'A I E PLANT BOARD
May 1947 E-718 (Revision) I/
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant Quarantine
INSECTICIDAL TREATMENTS FOR THE CONTROL OF THE
EUROPEAN CORN BORER 2/
By W. A. Baker and W. G. Bradley
Division of Cereal and Forage Insect Investigations
Insecticides are coming into rather extensive use for control of
the European corn borer (Pyrausta nubilalis (Hbn.)) in market sweet
corn and hybrid seed corn. With the advent of new materials and more
efficient equipment for their application, the use of insecticides may
eventually become practical even on sweet corn grown for the cannery
and on field corn.
The most consistent control of the European corn borer in market
sweet corn has been obtained through applications of a spray. The
sprays that have been found most effective, considering cost and toler-
ance by the corn plants, are preparations of ground stems of Rania
speciosa, a rotenone powder (either ground derris or cube root), and a
finely ground dust mixture containing not less than 25 percent of DDT
with an inert diluent, such as certain clays.
In order to assure penetration of the spray deep into the whorl
and between the leaf sheaths and the stalk where the young borers feed,
and to obtain satisfactory control, it has been found necessary to
include a spreading agent in the spray mixture. Spreaders are sold in
powder or liquid form and packaged under various trade names. Ordinary
soap powders should not be used because of their tendency to burn the
plants. The only spreading agents tested that have given consistently
satisfactory results without plant injury are the sodium monosulfonate
of butylphenylphenol, sold under the trade name "Areskap," and an aromatic
monosodium sulfonate, sold under the trade name "Ultrawet." Other spread-
ing agents are on the market, but the suitability of most of them for
l/This revision should be substituted for E-718, issued in April
1947. It contains important changes. Please destroy all copies of the
2/Excerpt from a forthcoming revision of the U. S. Dept. Agr.
Farmers' Bul. 1548, The European Corn Borer: Its Present Status and
Methods of Control.
use in sprays for application to growing corn has not been determined.
There is danger of injuring corn by the use of too much spreader. The
use of an excessive quantity of this material should therefore be care-
In ready-prepared water-dispersible powders containing 25 percent
or more of DDT which are now available on the market, a spreading agent
has been added in the correct proportion by the manufacturer or processor.
In using such preparations the directions on the package should be
followed carefully in preparing the final spray and no additional
spreader should be used.
Caution: DDT is moderately poisonous to warm-blooded animals.
Experiments have shown, however, that practically none of it reaches the
kernels inside the husks of corn when they are treated according to the
following instructions, and that roasting ears or mature grain from such
plants may be eaten or fed to livestock with complete safety. On the
other hand, light residues may remain on the leaves, stalks, husks, and
silks. Such evidence as is now available indicates that the DDT residues
left on the plants following the use of this insecticide in strict accord-
ance with directions in this circular will not produce ill effects on
livestock to which such plants are fed. However, some of the DDT may be
excreted in their milk and deposited in the body tissues, especially in
the fat. Therefore, until more information is available on the possible
poison hazards to man from consuming the DDT residues occurring in milk
and meat, the feeding of treated plants or portions thereof to meat or
milk animals cannot be recommended.
There is some evidence to indicate that the use year after year of
DDT on crops in the same field, especially in light soils, may eventually
cause accumulations of it in the soil which may be injurious to certain
crops that may be used in the rotation, such as tomatoes, cucumbers,
How to Mix Sprays
In preparing the spray, a stock spreader solution should be mixed
first. To do this, dissolve 1 pound of the spreader in 2 quarts of
water and then add enough water to make 3 quarts (96 fluid ounces) of
To mix 100 gallons of the spray proceed as follows: (1) Place a
small quantity of water in a container and add 1 quart of the stock
spreader solution; (2) add enough of the DDT powder to make 1 pound of
actual DDT (finely ground dust mixtures containing not less than 25 per-
cent of DDT with an inert diluent, such as certain clays, have been used
very effectively), or 4 pounds of the ground derris or cu.be root, or 4
pounds of ground stems of Ryania speciosa, and stir until the mixture
is uniform and free from lunps; (3) add this mixture to enough water to
make 100 gallons, while stirring thoroughly. Smaller or larger quantities
of the spray may of course be prepared, but in so doing be careful to
use the ingredients in the exact proportions indicated above.
- 3 -
How to Apply the Spray
Enough spray should be applied to penetrate the whorls, leaf
axils, and other protected places where borers feed, and to cause
run-off at the base of the plant. The quantity required for each
application will range from aboat 100 to 200 gallons per acre, depend-
ing on the stand, size, and variety of corn.
A nozzle delivering a solid-cone, rather than a hollow-cone or
other type of spray, has been found the most satisfactory for directing
the insecticide toward the places where young borers are feeding.
On the corn in the early growth stages the spray should be directed
downward into the whorl of leaves. When a power sprayer equipped with
a boom is used, three nozzles per row of corn should be provided.
After the ears begin to develop, the two outside nozzles should be
lowered to not more than 1 foot below the center nozzle and turned
slightly inward. The direction of the spray should remain downward and
toward the ear, so as to treat thoroughly all places where the borers
The insecticide should be constantly agitated in the sprayer during
Compressed-air sprayers of the portable 3-gallon size and the larger
wheelbarrow type have been found useful for spraying in home gardens and
small acreages. Horse-drawn and self-propelled, high-clearance boom
sprayers have given highly satisfactory control of the borer in
commercial fields of sweet corn.
A dust containing 5 percent of DDT mixed with talc or pyrophyllite
has been found to provide a high degree of protection when applied at a
rate per acre of 40 pounds of mixed dust. Satisfactory results have
also been obtained with a dust containing ground stems of Ryania speciosa.,
or powdered derris or cube root, mixed with one of the diluents mentioned
above. Byania should be used at a concentration of 40 to 50 percent in
the mixed dust and the derris or cube mixture should contain not leas than
1 percent of rotenone. Any of these dusts should be applied at the rate
of 40 pounds per acre.
Applications to small plantings may be made with hand-operated
bellows- or rotary-type implements, fitted with a single extension tube
and nozzle. Power-operated, multiple-row dusters are more practical for
larger acr-.ges. They are available in high-clearance design and are
equipped to treat four or more rows with two nozzles per row adjustable
to various plant parts and heights.
UNIVERSITY OF FLORIDA
4 3 1262 09239 1423
When to Apply Sprays and Dusts
The first insecticidal application should be made when the corn
borer egg masses in the field begin to hatch. Three additional appli-
cations should be made at 5-day intervals, since egg laying and hatch-
ing continue during a considerable period, the insecticidal residues
become diluted, and new, unprotected surfaces become exposed through
rapid growth of the plant.
The time when the borer eggs begin to hatch varies from year to
year, and from field to field. 7or this reason the insecticide appli-
cations must be timed by the first hatching within the field to be
treated. Careful and timely observations must therefore be made in
each field. When hatched eggs are found, or when eggs in which the
black heads of worms can be seen, it is time to make the first appli-
cation. Equipment and materials should be made ready well in advance
of the time when they are likely to be needed.