DDT sprays for control of the corn earworm and budworm in sweet corn


Material Information

DDT sprays for control of the corn earworm and budworm in sweet corn
Physical Description:
5 p. : ; 27 cm.
Blanchard, R. A
Douglas, W. A
Wene, George P
United States -- Bureau of Entomology and Plant Quarantine
United States Department of Agriculture, Agricultural Research Administration, Bureau of Entomology and Plant Quarantine
Place of Publication:
Washington, D.C
Publication Date:


Subjects / Keywords:
Helicoverpa armigera -- Control   ( lcsh )
Spotted cucumber beetle -- Control   ( lcsh )
DDT (Insecticide)   ( lcsh )
Spraying and dusting in agriculture   ( lcsh )
federal government publication   ( marcgt )
non-fiction   ( marcgt )


General Note:
Caption title.
General Note:
General Note:
June 1949."
Statement of Responsibility:
by R.A. Blanchard and W.A. Douglas and G.P. Wene.

Record Information

Source Institution:
University of Florida
Rights Management:
All applicable rights reserved by the source institution and holding location.
Resource Identifier:
aleph - 030295155
oclc - 780181026
System ID:

Full Text
June 1949 ;-70

United States Departri-t of A:--iculture
Agricultural Research AcdmT.inistrtion
Bureau of Entomology and Plant C "- tine


By R. A. Blanchard and W. A. Douglas, Di'oision of
Cereal and Forage Insect Investigations,
G. P. Wene, Texas Agricul';i-sl '-.periment Station 2/

The use of sprays for commercial-scale control of the corn earworm
(Heliothis armigera (Fbn.)) is still in the experi.7rrntal stage, but a
progress report isrbeing given at this time for the benefit of sweet
corn growers who may wsh to these et of control.T'; methods
described are based on experiments cordlucted in Illinois, Texas, Miss-
issippi, and Arkansas during the years 1945 to .T948, inclusive.

A large number of insecticides have been tested in spra-.s and dusts.
DDT has given the best control of any that can be '-r-:iased on the mar-
ket at present. TDE has also given sat is.facory c; 0.1ol, but is rated
as somewhat inferior to DDT on the basis of test-: to date. TDE and
other newer insecticides may be found to be equally satisfactory after
further tests. In our experiments none of the insecticides have given
satisfactory control of heavy earworm infestations he applied as dusts.
However, very good control has been obtained with 1, in ;:in'ral oil
solution and in emulsions cont lnr.ing mineral oil.

Application Equipment

Four types of equipment for applying the sprays were used success-
fully--a knapsack sprayer, a paint-spray machine,and two power sprayers,
one with nozzles for hand application and the other with fixed nozzles.

Knapsack Sprayer.-- A small knapsack sprayer was used to apply
both oil solutions and emulsions to individual ears in small-scale tests.
Such a sprayer may be used to treat corn in small fields, but consider-
able labor and time are required to keep the spray pressure at the 35 to
40 pounds which seems to be necessary. It is possible to provide the
desired pressure by means of a small portable pressure tank such as was
used during the war for inflating life rafts. If such a tank is used,
the knapsack sprayer should have an air-intake valve welded on it. An
air-pressure gage is also necessary to keep from adding more air than
the tank will stand. Where it is used to apply emulsions containing oil,

/ Assistance received from D. J. i.McAlexander, farm mnui&a:er for
F. H. Vahlsing, Inc., Elsa, Tex., and 0. B. Wooten and M. E. Bloodworth,
agricultural engineers, respectively, of the Mississippi and Texas
Agricultural Experiment Stations, is gratefully acknowledged.

JUL 14


the liquid must be kept agitated as it is being sprayed; otherwise the
oil and water in the emulsion will separate.

Paint-Spray Machine.-- Another type of equipment used for applying
sprays to individual ears was a small paint-spray machine with a com-
pressor run by a gasoline motor. This outfit operated at 30 pounds'
pressure breaks up the spray well and drives it into the silk mass. The
equipment used in our tests had a quart-size liquid container, but it
might be feasible to use a larger machine, having a large liquid con-
tainer from which several guns are operated at a time. Some means of
agitating the spray, such as a pipe conducting compressed air from the
compressor to the bottom of the spray tank, is necessary where an emul-
sion containing mineral oil is used.

Power Sprayer with Nozzles for Hand Application.-- The spray was
applied to the individual ears with nozzles attached to hoses on a power
sprayer. Each nozzle was equipped with a shut-off valve operated by
hand. The spray outfit was mounted on two automobile wheels and was
pulled between two rows of corn by a mule. A boom mounted above the
corn had outlets for eight 20-foot hoses spaced the same distance apart
as the corn rows, so that eight men could spray the ears in eight rows
as the machine was pulled through the field. The men walked ahead of
the machine, which was operated at a speed slow enough to allow the men
to spray each ear. The machine was operated at a pressure of 100 pounds
per square inch. About 30 acres per day were treated in this manner.

Power Sprayer with Fixed Nozzles.-- Two types of power sprayers
with the nozzles mounted in fixed positions were used, a piston-type
power sprayer and one employing a gear pump to supply pressure. The
piston-type sprayer was suspended between two corn rows below a high-
clearance carriage drawn by one mule. The gear pump sprayer was self-
propelled, with the pump mounted on a high-clearance detasseling machine.
A single gasoline engine served to propel the machine and operate the
gear pump for spraying. The type of sprayer is widely used in spraying
for chemical control of weeds.

Means of agitation are necessary with both machines when emulsions
containing mineral oil are to be sprayed. The piston-type sprayer has
a mechanical agitator. On the machine employing the gear pump, a hose
from the overflow valve on the pump should be run to the bottom of the
spray tank. It is very important, in order to prevent clogging, that a
strainer of 100-mesh brass or copper wire be fastened on the intake into
the pipe line from the tank to the nozzles and that a similar strainer
be coupled into this line. The spray nozzles should also be equipped
with built-in strainers.

In both the machines the spray nozzles were attached to upright
supports between the corn rows. There was one of these supports on each
side of each row. Two pairs of nozzles, one pair 5 inches above the other,
were attached to each support, making four nozzles per row. One nozzle
of each pair was directed at a row on either side of the upright. The
nozzles were set above the ears, 14 inches from the corn stalks, and were
inclined downward to cover the silks and upper parts of the ears with

- 3 -

spray. The upper nozzle of each ,otir was dird ted sl' ;itly forward and
the lower nozzle of each pair slightly backward, tn machines were
operated at 100 pounds' pressure.

Kinds of Sprays SuggeL,1.0

For Hand Application to Individual Ears.-- A solution container 2
pounds of tec-hnicali DDT in'75 gallons of -%ite mineral oil of 50 to 95
seconds Saybolt viscosity can be applied to individual e' w -th knap-
sack sprayers, by men operating nozzles attacherc to a powi .pr: r, or
with a paint-spray gun. An emulsion made from 3 qurts .factory- re-
pared 25-percent emulsifiable DDT concentrate plus C gallons of the
above-described white mineral oil diluted -o 25 '.lIons with water can
also be applied in this manner. 2/ The oil an'. i concentrate are nixed
together and then stirred into the water until a uniform milky-white
liquid is formed. If sufficient agitation is provided by the sp ..-i
machine, the oil and DDT can bo poured directly into the r.-ruired 'amount
of water in the spray tank. Those materials should not be a lied until
after the ears have been fertilized, i.e., not u:til the seTo. .-e
wilted and begun to ,turn brown pt the outer es

Not more than teaspoonful of the oil solution or | teaspoonful of
the emulsion should be applied per ear. Only one -.lication should be
made to each ear. The oil solution penetrate, the _s better than the
emulsion and gives better control of the worm:, but ill cause some lack
of filling at the ear tips. Although the emulslci gives somewhat less
control of the worms, the ears will fill out better at tne tips. Both
will give good control if the materials are carefull, ap ie, as soon as
possible after the ears are fertili-ed.

A nozzle giving a ve-v fine hollow cone of prE-y should be used for
the hand applications. The angle formed by the cone of spray should not
be wider than 50 degrees at 100 pounds' pressure. Otherwise, it will be
difficult to get proper coverag-e of the silks and ear tips. The nozzle
should be held 3 or 4 inches above the ear tips S-Ld cs.e taken-To spray
the entire silk "ai not just one side of the ear. 'o:Mle;a ~ suTiatbTe- or
use with a power sprayer are manufactured by seversJ 1pra;-equipment
companies, but extreme care should be used to select one that does not
put out too large a volume of spray or large droplets. A nozzle with
0,020-inch orifice has been found satisfactory. The nozzle assembly
should be equipped with a lever-type shut-off valve that is easy to oper-
ate with one hand and has a positive cut-off. The same specifications
also apply to the type of paint-spray gun selected, if that method of
application is used.

2/ Emulsifiable concentrates co:aiininr 30 to 34 percent of DDT are
also on the market. Five pints of the 30-percent materials or 4j pints
of the 34-percent concentrate should be used in 25 gallons of the total
spray. The amount of oil remains the same.

- 4 -

Hand applications by the above methods of an emulsion containing
10 percent white mineral oil of 50 to 90 seconds Saybolt viscosity will
give excellent control if two properly timed aplications are made.
The first application should be made before mor.?e '- 25 percent of the
ears are in silk and the second 2 or 3 days later, Experience has shown
that to deter-nine accurately the percentage of ears in silk actual counts
must be made in the field beginning when the first silk appears. The
timing will be about right if the first sray application is made one day
after an average -of 10 percent of the ears are in silk as determined by
counts made in several places in the field. The general formula for the
spray is 3 quarts of 25 percent emulsifiable DDT concentrate plus 22
gallons of white mineral oil diluted to 25 gallons with water. Ears that
have silks as well as shoots which have not yet developed silks should
receive the spray application. The knapsack sprayer, paint-spray gun and
power sprayer have all been used successfully for applying the emulsion
containing 10 percent mineral oil.

For Power Application from Nozzles in Fixed Positions.-- Tests in-
dicate that the emulsion containing 10 percent of white mineral oil of
50 to 90 seconds Saybolt viscosity is best for applications from nozzles
in fixed positions. With this type of equipment two applications should
be made on a carefully planned schedule. If care is exercised to see
that not over 10 percent of mineral oil is put into the spray, no damage
to the corn should result. This is true whether the material is applied
from fixed nozzles on a power sprayer or by hand applications from a
knapsack sprayer, paint-spray gun or from hand nozzles attached to a
power sprayer. The general formula for such a spray is the same as for
the hand applications mentioned above: 3 quarts of 25 percent emulsifi-
able DDT-/ concentrate plus 24 gallons of white mineral oil diluted to
25 gallons with water../ Approximately 25 gallons per acre per applica-
tion should be applied. Spray nozzles with 0.026-inch orifice giving
a flat fan-shaped spray gave excellent results in 1948. However, a
nozzle putting out an equal amount of spray in the form of a hollow cone
might be equally effective. The angle formed by the spray as it comes
from the nozzle should not be over 50 degrees at 100 pounds' pressure.
If the spray comes out at too wide an angle, it will cover too much of
the pTant, thereby lessening the amount reaching the ears.

Fixed Nozzle Spraying for Control of Budworms.-- The earworm and
the fall armyworm (Laphygma frugiperda(A.& S.)) often attack sweet corn
before and during tassel formation. When they infest corn in this way,
they are commonly called budworms. They may injure the plants severely,
and the large larvae may later travel from the tassels to attack the
young ears.

It was found that a single application of emulsion containing DDT
and 5 percent of mineral oil would effectively control such worms. The
material can be applied with a machine on which the nozzles are held in
a fixed position somewhat as already described. However, two nozzles
should be set directly above the plants to shoot downward, and two should
be directed at the ear-bearing sections of the plants. A single nozzle
fixed directly above the plant and one fixed on each side might be suf-
ficient to give control. The formula recommended is 3 quarts of 25-


percent emulsifiable DDT concentrate-2d/and 10 pint' e' white mineral oil
of 50 to 95 seconds Saybolt viscosity, diluted to 25 gallons with water,
A single application made just as damage begins to ": -aneral over the
field should protect the plants and young ears f.-..: damage. This spray
application will not protect the ears after they begin to silk; therefore,
the single or double applications suggested previously for contr.x of
the earworm infestation should be made at the proper time,

Discussion and Precautions

The effects on the plants and ears of the materials tested and
methods of applying them have been'carefully studied. No bad odor or
taste has been detected in repeated trials of sweet corn that had been
treated with the sprays and by the methods described in this paper. Fur-
thermore, no evidence has been found that any of the materials or methods
of application recommended were detrimental to the corn except for some
failure of tip kernels to fill out when an oil solution of ITT was used.
However, it should be pointed out that the materials and methods recom-
mended have not been widely used by growers and should be used with caution.
The strengths of the formulations and the dosages recoriaended should not be
exceeded, for to do so may result in damage to the corn. Emulsifiable
DDT concentrates with strong disagreeable odors should be avoided. Under
no conditions should kerosene or an oil with a kerosene odor be used.

A consideraLle number of samples of the corn that had been treated
with the insecticides suggested in this paper have been analyzed for the
presence of DDT residues. These analyses have shown that the husked
ears are entirely safe for use as food, but that appreciable residues of
DDT may be present on the husks, silks, leaves, and stalks, Although
these residues are not likely to cause acute poisoning of livestock to
which the plants are fed, very small quantities of DDT may be secreted
in the milk and the fatty tissues of such animals. Therefore, the
treated plants should not be fed to dairy animals or to meat animals
that are being finished for slaughter.


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