U.S. DEPARTMENT OF AGRICULTURE. ,
DIVISION OF ENTOMOLOGY.

CircuLar No. 1, Seconp Serres.
ee i

CONDENSED INFORMATION

CONCERNING

SOME OF THE MORE IMPORTANT INSECTICIDES.

PUBLISHED BY AUTHORITY OF THE SECRETARY OF AGRICULTURE.

MAY, 1891.

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“wa UBRARIES LA

UNITED STtaTES DEPARTMENT OF AGRICULTURE,
Division OF ENTOMOLOGY,
Washington, D. C., March 1, 1891.
The following information relative to kerosene emulsion, resin
wash, and arsenical mixtures has been placed in circular form to
enable ready and full reply to letters which are constantly being
received in reference thereto. It is not intended to be a complete
consideration of the question of insecticides, but is drawn up to
meet those questions which experience has shown are most often
asked by correspondents.
Respectfully,
C.0V,. Rims

Entomologist.
(2)

CONDENSED INFORMATION CONCERNING SOME OF THE MORE
VALUABLE INSECTICIDES.

KEROSENE EMULSION.

This insecticide acts by contact and is applicable to all non-mastica-
ting insects (sucking insects, such as the true bugs and especially
plant lice and scale insects) and also to many of the mandibulate in-
sects when the use of arsenites is not advisable. Kerosene emulsion
may be made by means of various emulsifying agents, but the most
satisfactory substances and those most available to the average
farmer and fruit-grower are milk and soapsuds. In each of these
cases the amount of emulsifying agent should be one-half the quan-
tity of kerosene.

One of the most satisfactory formulas is as follows:

Per cent.
Merosane= S455 55) basso n ey eet ie ele ate eh alllons tsp 2 67
Common soap or whale-oil soap.-..-..-----.------- pound.. 4)
UNL Sa I Seer ERs Sane Ses Race, + ga NERD gallon... 1f 33

Heat the solution of soap and add it boiling hot to the kerosene.
Churn the mixture by means of a force pump and spray nozzle for 5 or
10 minutes. The emulsion, if perfect, forms a cream which thickens
upon cooling and should adhere without oiliness to the surface of
glass. For use against scale-insects dilute one part of the emulsion
with nine parts of cold water. For most other insects dilute one part
of the emulsion with fifteen parts of water. For soft insects, like
plant lice, the dilution may be carried to from 20 to 25 parts of water.

The milk emulsion is produced by the same methods as the above.

THE RESIN WASHES.

These insecticides act by contact, and also, in the case of scale-
insects, by forming an impervious coating which effectually smothers
the insects treated. These resin washes vary in efficacy according
to the insect treated. Experience has shown that the best formula
for the Red Scale (Aonidia aurantii Maskell) and its yellow variety
(A. citrinus Coquillett) is as follows:

ee ee 8 SS. ae oe oe ee ee OS a LS
Caustic soda (70 per cent strength) --...-.-/-------.----- 02525. O
ifs] GUL 1 isl a gt eee ae age el oe heehee 3 Cee nce. Ries

VRPENHDE (0a) 0 Eee ik Mae Se he el Bg oe gallons.. 100

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The necessary ingredients are placed in a kettle and a sufficient
quantity of cold water added to cover them; they are then boiled
until dissolved, being occasionally stirred in the meantime, and after the
materials are dissolved the boiling should be continued for about an
hour, and a considerable degree of heat should be employed so as to
keep the preparation in a brisk state of ebullition, cold water being
added in small quantities whenever there are indications of the prepa-
ration boiling over. Too much cold water, however, should not be’
added at one time, or the boiling process will be arrested and thereby
delayed, but by a little practice the operator will learn how much
water to add so as to keep the preparation boiling actively. Stirring
the preparation is quite unnecessary during this stage of the work.
When boiled sufficiently it will assimilate perfectly with water, and
should then be diluted with the proper quantity of cold water, adding
it slowly at first and stirring occasionally during the process. The
undiluted preparation is pale yellowish in color, but by the addition
of water it becomes a very dark brown. Before being sprayed on
the trees it should be strained through a fine wire sieve, or through a
piece of Swiss muslin, and this is usually accomplished when pouring
the liquid into the spraying tank, by means of a strainer placed over
the opening through which the preparation is introduced into the
tank.

The preparing of this compound will be greatly accelerated if the
resin and caustic soda are first pulverized before being placed in the
boiler, but this is quite a difficult task to perform. Both of these sub-
stances are put up in large cakes for the wholesale trade, the resin
being in wooden barrels, each barrel containing a single cake weighing
about 375 pounds, while the caustic soda is put,up in iron drums con-
taining a single cake each, weighing about 800 pounds. The soda is
the most difficult to dissolve, but this could doubtless be obviated by
first dissolving it in cold water and then using the solution as required.
This insecticide may be applied at any time during the growing season.

A stronger wash is required for the San José scale (Aspidiotus per-
miciosus Comstock), and the following formula gives the best results:

Resme ules = Sant te Se rene Soe ier DOLLT CS eens
Caustic godt a (70 F per ea gas Se oe tee ee fe dor ig
Bish oils. 262. eee en pints... 44
Water enough to make._.......-- Seock eee aeeeallonsh 00:

Place all the ineradio eg ina kettle ann cover hs water to a depth
of 4 or 5 inches: boil briskly for about 2 hours or until the com-
pound can be perfectly dissolved with water. When this stage is
reached the kettle should be filled up with water, care being taken not
to chill the wash by adding large quantities of cold water at once. It
may be thus diluted to about 40 gallons, the additional water being
added from time to time as it is used.

This preparation should only be applied during winter or during the .
dormant period; applied in the growing season it will cause the loss of
foliage and fruit.

5

In the application of both these washes a very fine spray is not
essential, as the object is not simply to wet the tree but to thoroughly
coat it over with the compound, and this can be best accomplished by
the use of a rather coarse spray which can be thrown upon the tree
with considerable force.

FOR SUBTERRANEAN INSECTS.

Recent experiments have shown the practical value of the resin
compounds against the Grape Phylloxera; and they will also be apph-
cable to the Apple Root-louse and other underground insects. The
cheapest and at the same time one of the most satisfactory compounds
experimented with is the following:

Caustic soda (77 per cent.)....-/...2.....-------=-----pounds.- 5
SENG, iia Re RC ne GU 1 Be ep Se eas do. 40
Weber bop in aiene cers Sorc nectar aiget ee ec ee peer Lae ery ae ipl gallons.. 50

Dissolve the soda over fire with 4 gallons of water; add the resin,
and after it is dissolved and while boiling add water, slowly, to make
50 gallons of compound. For use dilute to 500 gallons. Excavate
basins about the vines 6 inches deep and about 2 feet in diameter, and
apply to each vine 5 gallons. The results will be more satisfactory if
the treatment is made early in the spring so that the rain of the season
will assist in disseminating the wash about the roots.

The kerosene emulsion made according to the formula given above
is also applicable to certain underground insects in cases where it will
not prove too expensive, as, for instance, the grape phylloxera or where
white grubs are infesting a pipet lawn. It may then be used in the
proportion of 1 part of the emulsion to 15 gallons of water, applied
liberally to the soil, and afterwards washed fore at frequent ical
with large peices of water for several days. This can be done
only where there is plenty of water at hand, but will be found of
ereat value in special cases.

In other cases bisulphide of carbon may be used for specific and
local underground forms. Nests of ants, for instance, may be des-
troyed by pouring an ounce of this substance into several holes, cover-
ing them with a wet blanket for 10 minutes and afterwards exploding
the vapor at the mouth of the holes with a torch. Against Onion,
Cabbage, and Radish maggots this substance may also be used by
punching a hole with a sharp stick at the base of the plant and pouring
in a teaspoonful of the liquid, covering afterwards with earth.

THE ARSENITES: LONDON PURPLE, PARIS GREEN, AND WHITE
ARSENIC.

These poisons are of the greatest service against all mandibulate
insects, as larvae: and beetles, and they furnish the most satisfactory
means of controlling most leaf-feeders, and the best wholesale remedy

6

against the Codling Moth. Caution must be used in applying them on
account of the liability of burning or scalding the foliage.

The poisons should be thoroughly mixed with water at the rate of
from 1 pound to 100—250 gallons water, and applied with a force
pump or hand spray nozzle. In preparing the wash it will be best to
first mix the poison with a small quantity of water, making a thick
batter, and then dilute the latter and add to the reservoir or spray
tank, mixing the whole thoroughly. When freshly mixed, either
London purple or Paris green may be applied to Apple, Plum, and
other fruit trees, except the Peach, at the rate of 1 pound to 150—
200 gallons, the latter amount being recommended for the Plum,
which is somewhat more susceptible to scalding than the Apple.
White arsenic does little if any injury at the rate of 1 pound to 50
gallons of water. As shown,by Mr. Gillette, however, when allowed
to remain for some time (2 weeks or more) in water, the white arsenic
acts with wonderful energy, scalding when used at the rate of 1
pound to 100 gallons from 10 to 90 per cent. of the foliage; the action
of the other arsenites remains practically the same, with, perhaps, a
slight increase in the case of London purple.

With the Peach these poisons, when applied alone, even at the rate
of 1 pound to 300 or more gallons of water, are injurious in their
action, causing the loss of much of the foliage.

By the addition of a little lime to the mixture, London purple and
Paris green may be safely applied, at the rate of 1 pound to 125 to 150
gallons of water, to the Peach or the tenderest foliage, or in much
greater strength to strong foliage, such as that of the Apple or most
shade trees.

Whenever, therefore, the application is made to tender foliage or
when the treating with a strong mixture is desirable, lime water,
milky but not heavy enough to close the nozzle, should be added at
the rate of about 2 gallons to 100 gallons of the poison.

Pure arsenic, however, should never be used with lime, as the latter
ereatly increases its action.

With the Apple, in spraying for the Codling Moth, at least two
applications should be made—the first on the falling of the blossoms,
the apples being about the size of peas, and the second a week or 10
days later; but the poison should never be applied after the fruit
turns down on the stem, on account of the danger of the poison col-
lecting and remaining permanently in the stem cavity.

For the Plum Curculio on the Plum, Cherry, Peach, etc., two or
three applications should be made during the latter part of May and
the first half of June; in the case of most leaf-feeders, spray on the
first indication of their presence.

CAUTION NECESSARY IN THE USE OF THESE INSECTICIDES.

The relative susceptibility of Apple, Plum, and Peach has just been
indicated under the head of arsenical poisons, and these remarks apply

: 7

equally well to the use of the kerosene emulsions. In the case of
other plants thorough experiments are still necessary, and all insecti-
cides should be first used in comparatively high dilution. In general
it may be said that tender, young foliage is more susceptible and
must be carefully treated. Thin-leaved, pilose plants are more
readily injured, while thick-leaved glabrous species are least affected.
Annual plants, such as cabbages and other garden vegetables, are
more susceptible than perennials, but in the case of root crops, such
as beets, turnips, radishes, and potatoes, there is not the same need
of caution as to damage to foliage. Damage to foliage is not shown at
once, and in case of rain following an application another application
should not be made for several days. Fruit trees should not be
sprayed with arsenical poison before the blossoms fall, on account of
the danger of poisoning honey bees.

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