaided eye
as minute whitish dots. It is in these two stages (the crawling larva and
the larva just settled down and beginning to be covered with the waxy
secretion) that spraying solutions are most effective as a means of killing
BROODS OF YOUNG SCALES.
Some scale insects produce three and even four broods of larvae during
a season, but others only one or two. It is impossible to state the exact
time at which a certain brood may be expected to appear, since the time
of its appearance depends much upon the season, whether early or late,
and upon the latitude of the place. (Close personal observation, therefore,
becomes all the more necessary.) Some few larvae may appear during
April 18, 1908.
warm days in winter, but more begin to crawl about in February, and a
brood is generally well out some time in March, April, or May. Another
brood will appear some time during May, June or July, and a third brood
in August, September, October or later. The larvae of some scales (the
San Jose scale, for instance) do not come forth in distinct broods, but ap-
pear irregularly, since they are born alive and not hatched from eggs
WHEN TO SPRAY WITH INSECTICIDES.
As previously stated, it is generally best not to employ insecticides at
all, but to depend upon the natural enemies of scale insects to keep them
in check. However, should a tree become so infested with scales that much
of the foliage becomes discolored, many of the leaves falloff, and the limbs
and twigs are literally enclosed in a sheath of scales, it will be necessary
to spray in order to relieve the tree. Whenever an abundance of scale
larvae are crawling about, then is the best time to spray. The writer would
consider one scale larva per square inch of surface an abundance, but he
has seen trees infested with the snow scale, or orange chionaspis, upon which
there were scores of larvae to the square inch. In order to secure the
best results it is necessary to spray several times during the season; that
is, whenever a new brood of scales is seen crawling, in suficient abundance.
A WEAK SOLUTION THE BEST.
A weak spraying solution may be employed, so as not to injure the
tender foliage or the young fruit. Any one of the contact insecticides
may be used; such as soap solutions, tobacco decoction or emulsions of oils.
Even pyrethrum powder would be efficient against these naked larvae.
Spraying solutions containing a fungicide, as well as those that are recom-
mended for both insecticidal and fungicidal purposes should be avoided,
because such solutions would interfere with the fungus parasites of the
scales getting a good start, whether these came naturally or were intro-
duced by artificial means. (For general directions how to mix and apply
contact insecticides, see Bulletin 76.)
State papers please copy.