p+ ANT B3OARO
April 1947 -718
United States Department of Agriculture
Agricultural Hesearch Administration
Bureau of Entomology and 1-lant quarantine
INS31CTICIDAL TRIEAI;..,'.5 FORJ THE CC:Hi'RL CF THE
lfiOPEAN COK:; *.",RER I_/
By A. Baker and !i. 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. "'ith the advent of new. materials and more
efficient equipment for their application, the use of insecticides may
eventually become practical even on sweet corn crown 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
most effective sprays that have been found, considering cost and toler-
ance by the corn plants, are preparations of DDT, ground stems of R_-
ania speciosa, and a rotenone powder (either ground derris or cube
root). Finely ground dust mixtures containing not less than 25 percent
of DDT with an inert diluent, such as certain clays, have been used
very effectively in water suspension at the rate of one-half pound of
DDT per 100 gallons of water, plus a suitable spreading agent 2/.
Derris or cube should be used at the rate of 4 pounds of the ground
root, containing approximately 5 percent of rotenone, per 100 gallons
of water plus a suitable spreading agent.
The ground stems of Ryania speciosa should be used at rate of
4 pounds per 100 gallons plus a spreading agent.
l/Excerpt from a forthcoming revision of U. S. Dept. Agr. Farmers'
Bul. 1548, The European Corn Borer: Its Present Status and Methods of
_/Spreaders are sold in powder or liquid form and packa:ed under
various trade names. Ordinary soap powders should not be used because
of their tendency to burn the plants. The only spreading anrts tested
that have 4iven consistently satisfactory results without t plant injury
are the sodium monosulfonate of butylphenylphenol, sold under the trade
name Areskap, and an aromatic monosodiumn sulfonate, sold under the trade
name Ultrawet. uther sprea.ing agents are on the inarket, but the suit-
ability of :u.ost of them for use in sprays fur application to groinn'
corn nas not been determined.
- 2 -
The spreading agent facilitates the penetration of the s-.ray deep
into the whorl and between the leaf sheaths -,:.d the stalk where the
young larvae feed. Thorough treatuiernt of these areas is r.ecessary to
insure that the young borers will be reached.
Caution. DDT is moderately poisonous to warm-blo'i.ej anrLals and
is excreted in small quantities in the milk of animals fed hay or feeds
containing appreciable quantities of it. Chemi.l analyses have shown,
however, that practically no insecticide reaches the kernels inside the
husks of corn treated according to the foi vdnin instructions, and that
roasting ears from such corn may be eaten with complete safety. On the
other hand, light, residues may remain on the leaves, stalks, husks, and
silks. The available evidence indicates that these parts of the plants
may be safely fed to meat animals, provided the DDT is applied to the
crop in strict accordance with the instructions given in this circular.
Because some of the DDT is known to be excreted in milk, plant materials
bearing residues of it should not be fed to aninils that are producing
milk for human consumption, at least until more is known concerr.ing the
hazards resulting from the use of such milk or the products made there-
from as food for man.
How to Mix Sprays
As there is danger of injuring corn by the use of too much spreader,
the quantity of this material should be carefully regulated. To prepare
the spreading agent for mixing with a spray, dissolve 1 pound in 2
quarts of water and then add enough water to make 3 quarts (96 ounces)
of solution. This makes a stock solution of the spre-ider sufficient for
300 gallons of spray.
The procedure for mixing the spray is as follows: (1) Place the
stock spreader solution to a small quantity of water in a container;
(2) add the proper amount of DDT, rotenone cwcder, or Ryania speciosa
to this solution, stirring the mixture until thoroughly wetted; and
(3) add this mixture to the bulk of spray water, stirring it thoroughly.
Smaller quantities of the spray may of course be prepared, but in so
doing care should be taken to use the ingredients in the exact propor-
tions indicated above.
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 of spray required for -ech a, clica-
tion will range from about 100 to 200 jallons per acre, depending on the
stand, size, and variety of corn.
A nozzle delivering a solid cone, rather than a hollow cone or
other type of z: ray, has been found the most satisfactory for
directing the insecticide toward the places .anere young borers are
On corn in the early growth sta es the s. .i-j should be directed
downward into the whorl of leaves. ',hen a power sprayer e.,lipped with
a boom is used, tia nozzles per row of corn should be provided.
After the ears begin to develop, tV.Y two outside nozzles should be
lowered to not more than 1 foot below the center nozzle and tui..e-
slightly inward, 'ie direction of the spray should emnain downward and
toward the ear, to form a band of spray that will thoroughly treat all
places where the borers are f:in-'.
The insecticide should oe constantly agitated in the spraj,,r dur-
ing the application.
Compressed-air spraye-rs of the portable 3-gallon size and the
larer wheelbarrow type have been found useful for spraying in home
gardens and small acreages. Horse-drawn and self-propelled, hi-'h-
clearance boom sprayers have given highly satisfactory control of the
borer in commercial fields of sweet corn,
Dusts containing 5 percent of D)T mixed with talc or pyrophyllite
have 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 ,-ith dusts containing powdered derris or cube root
mixed with one of the diluents mentioned aoove. This mixture should
contain not less than 1 percent of rotenone when applied at the rate of
40 pounds per acre.
Applications to small plantings may oe ;iade with hcid-operated,
bellows or rotary-type i,:plements, fitted with a single extension tube
and nozzle. Power-operated, multi;ie-row dusters are more practical
for larger acreages. They are available in :igh-clearance design and
are equipped to treat four or more rovws with two nozzles per row ad-
justable to various olant parts and heights.
!e! to Apply Sprays and Dusts
The first insecticidal applih ation Ihould be made when the corn
borer eg- masses in the field begin to hatch. Three additional appli-
cations should be .ade at 5-day intervals, since ei,', 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.
I i time when the borer eggs begin to hatch varies from year to
e.:ar, and from field to field. For 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. .,hen hatched eggs are found, or eggs in which the black
heads of worms can be seen, it is time to make the first application.
Equipment and materials should be made ready well in advance of the
time when they are likely to be needed.