ATE PLANT RflAPD
uguATE s 4 E-785
United States Department of Agriculture
Agricultural Research Administration
Bureau of Entomology and Plant (qarantine
THE TOXIC OR REPELLENT ACTION TO TE 3KBOPIAN OORN BORER OF
CORN PLANTS GOWN IN SOIL TBWA1) WITH VARIOUS COMPOUNDS
By D. D. (Qiestel and R. V. Connin, Division of Cereal and
Forage Insect Investigations, and S. I. Gertler,
Division of Insecticide Investigations
In 1944 experiments were begun in Toledo, Ohio, to determine whether
certain insecticides applied to the soil in corn fields would be absorbed
by the plants and thereby make the plants toxic or repellent to the
European corn borer (Pyransta nubilalis (Hbn.)). The results obtained
through 1949 are reported herein.
Several hundred compounds were tested. Many of them were investi-
gated under code numbers and some have not been decoded. Compounds that
did not show promise in these tests are not listed in this paper. Names
of such compounds will be supplied upon request if they have been decoded.
In the sieving tests insufficient quantities of materials prevented
replication. Though unreplicated tests are not entirely satisfactory and
results may indicate valueless materials as being promising, if any com-
pounds were valuable, high borer populations should be no more likely to
occur in replicated plots than in a single plot. However, replication
without variation of treatment would not assist in more definitely evaluat-
ing a compound. It is felt that further tests at varying dosage rates and
time of application in relation to infestation should be investigated before
such compounds can be said to be worthless as chemotherapeutic agents.
Tests in 1944
On April 27, 1944, 521 materials were each applied to single hills
of corn at time of planting. Pour kernels of Spancross sweet corn and
1 gram or more of a single compound were placed in each hill and covered
shallowly with dirt. Many of these chemicals pre-rented germination of the
corn seed* Others apparently acted as fertilizers, causing the corn to
break through the ground ahead of the rest and to continue early growth at
an accelerated rate. When the plants were approximately 6 inches high,
they were thinned to 2 plants per hill. When in the roasting-ear stage,
all plants were dissected to determine the average number of borers per
Plants treated with 24 of these compounds, when mixed with soil, had
an average of less than 3 borers per plant. Dissections of the plants
showed that in 6 hills there were no borers, 6 averaged 1 borer per plant,
12 averaged 2, 16 averaged 3, 10 averaged 4, and 13 averaged 5. The
remaining hills averaged 6 to 51 borers per plant.
Plants from 20 untreated hills were also dissected. They averaged
3 to 24 borers per plant. The average for all plants, including checks,
was slightly less than 13 borers per plant.
Tests in 1945
Of the 63 most promising materials tested in 1944, 25 were retested
in randomized replicated plots in 1945. These compounds were mixed with
equal parts of kaolin, and at the time of planting on April 12 spproxi-
mately 1 gram of active material was placed with several kernels of corn in
each hill. The corn was thinned to 2 plants, when they were approximately
6 inches high. These two-plant hills were replicated five times for each
Owing to various causes, sometimes including possibly the action of
the chemical itself, more than half the treatments contained fewer than
10 plants at dissection time. Weather conditions early in the spring of
1945 were unfavorable for good germination and for rapid growth of sweet
corn. These conditions and a high population of seed-corn maggots
(Hylema cilicrura (Bond.)) were the chief cause of a poor stand and also
of less uniformity of plant size and vigor than would occur in a more normal
On June 19 at the time the first Naropean corn borer eggs were being
laid and on July 7 near the end of the oviposition period, height measure-
ments of the corn plants were recorded.
On July 24, when the plants were in the roasting-ear stage, all were
dissected and the average number of borers per plant was determined. The
entire plant including tillers was dissected. Table 1 gives the borers
found in each replicate, and the average number of borers per plant for
Borer populations averaged 4.8 to 20.5 per plant in the treated hills
and 13.4 borers in the untreated hills.
In 1945, 156 other compounds were given a preliminary trial. This
test was conducted in the same manner as the foregoing test. Height of
plant and number of borers per plant were recorded. Dissections of the
plants made on July 25 and 26 at roasting-ear stage showed an average
borer population per plant ranging from 0 to 29 for treated plants and
from 6 to 20 for the check plants.
Plants treated with 11 of the compounds showed an average of less
than 3 borers per plant. Two of them--pyrethrum and 4,6-dlnitro-M-tolyl
methyl ether--were given further tests in succeeding years.
Table 1.-Number of borers per plant found at roasting-ear stage in
replicates grown in soil treated with various compounds, 1945
Borers per plant in replicated
Compound No. 1 No. 2 ITo. 3 No. 4 No. 5 plant
2, 5-Xylidene, N-benzylidene-
Acetophenone, 3, 1-dilchloro-
Benzoic acid, p-chloro-
Phenol, 2, 6-dibromo-4'nitro-.
Benzene, alpha, beta-dibromo-
Benzophenone, 4, 4-diamino-
Benzoic acid, o-benzoyl-
Aniline, N-isobutyl-2, .4-
i Two-plant hills unless indicated otherwise.
2/ Single-plant hills.
Tests In 194f6
Eight materials that had snovin promise in tests in previous years
were placed in the hills at tt-e time the corn was planted on April 16b,
1946b. Each material was randomized in five replicate hills. Five grams
of material was placed in each hill. When the corn was approximately
1 foot high, the plants were thinned to 3 per hill.
Qn June 10 observations were made to determine the relative tnrifti-
ness and condition of the plants. Height measurements of the corn plants
were taken on June 13 at the start of oviposition, on June 25, which was
the approximate mid-oviposition date, and on July 8, which was the end of
the oviposition period.
Some of the materials at the 5-gram dosage rate appeared to affect
the corn adversely, even destroying some plants. Both 3,4-dichloroaceto-
phenone ana pnenazine produced an injurious effect, not only killing plants
but stunting the growth of those that did survive. At the end of the
oviposition period, plants growing in soil treated with these two chemicals
were not more than 27 inches high, compared with 38 inches or more for
plants growing in untreated soil and in soil receiving many other treat-
On July 15, when tne corn had reached the roastlng-ear stage, all
plants were dissected and the borers contained in each plant recorded.
Data on the results of the 1946 observations are shown in table 2.
4,6-Dinitro-m-tolyl methyl ether appeared to be the most promising
of the materials tested. The plants were high enough to attract moths
for oviposition, and all 15 plants survived. Both DDT and pyrethrum
appeared to have little effect upon the borer in these field tests.
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Tests in 1947
Tests with DDT, Pyrethrum, and 4,6-Dinitro-m-tolyl methyl ether..-
In the spring of 1947 these three materials were applied to plots repli-
cated four times for each treatment. Each plot was 1 row 15 feet long.
Approximately 1/2 pound of insecticide was mixed with soil in each plot
before the corn was planted. A few days after being planted, the rows
were covered with waxed paper supported by wires in the shape of an
inverted U. The paper were removed when the plants were approximately
8 inches high. The waxed paper was used to promote early germination and
rapid growth and thereby induce heavy oviposition by the European corn
borer moths to provide more reliable tests. The highest populations
observed in the Toledo area in 1947 were found in this experiment.
4,6-Dinitro-e-tclyl methyl ether appeared to affect the plants adversely,
as they were less thrifty than the rest. When the corn plants reached
the roasting-ear stage, they were dissected. Borer populations are shown
in table 3. The plants treated with 4,6-dinitro-m-tolyl methyl ether con-
tained the fewest borers, possibly because of the poor plant growth
resulting from the injurious effect of the chemical. Although all three
compounds materially reduced the numbers of borers, none reduced infesta-
tions enough to offer much promise of being of practical value.
Table 3.-Borer populations per 100 corn plants grown in soil treated
with various compounds, 1947
S Yield of Borer
No. 1 ears population Reduction of Plants
Borer In lin p/ borers in-- borer
Compound ____ Total free plant RI Plant; TZars free
Number Percent Number Number Percent Percent Number
Ether, 4, &.initro-
m-tolyl methyl 118 27.9 893 44o 60.7 51.5 8
DDT, 25 percent 118 6.8 1,3200 535 46.4 41.1 0
Pyrethrum 100 8.0 1,405 620 3S.2 31.7 0
Check 115 0 2,275 908 0
for significance at
odjse of 19 to l: 322 128
E/ Entire plant including tillers.
SAll ears including culls.
Tests with Parathion.- In 1947 tests were also made with parathion.
The first investigations were made in the greenhouse and laboratory with
corn grown in 5-inch flowerpots containing soil that had been mixed with
approximately 2 grams of this material. When the stalk portions of plants
were 10 inches high, sections of leaves and of stalks were placed in glass
test tubes each containing two egg masses in the "blackhead" stage which
Just precedes hatching. The leaves were cut into 1-inch sections, rolled
into a small coil, and inserted into the tubes. The sections of stalk were
partially split before being placed in the tubes to permit entrance of
larvae. A cotton-filled cloth stopper was used to close the mouth of the
tube. Test periods ran for 48 hours, during which time many observations
were made without the larvae being disturbed. At the end of the test a
record was made of dead and living larvae and the amount of feeding. This
procedure will be referred to as the standard laboratory technique elsewhere
in this paper. All the European corn borers feeding on these corn plants
were killed in less than 24 hours.
It was suggested that the compound was giving off gases that were
absorbed by the wax on the corn leaves and that the larvae might have been
killed by ftunigation. Newly hatched European corn borer larvae and second
and third instars of the fall armyworm (La gma frugiperda (A. & S.)) were
therefore placed in small glass dishes together with untreated corn leaves
for food, and the dishes inverted on soil that had been heavily treated
with the compound. After 72 hours of exposure the mortality was no higher
Other fall anrmyworm larvae were placed on a 20-mesh wire screen over
50-ml. open dishes each containing a gram of the compound. The larvae were
confined on the screen by inverting a similar dish over them. These con-
tainers were placed in a greenhouse for 24 hours, during which time
mortality was no higher than normal.
Tests were conducted in the greenhouse and laboratory by the standard
technique to determine the period during which parathion was toxic in the
corn plants. When the compound was mixed with the soil at the time of
planting, evidence of toxicity began to appear on the l1th day after plant-
ing. The peak of toxicity was reached on the 21st day, and by the 24th day
most of the toxicity had been lost.
Corn plants 8 inches high, growing in flowerpots in the greenhouse,
were side-dressed with a water suspension of parathion. On the 2nd day
thereafter the leaves began to show toxicity to first-instar larvae and by
the 5th day complete mortality was obtained. After the 8th day there was
a rapid drop in mortality, mand on succeeding days no more than 13 percent
mortality was observed in any tests conducted with the leaves. Stems taken
from these plants caused 90 percent mortality on the 3rd day after treat-
ment. Complete mortality was observed on the 5th day and continued until
after the 13th day.
UNIVERSITY OF FLORIDA
I I11111 I0iI IIIII
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