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Copyright 2005, Board of Trustees, University
PRESS BULLETIN 205
UNIVERSITY OF FLORIDA
AGRICULTURAL EXPERIMENT STATION
By J. R. Watson.
Many parts of the State are suffering from a severe infestation of red
spiders, due, perhaps, to the unusually warm and dry weather of the past
month. The pests are very common on citrus and strawberries in some sec-
tions. It is unusual for red spider to be so abundant on strawberries, and
the plants have been greatly damaged, as the vines are now in a tender
The best remedy is sulphur. One may use either free sulphur, or some
of its compounds; and apply it dry, or in the form of a spray. Free sulphur
is one of the best remedies against red spiders, or mites. It is somewhat
slower in its action than some compounds of sulphur, taking often two to
three days or more to do its work, but it remains active for a long time,
frequently two or three weeks, and usually kills the mites in the end. Sul-
phur can be applied dry, and driven into the citrus trees or strawberry beds
by means of a blower or duster. In the strawberry patch it can be applied
by hand, or shaken into the vines through a closely woven cloth or a per-
forated can. (This method would, of course, be very wasteful if used for
the orange trees.)
Sulphur and Lime
It is better to mix three parts of dry sulphur with one part of hydrated
lime. The latter can be purchased, or made by adding 32 pounds (four gal-
lons) of water to each 100 pounds of quicklime. Mix hydrated lime and sul-
phur thoroughly. The best .results will be obtained by applying the dust at
night or in the early morning when the air is quiet and the plants are wet
with dew, as the dust seems to stick better at this time. It works better
when the nights are moist and the days bright and sunny, as under these
Februcaryl 1, 1913
conditions the chemical action of the sulphur takes place more rapidly.
As a spray, one can use from one to five pounds of sulphur to fifty gal-
lons of water.
Whether the grower can use the dust or the spray most economically
will depend on a number of things, including the outfit that he can obtain,
the distance the water must be hauled, and the severity of the infestation, the
spray being a little quicker in its action, particularly in unfavorable weather,
than the dust. The dust method secures a more uniform distribution in
a citrus grove.
Of the compounds of sulphur, lime-sulphur is one of the best for use
in the citrus grove. Use about one gallon to 50 gallons of water. One can
use the commercial product, or mix one's own by using 8 pounds of lime and
8 pounds of sulphur. Cover the lime with about six quarts of water, and
as the mixture becomes heated add the sulphur slowly. When the slaking
is over, quickly cool the mass by pouring cold water into it. The lime sul-
phur is hardly to be recommended for strawberries, especially if in bloom.
A compound that will act quickly is potassium sulphide (liver of sulphur).
One pound of this to 50 gallons of water will prove satisfactory in the straw-
berry patch, especially if from 2 to 5 pounds of flour of sulphur are added.
The Red Spiders
The pests that are doing the most mischief now are the two red spiders,
Tetranychus mytilaspidis, and T. bimaculatus, which are only one-twentieth
of an inch across. The full-grown ones are bright red, and the eggs and
young are yellow, becoming spotted as they approach the adult condition.
They are sucking animals and therefore cannot' be reached by a stomach
poison such as the arsenates. They remain mostly on the under sides of
the leaves, where they make a web. The web is conspicuous in the early
morning, where there is dew on the plants. The red spiders suck the sap
of the leaves, which become dry and incapable of nourishing the plant and
State papers please copy.