Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations

1959 European corn borer control with granular formulations of endrin, heptachlor, and toxaphene Mahlon Lowell Fairchild Iowa State University

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Recommended Citation Fairchild, Mahlon Lowell, "European corn borer control with granular formulations of endrin, heptachlor, and toxaphene " (1959). Retrospective Theses and Dissertations. 2152. https://lib.dr.iastate.edu/rtd/2152

This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. EUROPEAN CORN BORER CONTROL WITH GRANULAR

FORMULATIONS OF ENDRIN, HEPTACHLOR, AND TOXAPHENE

by

MaliIon Lowell Fairchild

A Dissertation Submitted to the

Graduate Faculty in Partial Fulfillment of

The Requirements for the Degree of

DOCTOR OF PHILOSOPHY

Major Subject: Entomology

Approved:

Signature was redacted for privacy.

Signature was redacted for privacy.

Heati of Major department

Signature was redacted for privacy.

Iowa State Col 1ege

Ames, Iowa

1959 I I

TABLE OF CONTENTS

INTRODUCTION

REVIEW OF LITERATURE

METHODS AND PROCEDURE

DISCUSSION AND RESULTS

SUMMARY AND CONCLUSIONS

LITERATURE CITED

ACKNOWLEDGMENTS

APPENDIX ]

INTRODUCTION

The European corn borer (Pyrausta nubi la 1 is (libn. ) ) was first re­

ported in this country by VinaI (1917). He suggested that it might have

been imported in broomcorn from Europe. Since then it has moved west­

ward and southward until now it covers a major part of the corn growing area in the United States and Canada and has become one of the major

economic pests on corn.

Bradley (1952) reported that the corn borer caused an estimated loss of 314,000,000 bushels of dent corn in 1D'lD alone. Such sizeable losses have necessitated the development of control measures to keep this pest in check. Many insecticides have been tested and recommended for duropcan corn borer control. The first insecticides suggested were the inorganic

insecticides such as the arsenical and fluorine compounds. These were re­ placed by rotenone, nicotine tannate, and ryania. ..'ith the advent of the chlorinated hydrocarbons, DDT was added to the list.

In spite of the progress made in the development of insecticides for use against the corn borer, there is a need for continuing research in this area. The materials recommended when the work was started gave er­ ratic control or left undesirable residues on the corn stover. Therefore, the purpose of this project was to test various rates of granular endrin, hep tachlor, and toxaphene in a search for an insecticide which would con­ sistently give satisfactory control without leaving undesirable residues. 2

REVIEW OF LITERATURE

History of Insecticides

Entomologists have tested many types of insecticides for control of

the European corn borer. Some of the early work was reported by Worth!ey

and Caffrey (1927). Investigations from 1918 to 1926 proved that appli­

cations of insecticides were ineffective in protecting growing corn or

other plants from injury by the European corn borer. These workers tested

various rates and formulations of the following insecticides : lead arsen­

ate, magnesium arsenate, calcium arsenate, nicotine, hydrated lime, and

sulfur. In addition to the attempt to kill the larvae during the period

of establishment, attempts were made in 1925 to kill them in the period of hibernation.

Both laboratory and field experiments of a preliminary nature were conducted on insecticides for European corn borer control and reported by

Huber £t aj_. (1928). The laboratory work was designed to determine the

toxicity of the various dusts to the newly-hatched larvae. In the field

80 percent sodium fluosi1icate was applied at 10 pounds of dust per acre at five-day intervals until six treatments had been made. Final infesta­

tion and borer population counts were made in the fall. These counts showed a reduction of 83 percent in the number of plants infested. Borer population was reduced 58 percent on infested plants by the insecticide treatment.

A number of insecticides were tested by Batchelder and Questel (1930-

Neither acid lead arsenate nor any oil emulsion investigated gave satis­ factory control under field conditions when used a 1 one. Insecticides in­

volving the use of nicotine and pyrethrum as well as several other ma­

terials of the contact insecticide type were not found practical for use

against the European corn borer.

Simanton eit aj_. (1331) round that lead arsenate did not cause a high mortality unless applied in excessive quantities. Calcium arsenate was

no better than the lead arsenate. Some samples of barium fluosi1icate were very toxic to corn while others were not. Mos11 y the kill was good but the corn was more or less injured. Calcium fluosil icate consistently gave satisfactory kills with a minimum of corn injury. Consistent high kills were obtained with sodium fluosilicate but the corn was seriously injured. Nicotine was not sufficiently toxic to justify its use. Thir­

teen fluorine compounds tested in 1330 gave satisfactory kill.

According to Ficht (1333), certain insecticides were tested from 1923 to 1932 to determine their value for curopean corn borer control. Barium fluosi!icate, calcium fluos!licate, and sodium fluosilicate were tested.

Considerable phytotoxicity was observed after application of barium fluo- silicate. Calcium fluosilicate also had a tendency to injure the plants but was considered as one of the most satisfactory insecticides for corn borer control up to that date. Acid lead arsenate in combination with oil emulsions gave satisfactory control and little plant injury. Mydrated lime and talc were used as barriers to young larvae without success.

Hicotine and pyrethrum used a 1 one and with derris gave unsatisfactory rcsu1ts.

Of the materials tested by Turner (193-0 two insecticides were proven 4

to be outstanding and a third slightly less effective for corn borer con­

trol. Pure ground derris root (4 percent rotenone) and phenothiazine

(thio-diphenyl-amine) used in suspension at the rate of 2 pounds in 50

gallons of water with a suitable spreader were very effective. From

sprayed plots 85 percent of the ears were borer free whereas on unsprayed

plots only 36 percent of the ears were borer free. Tank mixed nicotine

tannate was somewhat less effective for about 77 percent of the ears from

sprayed plants were free from borers.

Baker and Oues tel (1939) studied the effectiveness of fixed nicotine

preparations, fluorine compounds, phenoth iza ine and derris in spray and

dust formulations. Derris and the fluorine compounds provided a high de­

gree of protection when used as sprays in a treatment schedule of four ap­ plications spaced at five-day intervals. The fluorine compounds caused more or - Jess injury to the corn plants which made their use undesirable.

A series of tests with various insecticides were conducted by Beard and Turner (1942). Dual fixed nicotine containing 4 percent nicotine was

consistently more effective in controlling the European corn borer than dust containing 1 percent rotenone in the form of pure ground derris root.

Dust made by impregnating inert material with extract of pure ground derris

root or pyrethrum flowers was not significantly less effective than dust prepared by mixing ground root of derris with the carrier.

Results of preliminary laboratory and field tests performed by Questel

(1944) at Toledo, Ohio in 1943 indicated DDT to be the most promising sub­ stitute for ground derris spray thus far tested for control of the European corn borer in early market sweet corn. It gave relatively high reduction 5

of borers in both ears and plants without injury to the corn.

Batchelder and Questel (1945) conducted experiments in sweet corn

near Toledo, Ohio to determine dosage requirements and effectiveness of

DDT as an insecticide for control of the first brood of the European corn

borer. Four applications of dusts containing 0.75, 1.5, 3.0, and 6.0 per­

cent of DDT in pyrophy11i te were made 5 to 7 days apart in dosages of 0.3,

0.6, 1.2, and 2.4 pounds per acre. Borer reduction increased with each

increase in the dosage rate and at the highest rate provided 95 percent

reduction.

Ryan ia was tested by Pepper and Carruth (1945) against the European

corn borer in 1943 and 1944 under field conditions in New Jersey and New

York. In preliminary tests in New Jersey in 1943 the corn borer control

accomplished was considered the most effective ever obtained up to that

time. When the normal application schedule (four to five insecticide

treatments at five-day intervals) was modified by reducing the number of

treatments and lengthening the interval between treatments, satisfactory

results were obtained. Good control was obtained when 20 to 35 pounds of

a 50 percent ryania dust was applied.

After experimenting with DDT dust and spray preparations against both hibernating and actively feeding larvae of the European corn borer,

Questel (1945) suggested that the percentage of DDT may have less bear­

ing on the effectiveness of the dusts and sprays than some other factors perhaps related to the physical and chemical character of the diluent.

Hibernating larvae thoroughly coated with a powder containing 10.8 percent of DDT in pyrophy11i te or with 50 percent DDT with an absorbent clay were b

all killed within three days, whereas very few of those coated with

coarsely ground undiluted DDT or powders containing 50 percent DDT micro- pulverized with fibrous talc were killed.

Several new insecticides were tested by Decker _et _a_L (1947) in the

field in l946. None of those tested showed promise in replacing DDT or ryania. Toxaphene gave fairly good control but rothane and BMC were definitely inferior and metho;;y~DDT was practical 1 y ineffective.

Apple and Decker (1343) reported on experiences in 194C, 1947, and

1343 with insect ici da 1 dusts for corn borer control on canning corn.

Their results showed 40 percent ryania at 25 pounds per acre to be the most effective treatment. Five percent DDT was found to be more effective than equal concentrations of DDT, methoxychlor, toxaphene, and 1 percent rotenone.

Artificially infested single-plant plots were used by Cutkomp and

Hoi daway (1950) to test insecticides. V/ettable-powder heptachlor at 1 pound per 100 gallons of spray applied at about 30 gallons per acre re­ duced the population 77 percent over the untreated control. A 93 percent wettab1e DDT powder formulation at the same rate gave 40 percent reduction while 75 percent wettable powder DDT gave 1j percent reduction. In the same test applications of rotenone at 0.25 pound and ryania at 6 pounds per acre resulted in 20 and 3 percent reduction, respectively.

During the 1350 season, Questel and Brindley (1953) screened a number of compounds in small plots. Materials were applied to the whorl of corn plants in sufficient quantities to reach all points where borers usually feed. Ryan ia at 3.6 pounds per 100 gallons, heptachlor at 1 pound, rote- 7

none at 0.2 pound, and DDT at 1 pound gave 94, 93, 89, and 98 percent re­

duction respectively. In similar tests in 1951 sprays were mixed and

applied at 120 gallons per acre. DDT wettable powder at 1.2 pounds, DDT

emulsifiable concentrate at 0.3 pound, endrin wettable powder at 0.48

pound, heptachlor wettable powder at 1.2 pound, endrin emulsi fiable con­

centrate at 0.3 pound, ryania wettable powder at 4.8 pounds, and penta-

chlorophenol at 0.6 pound per acre gave 9b, 96, 100, 100, 96, 94, and 67

percent reduction, respectively.

Farrar (1953) was the first person to report the use of a granulated

type insecticide for control of any insect on corn. Late corn heavily

infested with corn earworm in the whorl stage was treated with 5 percent

granular dieldrin and 25 percent granular toxaphene. Both insecticides

completely eliminated the infestation in 48 hours. Farrar reported that

equipment designed for applying conventional dusts may be modified to apply

granular insecticides. He suggested that this formulation might be adapt­ able in the control of insects with specialized problems such as the

European corn borer.

According to Cox et al. (1956a) there was no difference between gran­ ular formulations of EPN at 0.1 pound per acre, heptachlor at 1.5 pounds, and DDT at 1 pound for first-brood corn borer control in 1953. Likewise

there was no difference between these three toxicants and ma lath ion in

1954, although DDT and heptachlor gave slightly better numerical borer re­ duction.

Cox e_t aj_. (1956b) experimented in 1955 to test the effectiveness of

14 insecticides in granular formulation. Endrin at 0.4 pound, heptachlor 8 at 1.5 pounds, aldrin at 1 pound, and dieldrin at 0.4 pound gave better

European corn borer control than DDT at 1.5 pounds per acre. The DDT treatment was only slightly better than that with granular toxaphene at 2 pounds per acre. Granular DDT at 1.5 pounds per acre was just as effec­ tive as DDT emulsion spray .at the same rate.

Lovely et_ aj_. (1956) applied 7.5 percent granular DDT at 20 pounds per acre with six different granular applicators. They could not show any significant difference between the number of surviving borers in the plots treated with the different machines.

In a test on sweet corn in 1956, Gould and Wilson (1957) applied various sprays and granular insecticides on June 25. Dissections made on

July 2, 9, and 16 in this experiment showed DDT spray at 1.5 pounds per acre and granular formulations of DDT at 1.0 pound, endrin at 0.2 pound, and heptachlor at 0.5 pound all gave excellent control of the first gener­ ation in field corn. The reductions with these treatments ranged from 79 to 95 percent.

Residues

Batchelder and Questel (1931) pointed out the residue problems after treatment with insecticides for European corn borer control. They state

"Use of corn as silage and the practice of feeding out green corn stalks to livestock introduced a minor problem in insecticide practice. Only a highly volatile material could be employed under such circumstances."

Some of the earlier work on DDT residue after spraying for corn borer control was reported by Decker et al. (1947). Residues on corn 9

foliage apparently weather rapidly at first and more slowly thereafter.

Residues were greatest on the foliage and practically non-existent on the

kernels. The levels of residues were such that they may have some bear­

ing on feeding of crop remnants to cattle.

Fa hey et a_l_. (1953) conducted experiments in 1949, 1950, and 1951 to

study the magnitude of DDT residues on corn plants after dust and spray

treatments for European corn borer control. The effects of spray volumes,

spray pressures, nozzle arrangements, formulations, number of applications, and distribution of DDT on the corn plants were compared. DDT dust at 2 pounds and spray at 1.5 pounds per acre were compared. Dusts gave lower deposits than wettable powder sprays and the greatest deposits resulted w.ith emulsion sprays. With all three formulations the greatest amount of residue in parts per million was found on the leaf tips, followed in order of magnitude by the leaf base, whorl leaves, and stalk. Young corn plants in which the ratio of height to weight is high retained larger residues than older plants in which the ratio is lower. Corn kernels treated with two applications of DDT spray contained no DDT either on the surface or within the kernels. When corn plants with residues of 41 p.p.m. were en­ siled, the silage contained from 12 to 34 p.p.m. of DDT. Milk from cows fed this silage contained from 0.6 to 3-8 p.p.m. of DDT.

The effect of pasturing steers on corn stover in fields treated with

DDT was studied by Fahey et al. (1955). Two fields, one treated with

DDT spray at 1.5 pounds per acre as an emulsion, and an untreated field were used. Spray was applied June 25 and July 2. Ten-plant samples were taken and chopped with 1-quart samples taken for analysis on July 2, 10

August 10, and September 23. On October 14 stover was sampled for resi­

due. Samples taken July 2, August 10, and September 23 had 116.7, 14.4,

and 11.2 p.p.m. DDT, respectively. Stover samples had 23.3 p.p.m. The

apparent increase in residue on the stover over that on September 23 was

due to the difference in moisture content of the plants. On October 19,

three animals were placed on the DDT-treated fields, and two were placed

on the untreated fields. Biopsy samples from the withers over the poste­

rior portion of the shoulder blade were taken on October 12, November 20,

December 21, February 6, and March 22. All animals were free of DDT at

the beginning of the experiment. After one month animals on the treated

stover showed 1.0 to 2.8 p.p.m. DDT and this increased to 5.0 p.p.m. on

December 21 when the animals were moved to the feed lot. The DDT dimin­

ished rapidly until by March 22 only 0.1 p.p.m. or less was found in the biopsy samples.

Cox et aJ_. (1956b) report that the amount and distribution of DDT residue after second brood treatment was much lower on granular treated plots than sprayed plots. Very little DDT was found on the leaves of plants taken from granular treated plots. In comparison, up to 200 times more residue was found on the leaves of sprayed plants than on those treated with granules. Sprayed plants had about twice as much residue in the leaf axil and stalk area as plants treated with granules.

Fahey et al. (1956) treated corn with granular DDT and DDT emulsion sprays for first- and second-brood corn borer control ttien sampled the corn plants to determine the distribution of the insecticide on the plants.

The emulsion deposited greater residues on the corn leaves than did gran- Il ules, but the granules deposited equal or greater residues in the plant whorls and at the leaf axils. Granular formulations prepared with atta- pulgite or eeli te gave greater deposits than formulations prepared with other carriers. Very similar results were obtained by Cox et al. (1957) in a study on ma lath ion. Granular treated plants had considerably less ma lath ion residue than plants treated with the ma lathion emulsion, but the residue persisted longer on the emulsion treated plants. However, practically all residue was lost in five days. 12

METHODS AMD PROCEDURE

Test Field

All of the experiments were conducted at the European Corn Borer Re­

search Laboratory, Ankeny, Iowa, a cooperative laboratory operated by the

United States Department of Agriculture and the Iowa State College Agri­

cultural Experiment Station.

The corn on which the tests were carried out was grown under the usual agronomic practices such as soil preparation, planting, and cultiva­

tion. No agricultural chemicals, other than fertilizers, were used which might affect the corn borer population.

The hybrid Iowa 4297 was planted in the fields selected for this work.

This variety is susceptible to infestations of the European corn borer.

In addition to planting a susceptible hybrid, the dates of planting were

regulated to insure the heaviest possible natural infestation. Fields used for first brood studies were planted earlier than a majority of the corn in this area. First brood test fields were planted April 27, 25, and

2u in 195o, 1957, and 1353, respectively. Fields used for second brood studies were planted late in the season to attract a heavy second brood

infestation. These planting dates were May 24, 22, and 29 in 195b, 1957, and 1353, respectively.

Insecticides and Formulation

The insecticides included in this study were toxaphene (chlorinated camphene containing 3/ to 3g percent chlorine), heptachlor (3a,4,5,o,7',3, u-octachl oro-2,3,3^Z', /'> 7a-tetrahydro-4,7-methano indene), and endrin (1,2

3,4,10,10-hexachloro-O, 7-epoxy-I,4-, 4a,5,3,7,3,3a-oc tahydro-1,4,5,3-endo-

endo-dimethanonapthc1ene). DDT (1,1,1,trichloro-2,2-bis(p-chloropheny1)

ethane) was included as a comparison in all of the experiments.

All insecticides were applied as granular formulations. .Vnen the

desired formulations were available, the granules were applied at the rat

of 20 pounds per acre. In a few instances, the rates of application of

the granules per acre had to be altered so as to apply the desired amount

of actual toxicant per acre with the formulation available. Table 1 pre­

sents the formulations and rates tested in 19J0, 1957, and 1353 for both

the first and second broods.

DDT was applied at tiie rate of 1 pound of actual toxicant per acre

in all cases except for the first brood test in 1357 when 0.Ù pound of

actual DDT per acre was applied. This was accomplished by applying 20

and 12 pounds, respectively, of a 5 percent formulation.

At least three rates of endrin, toxaphene, and heptachlor were

tested each year. The intermediate dosage was thought to be close to the

rate adequate to give corn borer control. Applications above and below

the intermediate rate were tested in order to determine the relationship

between dosage and mortality. Each succeeding year the range in applica­

tion rates was altered according to the results of the preceding year in an effort to establish the lowest rates with which these toxicants would

give corn borer control equal to the recommended DDT treatment. 14

Table I. Insecticide formulations tested in 1956, 1957, and 1958.

Actua1 Insecticide Year Formulation Insecticide insecticide Pounds/acre Percent Pounds/acre Toxaphene 1956 20 5.0 1.0 20 10.0 2.0 20 15.0 3.0

1957 20 2.5 0.5 20 5.0 1.0 20 7.5 1.5 20 10.0 2.0

1958 20 5.0 1.0 20 7.5 1.5 20 10.0 2.0

Heptachlor 195b 20 2.5 0.5 20 5.0 1.0 20 7.5 1.5

1957 20 1.25 0.25 20 2.5 0.5 20 5.0 1.0

1953 20 2.5 0.5 20 3.75 0.75 20 5.0 1.0

Endrin 1956 20 ' 0.5 0. 1 20 1.0 0.2 20 2.0 0.4

1957 20 0.5 0. 1 20 1.0 0.2 20 2.5 0.5

1958 12.5 1.0 0. 125 12.5 2.0 0.25 10 5.0 0.50

DDT 1956 20 5.0 1.0 (first brood) 1957 12 5.0 0.6 (second brood) 20 5.0 1.0

1958 20 5.0 1.0 15

Experimental Designs

The experimental plots were four rows wide in all experiments

except the second brood test in 1958 when they were three rows wide. In

1956 the plots were 140 feet long but in 1957 and i958 they were short­

ened to 100 feet.

In 1956 a split-split plot experimental design was used. The treat­ ments were applied on two dates on different plots. The date of applica­

tion was assigned to the whole plots, the insecticides on the split plots, and the rates of toxicant were assigned to the split-split plots. With

the exception of the first brood test in 1957 a split plot design was used in both 1957 and 1958. The dates of application were assigned to

the first split and the insecticides and rates were randomly assigned to

the split plot. Four-fold replication was used in all experiments. The design in 1957 for first brood experiments was a randomized block with only one date of treatment.

App1ication Equipment

An experimental f 1 uted-feed granular applicator (Love 1 y £t £]_. 1956) mounted on a high-clearance vehicle was used to apply the formulations.

A rear view of this machine is shown in figure 1. The applicator was equipped with flutes capable of adjustment to deliver a measured amount of granules with each revolution of the flutes. The speed of the revolu­ tion of the flutes was dependent on the speed of vehicle movement. There­ fore the speed at which the vehicle moved in the field was proportional to the amount of material delivered per acre. Extreme differences in speed Figure 1. Experimental fluted-feed granular applicator mounted

on the rear of a high-clearance vehicle. 17 18

affected the amount each flute delivered slightly, so the applicator was

calibrated at the field speed of 4 miles per hour.

The granular applicator was equipped to treat two rows simultan­

eously. Since the experimental plots were three and four rows wide, two

rows were treated and the remaining rows were left as buffer rows to

prevent any insecticide drift into adjoining plots.

Observations on Infestation

The potential infestations and seasonal development of the corn borer in the test fields was determined by making regular observations.

In each field where tests were being conducted, 40 plants were tagged and numbered. Each Monday, Wednesday, and Friday from the beginning to

the end of the ovipos ition period each plant was examined for new egg masses. Each new mass was marked with a felt-tip marking pen and its position recorded. On subsequent observations the mass was checked to determine whether it had hatched or had been destroyed. In the fields where tests on the first brood were conducted, the number of plants which showed evidence of leaf feeding was also recorded. The records on ovi­ pos it ion and leaf feeding were used to determine the date on which the

insecticides should be applied.

Evaluating Borer Reductions

With the exception of the first brood experiment in 1956, to deter­ mine the effectiveness of the various insecticide treatments, ten plants were systematically chosen at random from the two treated rows in each 19

experimental plot. The plants were selected by walking into the plot ap­

proximately seven or eight paces then a plant was taken every tiiree paces

until five plants had been selected from each row. Tagged plants were

used in 195ô to study the results of the treatments. This was done be­

cause of the low infestation that developed on the plots. Ten of these plants were used to evaluate the various treatments.

In the tests on the first brood in 1956, 1957, and 1950 and the

second brood tests in 195^ and 1957, the ten plants from each plot were dissected. The total number of borer cavities and larvae were recorded

for each plant. A different technique was used to determine the effective­ ness of the treatments on the second brood in 1955. The ten plants were selected as before, but instead of dissecting each plant, the plants were split from the top of the stalk to the bottom. The ear shank was also split and examined and the total number of cavities in the plant was re­ corded.

The experiments were sampled when a majority of the larvae were in the fifth instar. The first brood experiments were dissected July o, 25, and 15 in 1956, 1957, and 1953, respectively, whereas the second brood plots were dissected September 14, 13, and !/' in 195o, 1957, and 1953, respectively. Tables 13 through z4 in the appendix present the results of the six experiments.

Insecticide Residues

In order to gain a maximum amount of information on the control with

DDT, heptachlor, and toxaphene the experiments were sampled for residue 20

analysis. The purposes of these analyses were two-fold. One was to gain

information on the location of the toxicants on the plants. The other

was to determine the amount of toxicant on the plants at different inter­

vals after application.

Sampling procedures

First brood I95G. Twenty-four hours after tiie insecticides were

applied on June 20 and 25, ten plants in each plot were sampled. Tiie

plants which were sampled were chosen in tiie same manner as those used to

evaluate the effectiveness of the insecticides for borer control. To

study the distribution of the residue, the plants were divided in the fol­

lowing manner. The tips of tiie whorl leaves were removed followed by re­

moval of the whorl. The leaves of the stall; were then cut about one-half

inch distal to the leaf axil. This was followed by cutting the stalk

about one-half to 1 incii above the ground. Analogous portions of the ten

plants in each plot were then pooled and each sample weighed and frozen.

Figure 2 is a diagrammatic drawing which illustrates how the plant was

d ivided.

On August 10 and October 2, ten plants were again taken at random

from each plot that had been treated on June 25. The ears were removed,

the plants weighed, and run through a silage chopper. A 1-quart aliquot of the chopped material from each group of ten plants was then weighed and

frozen.

Second brood 1956. Twenty-four hours after the plots were treated

for second brood control on July 31 and August 10, ten plants were taken Figure 2. Diagrammatic dissection of a corn plant for

first brood insecticide residue sampling.

at random in the same manner as on the first brood experiment and were

sampled in the following way. The portion of the plant below the ear was

discarded. Five plants were taken and the leaf blade from alternate leaves

beginning with the leaf located at the ear node were removed from about

one-half inch distal to the stall;. The ear was removed and discarded and

the husks from these five plants were pooled for one sample. The alter­ nate leaves from the other five plants were removed beginning with the

leaf blade immediately above the ear. The alternate leaf blades from

tiie ten plants were pooled as the second sample. Alternate internodes from the ten plants were also sampled to make up the third sample. Con­ sequently, the total sample represented tiie parts of tiie stalks above the car of five plants. Figure 3 is a diagrammatic drawing which illus­ trates the sampling procedure.

Additional samples were taken from the plots treated on July 31,

August 21, and October l3- These samples were taken to represent the ensiling and dry ear harvest dates. The same procedure as described for the first brood was followed in taking these samples.

Residue studies 1957 and 1953. The distribution of the residue on the plants was not studied further in 1957 or 1953. The purpose of tiie studies in 1957 and 1953 was to determine the amount of insecticide at intervals after treatment. Samples taken during these years were ob­ tained by selecting ten plants at random from each plot. The ten stalks were chopped and a 1-quart aliquot was taken and frozen.

In 1957, plots treated for first brood control on June 27 were sampled June 23, July 3û, September 3 and 24, and first brood plots Figure ]. Diayramaiatic dissection of o corn plant for

second brood insecticide residue sampling. 25

m 26

treated June 23 in 1933 were sampled June 24, July 23, and September 19.

The second brood experiment was treated August 14 in 1957 and was

sampled for residues August 15, September 1v, and October 19, while the

experiment treated August 13 in 1953 was sampled August 19, September !3,

and October 14.

Comparison of sampling techniques. Since two procedures were em­ ployed to determine the residue one day after treatment, an experiment

'was conducted in 1933 to determine if similar results would be obtained

if both techniques wore used. Granular DDT was applied at the rate of 1 pound of toxicant or 23 pounds of a 3 percent granular formulation per acre for first-brood corn borer control. Twenty-four hours after treat­ ment the procedure used in 1351 end that used in 1937 and 1933 were taken as a comparison.

Chemical Analysis of Residue Samples

After the residue samples were frozen they were sent to Mr. J. t.

Fahey, Pesticide Chemicals Research Laboratory, Vincennes, Indiana where they were analyzed. The DDT samples were analyzed by the Stiff Castillo

Colorimetric method (Fahey and Rusk 1951). Heptachlor residues were de­

termined by the Pol en-S i 1 vernien Col or imetric technique. Three different methods were used to analyze the toxaphene. In 193- the samples taken one day after treatment were determined by the llornstein Colorimetric method while all other toxaphene samples taken in 19.-'o were analyzed by the total chlorine method. In 1957 and l933, the toxaphene samples were analyzed by a colorimetric method developed by the Hercules Powder Company. 27

DISCUSSION AND RESULTS

Effectiveness of Various Insecticides for Corn Borer Control

Toxaphene, endrin, and heptachlor were tested over the three-year

period, 1956 to 1958. One objective of these tests was to establish the

rates of each toxicant in granular formulation adequate to give satis­

factory European corn borer control. DDT at the recommended rate was

included in all of the tests as a comparison.

First brood 1956

All granular formulations were applied at the rate of 20 pounds per

acre in 1956. The insecticides and rates of actual toxicant per acre

tested were as follows: toxaphene 1, 2, and 3 pounds ; heptachlor 0.5,

1.0, and 1.5 pounds ; and endrin 0.1, 0.2, and 0.4 pound. In order to ob­

tain the desired amount of toxicant per acre 5, 10, and 15 percent gran­

ular toxaphene, 2.5, 5.0, and 7.5 percent granular heptachlor, and 0.5,

1.0, and 2.0 percent granular endrin were each applied at the 20-pound

rate. DDT at 1 pound per acre was included as a comparison.

In an effort to apply the insecticides at the time maximum control

could be obtained, the applications were made on separate plots on two

different dates. Observations on the oviposition, the egg hatch, and the percent of plants shov/ing evidence of leaf feeding were used to determine

the time the applications should be made. The first application was made on June 20 when a total of 55 egg masses per 100 plants had been deposited and 38 had hatched. On the same date, 23 percent of the plants showed evidence of leaf damage. On June 25 a second set of plots was treated. 28

No additional new egg masses were observed between the two application

dates. The total number of hatched egg masses was 40 per 100 plants and

33 percent of the plants showed evidence of leaf feeding. Figure 4 shows

the first brood oviposition, hatched masses, and percent leaf feeding in

relation to the two treatment dates.

Due to the low first brood infestation in 1956, 14 plants in each plot treated June 20, which showed evidence of borer infestations, were

tagged before the treatments were made. Ten of these plants were dis­ sected July 5 to determine the effectiveness of the various treatments.

In the plots treated June 25, 20 plants were taken at random and dis­ sected July 6. The number of cavities and larvae were recorded for each plant. Table 19 presents the detailed records of the dissections. The number of cavities, borers, and percent reduction for each treatment are given in table 2.

The results of this experiment were analyzed statistically. An analysis of variance indicated that all of the chemical treatments re­ duced the population significantly below the population in the untreated plots. However, there was no difference between the reduction of larvae and cavities in the DDT treated plots and the other treated plots. Also, there was no difference between the reductions obtained with toxaphene, heptachlor, and endrin. Further analysis of the data indicated that the high and medium rates of application (0.2 and 0.4 pound endrin, 1.0 and

1.5 pounds heptachlor, and 2 and 3 pounds of toxaphene) were significantly more effective than the low rates of application (0.1 pound endrin, 0.5 pound of heptachlor, and 1 pound of toxaphene). Figure 4. Ovi pos it i on, hatched egg masses, and leaf damage in relation to the

dates of application of insecticides for first brood control in 1956. INSECTICIDE APPLIED

i i

0 60 z û LxJ LU 11. 1 40 Lu VaJ < O LU

so y û: NEW MASSES LU HATCHED MASSES û. LEAF DAMAGE i I L 18 20 25 27 JUNE Table 2. Results of applying four granular insecticides for first-brood European corn borer control in 1956.

Cavi ties Larvae Percent Toxicant per 100 Percent per 100 Percent Insect!ci de toxicant per acre plants reduction plants reducti (Pounds) Treated June 20 DDT 5.0 1.0 23 80.4 38 78.9 Heptachlor 2.5 0.5 25 78.3 20 88.7 1 1 5.0 1.0 5 95.7 5 97.2 1 t 7.5 1.5 3 97.8 10 94.4 Toxaphene 5.0 1.0 13 89.1 30 83.1 1 1 10.0 2.0 18 84.8 15 91.5 1 1 15.0 3.0 8 93.5 8 95.8 Endr in 0.5 0. 1 5 95.7 13 93.0 1.0 0.2 5 95.7 13 93-0 " 2.0 0.4 3 97.8 0 100.0 Untreated control 115 178

Treated June 25 DDT 5.0 1.0 6 91.7 6 92.3 Heptachlor 2.5 0.5 13 83.3 9 89.2 1 1 5.0 1.0 0 100.0 3 96.9 I t 7.5 1.5 0 100.0 3 96.9 Toxaphene 5.0 1.0 21 71.7 14 83.1 I I 10.0 2.0 lb 78.3 15 81.5 2 1 15.0 3.0 6 91.7 9 89.2 Endrin 0.5 0.1 13 83.3 10 87.7 1.0 0.2 5 93-3 5 93.8 i ; 2.0 0.4 3 96.7 4 95.4 Untreated control 75 81 32

Table 2 indicates there were more cavities and larvae in the control

plot for the treatment June 20 than the corresponding control plot for the

June 25 treatment. It should be pointed out that the plants dissected in

the plots treated June 20 were all infested when treatments were made.

The plants dissected in the plots treated June 25 were a random selection

of infested and uninfested plants. The percent reduction of cavities and

larvae, based on the number of cavities and larvae in the respective un­

treated control plots, are approximately equal for the two treatment dates

However, there is a trend for slightly better control with DDT when treat­

ments were applied June 25.

Second brood 1956

The same toxicants and rates of application as were tested on the

first brood in 1956 were also tested on the second brood the same year.

Again, the insecticides were applied to separate plots on two different

dates in an effort to apply the materials when maximum control would be obtained. The first treatments were applied on July 31 when there had

been a total of 28 egg masses deposited per 100 plants of which 12 had

hatched. A second set of plots was treated August 7 when the total egg mass count was 51 per 100 plants of which 36 had hatched. The second brood ovipos i tion and hatched masses in relation to the two treatment dates is shown in figure 5.

Ten plants were taken at random from each plot and dissected

September 14 to determine the effectiveness of the treatments. Table 20 presents the detailed results of this experiment. The number of cavities and larvae per 100 plants and the percent reduction are given in table 3» Figure U. Oviposit ion and hatched egg masses in relation to the dates of application

of insecticides for second brood control in IDiK. INSECTICIDE APPLIED 60-

H 50

CL 40 -

LU 30

UJ £ 20

TOTAL NEW MASSES -- TOTAL HATCHED MASSES

20 30 JULY AUGUST Table 3« Results from applying four granular insecticides for second-brood European corn borer control in 1956.

Cavities Larvae Percent Toxicant per 100 Percent per 100 Percent Insect icide toxi cant per acre plants reduction p1ants reduction (Pounds) Treated July 31 DDT 5.0 1.0 63 75.0 65 74.8 Heptachlor 2.5 0.5 65 74.0 78 69.9 5.0 1.0 73 69.0 98 62. 1 7.5 1.5 108 57.0 118 54.4 Toxaphene 5.0 1.0 88 65.0 93 64.1 ii 10.0 2.0 95 62.0 113 56.3 15.0 3.0 100 60.0 100 61.2 Endrin 0.5 0. 1 88 65.0 93 64.1 1 i 1.0 0.2 68 73.0 73 69.9 VJ I. 2.0 0.4 60 76.0 65 74.8 VI Untreated control 250 258

Treated August 7 DDT 5.0 1.0 118 55.7 113 59.4 Heptach1or 2.5 0.5 83 68.9 115 58.5 5.0 1.0 30 88.7 43 84.7 7.5 55 79.2 60 78.4 Toxaphene 5.0 118 58.5 135 51.3 i; 10.0 70 73.6 98 64,9 11 15.0 65 75.5 83 70.3 Endrin 0.5 0. 1 93 65.1 110 60.4 1.0 0.2 123 53.8 110 60.4 2.0 0.4 38 85.8 48 82.9 Untreated control 265 270 36

The results of an analysis of variance were similar to those ob­ tained on the first brood. The borer population in the untreated plots was significantly higher than the population in treated plots. There was no significant difference between the borer reductions obtained with DDT, toxaphene, heptachlor, and endrin. The high and medium rates (0.2 and

0.4 pound of endrin, 1.0 and 1.5 pounds of heptachlor, and 2 and 3 pounds of toxaphene) gave significantly greater borer reductions than the low rates (0.1 pound of endrin, 0.5 pound heptachlor, and 1 pound of toxa­ phene). However, in the over-all analysis, a significant time-by-rate of application showed there was little difference between the effectiveness of the three rates when applied July 31• The difference between the effectiveness of the rates of application was not noticeable on July 31.

As seen in table 3, greater reductions were obtained from treatments applied on August 7 than from treatments applied on July 31. One notable exception was the control obtained with DDT. Application of DDT on July 31 gave 75 percent reduction of the borer population whereas the same treat­ ment on August 7 gave only 55.7 percent reduction.

First brood 1957

In an experiment on the first brood in 1957 granular toxaphene, endrin, and heptachlor were again compared with granular DDT. Some of the rates tested were changed from the 1956 rates. There was only a small dif­ ference between the effectiveness of 2 and 3 pounds of toxaphene per acre in 1956. Based on the 1956 results the adequate rate of toxaphene per acre was considered to be between 1 and 2 pounds. Therefore, in 1957 the rates of toxaphene tested were 0.5, 1.0, 1.5, and 2.0 pounds per acre. Also the rate of application of granular DDT was changed in 1957 to 0.6

pound of actual DDT obtained by applying 12 pounds of a 5 percent granular

formulation, which was the recommendation for that year. Endrin was applied at the rates of 0.1, 0.2, and 0.5 pound per acre. As in 1956, heptachlor was applied at the rates of 0.5, 1.0, and 1.5 pounds per acre.

With the exception of DDT all granular formulations were applied at the

rate of 20 pounds per acre.

Unlike the two previous experiments, the treatments were applied on only one date in the first brood test in 1957. The insecticides were applied on June 27 when approximately 310 egg masses had accumulated of which 170 had hatched. Also on that date 44 percent of the plants showed evidence of leaf feeding. Figure 6 shows the relationship between the oviposit ion, hatched egg masses, leaf feeding, and the application date.

It should be noted that the infestation was much greater than in 1956.

Ten plants from each plot were dissected on July 24 to determine the effectiveness of the treatments. Table 21 presents the actual number of cavities and larvae found in all four replicates. A summary of the ex­ periment and the percent reductions of cavities and borers with the var­ ious treatments is given in table 4.

An analysis of variance on the borer data showed a significant dif­ ference between the treated and untreated plots. Also, endrin, heptachlor, and toxaphene were significantly better than DDT. Granular DDT gave only

42.6 percent borer reduction whereas the least reduction with any of the other treatments was 65.3 percent. It should be emphasized that DDT was applied at 0.6 pound per acre in this experiment. In the two previous Figure 6. Oviposit ion, hatched egg masses, and percent leaf feeding in

relation to the dates of application of insecticides for first

brood control in 1957. INSECTICIDE APPLIED 330 TOTAL NEW MASSES 300 TOTAL HATCHED MASSES if) PERCENT LEAF 1- FEEDING z 270 < -I 240 0- o 2 10 o 180 œ VJ CO UJ cr Û. 150 (Z) LU 120 40h (/) en < 90 S 60 CD 20 w O LU 30

10 12 14 16 17 19 24 26 28 30 2 JUNE JULY Table 4. Results from applying four granular insecticides for first-brood European corn borer control in 1957.

Cavities Larvae Percent Toxi cant per 100 Percent per 100 Percent 1nsecti ci de toxi cant per acre plants reducti on pI ants reductic (Pounds) Treated June 27 DDT 5.0 0. 6 135 57.8 145 42.6

Heptachlor 2.5 0.5 75 76.6 58 77.2 11 5.0 1.0 23 92.8 18 93.1 ii 7.5 1.5 13 95.9 13 95.0

Toxaphene 2.5 0.5 108 66. 3 88 65.3 1 1 5.0 1.0 100 68.8 88 65.3 i! 7.5 1.5 55 82.8 45 82. 2 11 10.0 2.0 63 80.3 65 74.3

Endrin 0.5 0. 1 93 70.9 70 72.3 1 I 1.0 0.2 65 79.7 73 71.3 1 1 2.5 0.5 53 83.4 50 80.2

Untreated control 320 253 40

experiments DDT at 1 pound per acre was equally as effective as the other

materials. Further analysis of the data showed a significant difference

between the rates of application of heptachlor and endrin, but no dif­

ference between the rates of toxaphene. Although the difference in borer

reduction with the four rates of toxaphene was not significant, there was

a definite trend toward better control with the 1.5 and 2.0 pound rates

than with the 0.5 and 1.0 pound rates. There was actually very little

difference between the 1.0 and 1.5 pound rates of heptachlor, but the

big difference was between the 0.5 and 1.0 pound rates. Based on the

number of borers, endrin at 0.1 and 0.2 pound per acre was equally effec­

tive and the 0.5 pound rate was superior. However, there was very little

difference between the effectiveness of the 0.2 and 0.5 pound rates of

endrin when the cavity reductions are considered.

Second brood 1957

The same rates of endrin, heptachlor, and toxaphene as were tested in

the first brood test in 1957 were also tested on the second brood in 1957.

As was pointed out previously in the first brood experiment in 1957, DDT

at 0.6 pound per acre was insufficient to give satisfactory borer control.

Therefore, in the second brood test in 1957 the DDT, as a comparison, was

increased to the 1 pound rate as in 1956.

The insecticides were again applied to separate sets of plots on two dates in an effort to obtain maximum control. One set of plots was treated

August 7. On that date a total of 135 egg masses had been deposited per

100 plants of which 45 had hatched. A second set of plots was treated on 41

August 14 when 265 egg masses had been deposited of which 115 had hatched.

The last new egg masses were found on August 19 at which time a total of

280 egg masses per 100 plants had been deposited. Figure 7 illustrates the oviposi tion and egg hatch in relation to the dates the insecticides were applied. Similar to the first brood infestation, the second brood infesta­ tion in 1957 was much heavier than the corresponding infestation in 1956.

On September 13 ten plants were taken at random from each plot and dissected. The data for this experiment are presented in table 22 and summarized further in table 5 which also gives the percent reductions for the various treatments.

An analysis of variance on the borer data showed there was a signif­ icant difference between the effectiveness of the insecticides. Also there was a significant difference between the borer reductions obtained from the two dates of application. Further analysis gave a significant treatment by date of application interaction. Endrin, heptachlor, and toxaphene gave the greatest larval and cavity reductions when treatments were made August 7- The DOT treatments on August 7 and 14 gave borer re­ ductions of 53-4 and 57.9 percent, respectively.

Endrin at 0.1, 0.2, and 0.5 pound per acre, applied on August 7, gave borer reductions of 66.9, 80.9, and 84.0 percent, respectively. Borer re­ ductions of 56.0, 59.3, and 64.4 percent were obtained with 0.5, 1.0, and

1.5 pounds of heptachlor applied on August 7. Applications of toxaphene of 0.5, 1.0, 1.5, and 2.0 pounds on the same date gave 42.0, 50.4, 57.8, and 52.2 percent reduction, respectively. It is possible that greater re­ ductions would have been obtained if the insecticides had been applied at Figure 7. Oviposit ion and hatched egg masses in relation to the dates of application

of insecticides for second brood control in 1957. INSECTICIDE APPLIED 300 300 i i 275 275 en 250 250 t- z < 22 5 225 _i û. 200 200 o o 175 175 -p- VJ tr 150 150 125 125 en LU 100 100 enCO < 75 TOTAL EGG MASSES 75 o 50 HATCHED 50 o LU EGG MASSES 25 25

• I ' I « I 'i I i I i I 24 26 29 31 I 2 5 7 9 12 14 16 19 21 23 30 JULY AUGUST Table 5. Results from applying four granular insecticides for second-brood European corn borer control in 1957.

Cavi ties Larvae Percent Toxi cant per 100 Percent per 100 Percent Insect ici de toxicant per acre plants reduction plants reduct ion (Pounds) Treated August 7 DDT 5.0 1.0 243 46.9 183 53.4 Heptachlor 2.5 0.5 200 56.3 173 56.0 5.0 1.0 170 62.9 160 59-3 7.5 1.5 148 67.7 140 64.4 Toxaphene 2.5 0.5 278 39.3 228 42.0 5.0 1.0 235 48.7 195 50.4 7.5 1.5 235 48.7 205 47.8 10.0 2.0 215 53.1 108 52.2 Endrin 0.5 0.1 143 68.8 130 66.9 1.0 0.2 90 80. 3 75 80.9 2.5 0.5 68 85.2 63 84.0 Untreated control 458 393

Treated August 14 DDT 5.0 1.0 195 49-7 143 57.9 Heptachlor 2.5 0.5 325 16.2 255 25.0 5.0 1.0 273 29.6 205 39.7 7.5 1.5 230 40.7 208 38.3 Toxaphene 2.5 0.5 263 32.2 210 38.2 I I 5.0 1.0 233 39.9 225 33.8 I I 7.5 1.5 350 9.8 275 19.1 iI 10.0 2.0 210 45.9 178 47.6 Endrin 0.5 0.1 255 34.3 178 47.6 I 1 1.0 0.2 198 49.0 175 48.5 iI 2.5 0.5 290 25.3 288 15.3 Untreated control 388 340 45

an ear]1er date.

First brood 1958

Based on the results obtained in 1956 and 1957, the following ranges

in the rate of application per acre include the necessary amount of toxi­ cant to give borer control comparable to 1 pound of DDT: heptachlor 0.5

to 1.0 pound, toxaphene 1 to 2 pounds, and endrin 0.125 to 0.5 pound.

Therefore, in a test on the first brood infestation in 1958, granular heptachlor at 0.5, 0.75, and 1.0 pound, toxaphene at 1.0, 1.5, and 2.0 pounds, and endrin at 0.125, 0.25, and 0.5 pound of actual toxicant per acre were compared with DDT at 1 pound. To obtain these rates, 2.5, 3.75, and 5.0 percent granular formulations of heptachlor, 5.0, 7-5, and 10.0 percent granular formulations of toxaphene, and 5 percent granular DDT were all applied at the rate of 20 pounds per acre. Granular formulation of endrin containing 1 and 2 percent actual toxicant were applied at

12.5 pounds and a 5 percent granular formulation of endrin was applied at the rate of 10 pounds per acre.

The insecticides were applied to one set of plots on June 23 when a total of 43 egg masses had been found per 100 plants and 30 had hatched.

Thirty-eight percent of the plants showed evidence of leaf feeding on that date. A second set of plots received the same treatments on July 2. On

July 2, a total of 68 egg masses per 100 plants had accumulated of which

48 had hatched and 55 percent of the plants showed evidence of leaf feed­ ing. The oviposit ion, hatched egg masses, and leaf feeding in relation to the treatment dates are shown in figure 8. It should be noticed that the infestation was considerably lighter than in 1957. Figure 8. Ovi pos ition, hatched egg masses, and percent leaf feeding in relation to

the dates of application of insecticides for first brood control in 1953. lOOr INSECTICIDE APPLIED

TOTAL EGG MASSES HATCHED EGG MASSES LEAF DAMAGE 802

-tr w 50 50 w 40h- % 30 < 20 UJ

13 16 18 20 23 25 27 30 2 JUNE JULY 48

The various treatments were evaluated by dissecting ten plants from each plot on July 21. Table 23 presents the data for this experiment and

table 6 shows the number of larvae and cavities per 100 plants and the percent reductions obtained for the various treatments.

It is evident that the greatest cavity and larval reductions re­ sulted from the earlier treatments applied on June 23. An analysis of variance on the borer data failed to show any significant differences be­ tween the toxicants or rates of application. Satisfactory control was ob­ tained with all of the treatments applied on June 23. The borer reduc­ tions range only from 91.7 to 97-2 percent on the plots treated June 23.

It should be pointed out that the percent reductions can be a lit­ tle misleading. The untreated control plots representing the treatment made on July 2 had 28 larvae per 100 plants whereas the control plots for June 23 treatments had 90 larvae. Since the percent reductions are based on the number of borers in the untreated control plots, the plots treated with 0.25 pound endrin on June 23 and July 2 each had eight lar­ vae per 100 plants. However, due to the differences in the number of borers in the untreated plots, the percent reductions were 91.7 and 72.7 for the June 23 and July 2 treatments, respectively.

Second brood 1958

The same experiment as was carried out on the first brood infesta­ tion was also conducted on the second brood infestation in 1958. Similar to all the previously discussed experiments, with the exception of the first brood test in 1957, the insecticides were applied on two dates.

One set of plots was treated on August 7 when there had been a total of Table 6. Results from applying four granular insecticides for first-brood European corn borer control in 1958.

Cavit ies Larvae Percent Toxicant per 100 Percent per 100 Percent Insecticide toxicant per acre plants reduction plants reduction (Pounds) Treated June 23 DDT 5.0 1.0 3 97.6 3 97.2 Heptachl or 2.5 0.5 5 95.2 3 97.2 3.75 0.75 8 92.9 8 91.7 5.0 1.0 5 95.2 5 94.4 Toxaphene 5-0 1.0 8 92.9 5 94.4 Ii 7.5 1.5 8 92.9 5 94.4 10.0 2.0 8 92.9 5 94.4 Endrin 1.0 0.125 8 92.9 8 91.7 11 2.0 0.25 5 95.2 8 91.7 5.0 0.5 10 90.5 3 97.2 Untreated control 10.5 90

Treated July 2 DDT 5.0 1.0 28 54.2 13 54.5 Heptachlor 2.5 0.5 30 50.0 15 45.5 3.75 0.75 25 58.3 13 54.5 5.0 1.0 20 66.7 8 72.7 Toxaphene 5.0 1.0 38 37.5 13 54.5 7.5 1.5 18 70.8 8 72.7 11 10.0 2.0 38 37.5 20 27-3 Endrin 1.0 0.125 50 16.7 28 0 1 1 2.0 0.25 50 16.7 8 72.7 5.0 0.5 33 45.8 8 72.7 Untreated control 60 28 50

ten egg masses deposited per 100 plants of which eight had hatched. A second set of plots was treated August 18 at which time 78 egg masses had accumulated and 43 had hatched. Figure 9 shows the relationship between the oviposit ion, egg hatch, and the treatment dates.

The effectiveness of the various toxicants and rates was evaluated on September 26. In all of the previous experiments ten plants were dis­ sected from each experimental plot. In this experiment a different tech­ nique, which is much simpler and faster, was used to evaluate the treat­ ments. Ten plants were taken at random as before. The ears were removed and the shank was slit lengthwise. Next the plant was slit from the top to the level of the ground. Only the number of cavities for each plant was recorded. The number of cavities for each plot is given in table 24.

The results of the experiment are summarized further in table 7.

An analysis of variance indicated that the number of cavities in the untreated control plots was significantly higher than the cavities in the treated plots. Further analysis of the data failed to show any signifi­ cant difference between the treated plots. However, there was a numerical difference between the cavity reductions obtained on August 7 and August

17 with the DDT and toxaphene treatments. Toxaphene and DDT gave slightly greater cavity reductions when treatments were made August 7.

The percent reduction of the cavities from treatments applied August 7, when the best over-all control was obtained, ranged from 64.5 to 78.5 per­ cent. On that date there was very little evidence that the rates of ap­ plication had any affect on the percent reductions. All of the rates appeared to be approximately equal in effectiveness. Figure 9. Oviposit ion and hatched egg masses in relation to the date of

application for second brood control in 1958. INSECTICIDE APPLIED

TOTAL EGG MASSES HATCHED EGG MASSES

VI M

% 40-

12 13 15 18 20 22 25 27 29 AUGUST 53

Table 7. Results from applying four granular insecticides for second- brood European corn borer control in 1953.

Cavi ties Percent Toxicant per 100 Percent Insecticide toxicant per acre plants reduction (Pounds)

Treated August 7

DDT 5.0 1.0 63 73.1 Heptachlor 2.5 0.5 55 76.3 I1 3.75 0.75 65 72.0 ii 5.0 1.0 50 78.5 Toxaphene 5.0 1.0 73 68.8 i: 7.5 1.5 08 71.0 I! 10.0 2.0 SO 74.2 Endrin 1.0 0.125 55 76.3 1 t 2.0 0.25 83 64.5 11 5.0 0.5 50 78.5 Untreated control 233

Treated August 18

DDT 5.0 1.0 133 48.5 Heptachlor 2.5 0.5 58 77.7 11 3.75 0.75 73 71.8 " 5.0 1.0 38 85.4 Toxaphene 5.0 1.0 130 49.5 I' 7.5 1.5 73 71.8 i I 10.0 2.0 113 56.3 Endrin 1.0 0.125 73 71.8 t 1 2.0 0.25 73 69.9 1J 5.0 0.5 85 67.0 Untreated control 258

Relationship between the Number of Cavities and Larvae

When the experiments on the first brood in 195b, 1957, and 1958 and

the second brood in 1956 and 1957 were dissected, records were taken on

the number of cavities and larvae on a plant basis. Tables 2 through b

show a close relationship between the number of cavities and larvae in 54

these experiments.

Correlation coefficients (r) were calculated to determine the degree

of relationship between the cavities and larvae for each experiment. The

r values obtained for the first broods were as follows: 1956 r = .970

with 20 degrees of freedom, 1957 r = .982 with 10 degrees of freedom, and

in 1958 r = .886 with 20 degrees of freedom. For the second brood the

correlation coefficients were .984 with 20 degrees of freedom and .971

with 22 degrees of freedom for 1956 and 1957, respectively. All of the

correlation coefficients are significant at the 1 percent probability

level. Any values larger than .708, .537, and .515 are significant at the

1 percent level with 10, 20, and 22 degrees of freedom, respectively.

The high correlation between the number of cavities and larvae justi­

fies the procedure used on the second brood experiment in 1958. In this experiment ten plants were split and only the cavities were counted.

Residue Studies

The second objective of this study was to determine if the insecti­ cide residues on corn plants treated for European corn borer control were within the established residue tolerances. At the present time, the res­

idue tolerances as established by the Food and Drug Administration^ for

DDT, heptachlor, and toxaphene are as follows: DDT, 7 p.p.m. in or on

the fat of meat from cattle, sheep, and hogs and no tolerance was request­ ed for DDT residue on corn stover as it does not enter into interstate

1U. S. Code, 1955, Title 21, Part 120. 1958. 55 commerce; toxaphene, 7 p.p.m. on corn stover, and 7 p.p.m. in or on the

fat of meat from cattle, goats, and sheep ; and heptachlor, 0.1 p.p.m. on corn.

Fi rst brood 1956

The first samples to determine the amount of insecticide on corn plants were taken one day after granular formulations of DDT, heptachlor, and toxaphene were applied in tests against a first brood infestation.

Plots treated June 20 and 25 were sampled on June 21 and 26, respectively.

When the samples were taken on both June 21 and 2o they were col­ lected so that the distribution of the insecticide on the plant could be studied. The plants were divided into the following four parts: (1) the whorl leaves, (2) the whorls, (3) stalk leaves, and (4) the stalks and leaf axils. Figure 2 is a diagrammatic illustration of the corn plant which s hows the four plant parts. Ten plants from each plot were chosen at random and the representative parts were pooled to make up the samples.

Each treatment in each of four replicates was sampled.

Table 25 gives the results of each chemical analysis for the samples collected June 21 and 26. The residue in parts per million on the whole plant was calculated by summing the weights and the actual residue content of the four parts. From these totals the average residue per plant was calculated.

On August 10 and October 2 the plots treated June 25 were sampled again. The first date would correspond to the time corn would be chopped for ensilage and the second date the date of the ear corn harvest. On both of these sampling dates, ten plants were taken at random in each plot 56

the ears were husked out, and the stalks were chopped in a small stalk

chopper and quart samples were taken for analysis. The results of the

chemical analyses are given in Table 26.

Table 3 presents a summary of the distribution and the amount of in­

secticide found on the three dates after treatment. The greatest resi­

due deposits were found in the whorl, stalk, and axil samples. The whorl

sample was found to have the heaviest deposit. This distribution of the

insecticide residues on the plant was similar to that reported by Cox et_ aj_. ( 1956a) (193'ob) and Fahey e_t ah (1956).

There was very little difference in the amount of heptachlor residue on plants treated on June 20 with 0.5, 1.0, and 1.5 pounds per acre. How­ ever, the analysis of the samples taken from the heptachlor treatments applied on June 25 and the toxaphene treatments made on both June 20 and

25 showed a greater amount of residue for each increased level of applica­ tion. Residues on plants one day after treatment with I pound of DDT were quite similar in magnitude to residues on plants treated with 1 pound of heptachlor or toxaphene.

When sampled at normal ensiling maturity (August 10), the heptachlor treated plots which had from 5.1 to 24.4 p.p.m. on June 25 all had less than 0.1 p.p.m. residue. There was only 0./ p.p.m. DDT on this date after an initial residue of 6.9 p.p.m., whereas 2.35 p.p.m. toxaphene residue was found on the plants which had 37-3 p.p.m. on June 26.

Residue samples taken at harvest time (October 2) showed that the DDT and heptachlor treated plots had essentially the same residue as the sam­ ples taken on August 10. The toxaphene residue was approximately twice as Table 8. Insecticide residues following insecticide applications for first-brood European corn borer control, 195b.

Parts per million Rate Whorl Stalk Stalk and Tota 1 Harvest Insecticide per acre 1 eaves Whorl 1 eaves axi 1 plant Ensi1aqe stover (Pounds)

Treated June 20 Sampled June 21

DDT 1.0 1.0 27.0 0.7 8.2 8.7

Heptachlor 0.5 0.8 42.0 0.2 6.3 9.9 ;i 1.0 1.6 35.4 0.3 9.6 10.5 11 1.5 1.5 42.3 2.4 8.2 13.3

Toxaphene 1.0 8.4 39. u 2.7 9.0 12.4 1 I 2.0 14.5 65.8 3.5 31.3 31.2 iI 3-0 14.0 137.0 4. 7 46.0 47.8 Sampled Samp 1ed Treated June 25 Sampled June 2b August 10 October 2

DDT 1.0 0.2 33.1 0.5 7.4 6.9 0. 7 0.7

Heptachlor 0.5 0.1 19.9 0.1 1.3 5.1 0. 1 0. 1 I i 1.0 0.1 49.4 0.1 1.1 5.8 0. 1 0. 1 t 1 1.5 0.1 92.4 0. 1 19.1 24.4 0. 1 0. 1

Toxaphene 1.0 7.0 44.0 3.8 5.6 10.5 0. 54 1.13 I t 2.0 8.6 164.3 7.1 13.9 35.5 1. 24 2.78 i « 3.0 18.8 202.5 17.9 7.2 37.3 2. 33 4.54 high on October 2 as on the ensiling date (August 10). This apparent in­

crease in the toxaphene residue might be explained by the difference in

the moisture content of the plant. On August 10 the corn plants still

contained a relatively high amount of moisture, whereas the corn plants

were considerably drier on October 2 when the last samples were taken.

This would, of course, result in a higher percentage of toxaphene by weight. Also, at ensiling time (August 10) the leaves were still on the corn plants and added to the sample weight, but on October 2 many of the

leaves which initially had lower toxaphene residue were broken off by

the wind. This resulted in the sample arising largely from the stalks and axils, which had initial high residue, as the main portions of the sample. This same explanation is true for samples taken from the DDT and heptachlor treated plots. On a dry weight basis there would be less DDT and heptachlor on October 2 than August 10.

Second brood 1956

The distribution of the residue one day after treatment and the amount of insecticide remaining at ensiling and harvest time were also studied for second brood. Plots treated July 31 and August 7 were sampled on August 1 and 3, respectively. In addition to the sample taken on

August 1, the plots treated July 31 were sampled again on August 21 and

October 13.

In the residue samples taken on August 1 and 8, the portion of the plants above the ear was divided into three parts: (1) the leaves, (2) the husks, and (3) the stalk and axils. The diagrammatic drawing of the corn plant in figure 3 illustrates how the plants were divided. Table 27 presents the results of the individual analyses. In this sampling the portion of the plants below the ear was not included. It is likely that the average residues for the entire plant would be different from the av­ erage residue for that portion of the plant above the ear. Since the granules are released from the applicator above the plant, the upper por­ tion of the plant would probably have the greatest residue deposit.

The sampling procedure followed on August 21 and October 13 was the same as that used on August 10 and October 2 in the first brood residue study. The results of the chemical analyses for the samples taken at en­ siling and harvest time are given in table 28.

As table 9 shows, the largest deposit of heptachlor residue one day after application on July 31 was on the stalk and axil areas whereas the greatest toxaphene residue was on the husks. Although toxaphene was ap­ plied at twice the rate of heptachlor, the amount of toxicant on the stall and axil area of plants treated with the two insecticides was approxi­ mately equal. The greatest residue deposit on the plants treated August

7 was again found on the stalk and axil area. Plants treated with tox­ aphene on the same date had approximately the same amount of toxicant on the husks and on the stalks and axils. The toxaphene residue on the leaves was only slightly less than that found on the husks, stalks, and axi1s.

When plants treated with equal rates of DDT, heptachlor, and toxa­ phene were sampled, the DDT and heptachlor residue above the ear was ap­ proximately equal. However, the toxaphene residue on the plant above the ear was 4 to 10 times as great as those found for heptachlor and DDT. Table 9. insecticide residues following insecticide applications for second-brood European corn borer control, 1956.

Parts per million Rate Stalk and Plant above Harvest Insecticide per acre Leaves Husks axil the ear Ens i1 age stover (Pounds) Sampled Sampled Treated July 31 Sampled August 1 August 21 October 13

DDT 1.0 0.7 1.0 1.9 1.4 0.9 0.9

Heptachlor 0.5 0.2 0. 1 1.3 0. 6 0.1 0.05 I 1 1.0 0.5 0.5 3.8 2.2 0.7 0. 1 i 1 1.5 0.7 0.2 4.4 2.6 0.9 0.05

Toxaphene 1.0 15.3 9.2 0.3 5.9 2.4 1.2 II 2.0 9.8 10.2 4.8 7.7 4.4 4.9 I\ 3.0 7.0 11.9 3.9 6.5 4.7 3.9

Treated August 7 Sampled August 8

DDT 1.0 0.5 0.3 0.9 0.6

Heptachlor 0.5 0. 1 0. 1 0.4 0. 1 I I 1.0 0. 1 0.4 0.9 0.6 i I 1.5 0. 1 0.5 1.5 0.9

Toxaphene 1.0 4.1 9.9 5.8 6. 6 1 I 2.0 3.0 5.0 7.9 6. 7 i; 3.0 4.5 7.2 6.9 6.4 61

It should be noted that the residue on the plants in all of the

treatments was relatively low as compared to the amount of toxicant on

the plants after first brood applications (table 8). Light rains im­

mediately after the materials were applied on both July 31 and August 7 may have reduced the residue deposits.

As shown in table 3, there was very little difference in the amount

of insecticide on the plants due to the different rates of application.

This was in contrast to the results obtained in the first brood study.

There was a noticeable loss in heptachlor residue during the three

weeks that elapsed after the material was applied, as shown by the samples

taken on August 21. Although there was also loss of DDT and toxaphene,

the magnitude of the loss was not as large as with heptachlor (table 9)•

Samples for residue analysis taken from the same plots again on

October 13 indicated the DDT and toxaphene residues were approximately equal to those on the ensilage samples of August 21. On August 21 the heptachlor residues were 0.1, 0.7, and 0.9 p.p.m. for the 0.5, 1.0, and

1.5 pound per acre rates, respectively, whereas the residues for these rates were<0.05, 0.1, and<0.05 p.p.m. on October 13.

Fi rst brood 1957

The residue study conducted in 1957 was not as extensive as the study in 195&. The distribution of the residue on the plant was not studied any further. Also, only one rate of application of each insecticide was sampled. As was discussed in a previous section, DDT was applied at the rate of 0.6 pound per acre instead of 1 pound as in 1956. Results of tests in 195b indicated that 1 pound of heptachlor and 2 pounds of toxa- 62

phene per acre were adequate to give satisfactory corn borer control.

Therefore, plots receiving these treatments were sampled for residue in

1957.

The first brood treatments were applied on June 27 in 1957. Residue

samples were taken on June 23, July 30, September 3, and September 24.

The sampling procedure on all four dates was similar. Ten plants were

chosen at random from the treatment plots, chopped and quart samples taken

for analysis. For the samples taken September 3 and 24, the ears were re­

moved before the plants were chopped.

Table 29 presents the results of the individual analyses and table 10

summarizes the residues remaining at intervals following treatment. The

DDT residues found on June 28, July 30, September 3, and September 24 were

1.1, 1.6, 1.0, and 0.4 p.p.m., respectively.

All samples taken July 28 and thereafter for heptachlor residue deter­ mination showed only a trace of heptachlor or less than 0.1 p.p.m. Appar­

ently there was a rapid loss of heptachlor during the first 30 days fol­

lowing treatment.

Toxaphene also disappeared rapidly during the first 30 days after

treatment. Samples taken June 28 showed 14.6 p.p.m. and by July 30 the

toxaphene residue had declined to 1.3 p.p.m. Samples taken September 3 and 24 had 2.4 and 2.1 p.p.m., respectively. The apparent increase in

toxaphene residue from July 30 to September 3 can be attributed to the difference in the moisture content of the corn plants. As shown in table

10, the toxaphene residue, based on the dry weight, is approximately equal on the samples taken July 30 and September 3- It should be pointed out 63

Table 10. Insecticide residues following insecticide applications for first-brood European corn borer control, 1957.

Parts per million Residue Residue Rate Sampling on fresh on dry Insect!c ide per acre date Moi s ture weiqht weiqht (Rounds) (Percent)

DDT 0.6 6/23 56.5 1.1 8.2 7/30 76.4 1.6 6.8 9/3 44.9 1.0 1.8 9/24 47.9 3.4 0.8

Heptachlor 1.0 6/28 86.5 5.0 37.5 7/30 76.4 0. 1 - 9/3 44.9 0. 1 - 9/24 47.9 0. 1 -

Toxaphene 2.0 6/28 86.5 14.6 108.1 7/30 76.4 1.3 5- 5 9/3 44.9 2.4 5-3 9/24 47.9 2. 1 4.0

that part of the difference in insecticide residue found on June 28 and

July 30 is due to the increased size of the plant July 30. The insecti­ cide residues in p.p.m. that remained on the plant were diluted by the additional plant tissue.

Second brood 1957

Plots treated on August 14 for second brood control were sampled

August 15, September 16, and October 19. As in the preceding experiment, ten plants were taken at random from the treated plots on each sampling date. The ears were removed from the plants sampled on September 16 and

October 19. Each sample of ten plants was then chopped and a quart taken for residue analysis. 64

Table 30 in the appendix presents the results of the individual anal

yses. The residue remaining after each treatment and sampling date is

shown in table 11. Application of 1 pound of DDT in a granular formula­

tion resulted in residues of 9.0, 5- ô, and 5-0 p.p.m., for samples taken

August 15, September lb, and October 19, respectively.

Corn samples taken August 15 for residue determination from plots

treated with 1 pound of heptachlor had 1.4 p.p.m. residue. Samples

taken on September 16 and October 19 both showed less than 0.1 p.p.m. heptachlor. Following application of 2 pounds of toxaphene, 11.6, 3.5, and 2.9 p.p.m. residue remained on August 15, September 16, and October

19, respectively.

Table 11. Insecticide residues following insecticide applications for second-brood European corn borer control, 1957.

Parts per million Residue Residue Rate Sampling on fresh on dry 1nsect ici de per acre date Moisture weight weight (Pounds) (Percent)

DDT 1.0 0/15 79.0 9.0 42.9 9/16 77.6 5. 6 25-0 10/19 39.4 5.3 3.3

Heptachlor 1.0 0/15 79.0 1.4 6.7

9/16 77.6 0.01 - 10/19 39.4 0.01 -

Toxaphene 2.0 8/15 79.0 11.6 55.2 9/16 77.6 3.5 15.0 10/19 39.4 2.9 4.8 65

Fi rst brood 1958

The objective of the residue studies in 1958 was the same as in

1957) which was to determine the amount of each insecticide remaining on

the corn at various intervals after treatment. However, the rates of ap­

plication that were sampled were slightly different in 1958 from the prev­

ious year. Based on the borer reductions obtained in 1956 and 1957, it

was concluded that 0.75 pound of heptachlor and 1.5 pounds of toxaphene

per acre would be adequate to give satisfactory control. Therefore, the

residue deposits found following these application rates were determined.

Residues remaining after the application of 1 pound of DDT in a granular

formulation were determined again in 1958.

The granular insecticides were applied on June 23 to study the con­

trol of the first brood. Treated plots were sampled June 24, July 23, and September 19. Samples for residue determination were obtained by using the same procedure followed in 1957. Table 31 of the appendix pre­ sents the results of the individual analyses and table 12 summarizes the residue data for the three dates following application of granular formu­ lations.

Following application of 1 pound of DDT, residues of 36.2, 0.9, and

0.4 p.p.m. were found on samples taken June 24, July 23, and September 19, respectively. The greatest decrease in the DDT residue occurred during the first 30 days following application.

One day after application of 0.75 pound of heptachlor per acre, there was a residue of 3.8 p.p.m. on the corn. Samples collected July 23 and

September 19 showed less than 0.05 p.p.m. of heptachlor. Samples for tox- 66

Table 12. Insecticide res idues following insecticide applications for first-brood European corn borer control, 1953.

Parts per million Res idue Res idue Rate Sampli ng on fresh on dry 1nsect icide per acre date Mo is ture wei cjht weight (Pounds) (Percent)

DDT 1.0 6/24 88.3 36.2 309.4 7/23 83.8 0.9 5.6 9/19 60.7 0.4 1.0

Heptachl or 0.75 6/24 88.3 3.3 32.4 i/13 83.8 0.05 - 9/19 60.7 0.05 -

Toxaphene 1.5 6/24 88.3 6. 6 56.4 7/23 83.8 0.7 4.3 9/19 60.7 0.9 2.3

phene determination resulted in 6.6, 0.7, and 0.9 p.p.m. residue on

June 26, July 23, and September 19, respectively. The decrease of DDT, heptachlor, and toxaphene residues the first 30 days after application results from the dilution of the residues by plant growth as well as the actual loss of insecticide.

Second brood 1953

Plots treated August 13 for second-brood borer control were sampled

August 19, September 16, and October 19. The sampling procedure was the same as that followed in 1957. Table 32 presents the results of the in­ dividual analyses and table 13 gives the average residue deposits for each treatment and sampling date.

One pound of DDT per acre as a granular formulation left residue de­ posits of 0.8, 1.5, and 1.6 p.p.m. when samples were taken August 19, 67

Table 13. Insecticide residues following insecticide applications for second-brood European corn borer control, 1958.

Parts per million Residue Residue Rate Sampling on fresh on dry 1nsecti ci de per acre date Moi s ture weight weight (Pounds) (Percent)

DDT 1.0 0/19 03.7 0.3 4.9 9/I& 33.1 1.5 8.9 10/14 77.1 1.6 7.0

Heptachlor 0.75 3/19 33.7 0.64 3-9 9/16 33.1 0.14 0.8 10/14 77.1 0.09 0.4

Toxaphene 1.5 3/19 33.7 2.9 17.3 9/16 03.1 1.5 8.9 10/14 77-1 1.6 7.0

September 16, and October 14. The residue deposits following the appli­ cation of 0.75 pound per acre were 0.6, 0.1, and less than 0.1 p.p.m. on the three dates of sampling. Samples collected to determine the toxa­ phene residue on August 19, September 16, and October 14 showed residue deposits of 2.9, 1.5, and 1.6 p.p.m., respectively.

Comparison of residue deposits for 1956, 1957, and 1958

Before the residues deposits found in 1956, 1957, and 1958 could be compared it was necessary to make some adjustments to compensate for the differences in the rates of application of ODT, heptachlor, and toxaphene.

DDT was applied at the rate of 0.6 pound per acre in the first brood studies in 1957, but was applied at 1 pound per acre in all the other studies. In order to make a uniform comparison possible it was decided to calculate the residue which would have been present if 1 pound of DDT had been applied in the first brood test in 1957. For example, one day after 0.6 pound of DDT was applied for first brood control the residue deposit was 1.1 p.p.m. Theoretically, if 1 pound had been applied ap­ proximately 1.8 p.p.m. should have been found. This assumes that the

residue deposits would be directly proportional to the rate of applica­

tion. Also it must be assumed that following application of an insecti­ cide at two rates the residue deposits would decline at an equal rate.

Corn treated with 2.0 pounds of toxaphene and 1.0 pound of heptachlor was sampled for residue determination in 195b and 1957. In 1958 corn treated with 1.5 pound of toxaphene and 0.75 pound of heptachlor was sampled.

Based on the borer reductions obtained, toxaphene at 1.5 pound and hepta­ chlor at 0.75 pound per acre are adequate for corn borer control. There­ fore, the residue deposits found in 195b and 1957 have been adjusted to the lower rates so the residue data for 1956, 1957, and 1953 may be com­ pared. Table 14 presents the adjusted DDT, heptachlor, and toxaphene residue deposits found one day after application of 1 pound of DDT, 0.75 pound of heptachlor, and 1.5 pounds of toxaphene and the residues at the time the corn was harvested for both the first and second broods.

As shown in table 14, there was a wide variation in the DDT residues recovered one day after application for first brood control. The residue deposits of DDT were 6.9, 1.3, and 36.2 p.p.m. in 1956, 1957, and 1953, respectively. At first it was thought that the different sampling pro­ cedures used in 1956 and 1957 might be the reason for the difference be­ tween the results obtained those years. However, the residue remaining in 1953 did not agree with that found in l957 when the same procedure was Table 14. Comparison of insecticide residues following application of granular insecticides in 1956, 1957, and 1958.

Parts per million First brood Second brood Rate One day Harvest One day Harvest per Fresh Dry Fresh Dry- Fresh Dry Fresh Dry Insecticide acre Year weight weight weight weight we ight weight weight weiaht * (Pounds)

DDT 1.0 1956 6.9 - 0.7 - 1.4 - 0.9 - 1957 1.8 13.7 0.7 1.3 9.0 42.9 5.0 8. 3 1958 36.2 309.4 0.4 1.0 0.8 4.9 1.6 7.0

Heptachlor 0.75 1956 4.5 - 0. 1 1.7 - 0. 1 - 1957 3.8 23. 1 0. 1 - 1. 1 5.0 0.01 - 1950 3.3 32.4 0.05 - 0.64 3.9 0.09 0.4

Toxaphene 1.5 1956 26.6 - 2. 1 - 5. 0 - 3.7 - 1957 11.0 31.1 1.6 3.0 8.7 41.4 2.2 4.0 1958 6. 6 56.4 0.9 2.3 2.9 17.0 1.6 7.0 followed. An experiment to compare the two sampling procedures was con­

ducted in 1958 and is discussed in a later section.

Although there was a large variation in the DDT residues one day

after application, the residue deposits of DDT at ear harvest were quite

uniform for the three years. The DDT residue at the time the corn was

harvested was 0.7, 0.7, and 0.4 p.p.m. in 1953, 1957, and 1958, respec­

tively.

Table 14 also shows a variation in the amount of DDT found one day

after application for second brood control. The residue deposits of DDT

were 1.4, 9.0, and 0.8 p.p.m. in 1956, 1957, and 195o, respectively. It

is important to note that in 1956 the samples collected one day after

treatment were taken by dissecting the corn plants and only the portion

of the plant above the ear was included in the samples (figure 3). In

1957 and 1958 the entire plant was chopped and a quart of the chopped

material was taken for residue analysis. Since the entire plant was in­

cluded in the samples for residue determination in 1957 and 1958 but

only the portion above the ear was included in 1956, it is not possible

to make an accurate comparison between the residue deposits one day after

application in 1956 and the corresponding deposits found in 1957 and 1958.

At the time of corn harvest, there was also a considerable variation

in the DDT residue after treatment for second brood control. The residue

deposits ranged from 0.9 p.p.m. in 1956 to 5-0 p.p.m. in 1957. However,

if the residues found when the corn was harvested in 1957 and 1958 (5.0

and 1.6 p.p.m.) are calculated on the dry weight of the plants they are

3.3 and 7.0 p.p.m., respectively. The moisture content of the plants at 71

harvest was not determined in 1956.

The heptachlor deposits one day after application of granular hepta­ chlor at 0.75 pound per acre for first brood control was much more uni­ form than the corresponding DDT deposits in 1956, 1957, and 1958. In both 1957 and 1958 the heptachlor deposit at this time was 3-8 p.p.m. and in 195o, 4.5 p.p.m. remained. The slightly higher residue deposit found in 1956 may be due to the modified sampling technique followed that year. When the corn was harvested, less than 0.1 p.p.m. heptachlor was found on the stover for all three years.

The deposits found one day after application of granular heptachlor for second brood control were more uniform than the corresponding DDT deposits. In 1956, 1957, and 1958 the heptachlor deposits were 1.7, 1.1, and 0.6 p.p.m., respectively. As was pointed out previously, a modified sampling technique was used in 1956 which may account for the slightly higher residue deposit in that year. However, all three years after treatment for first brood control less than 0.1 p.p.m. of heptachlor was found at the time the corn was harvested.

The toxaphene residues varied from year to year, but the differences were not as pronounced as they were for DDT. The toxaphene residues one day after applications for first brood control in 1956, 1957, and 1958 were 2b.6, 11.0, and 6.6 p.p.m., respectively. Again, the difference be­ tween the residue deposit found in 1956 and those in 1957 and 1958 may be due to the sampling techniques followed. At the time of corn harvest, the toxaphene residue that remained after first brood treatment was 2.1,

1.6, and 0.9 p.p.m. in 1956, 1957, and 1958, respectively. 72

The toxaphene residues one day after application of 1.5 pounds of

toxaphene as a granular formulation for second brood control were 5.8,

8.7, and 2.9 p.p.m., respectively. Once again, it should be mentioned

that the 1957 and 1958 data cannot be compared with the 1956 results as

two different sampling techniques were used. At harvest the toxaphene

residue had declined to 3-7, 2.2, and 1.6 p.p.m. in 1956, 1957, and 1958

respect i vely.

As shown in table 14, the residue on the corn plants one day after application of granular insecticides was higher following first brood

treatments than that found following second brood treatments with all

three insecticides each year except in 1957- In 1957 the DDT residue after second brood applications was greater than the DDT deposits after first brood applications.

Although the initial residues were higher after first brood treat­ ments, as a rule, the residue when the corn was harvested was higher on corn treated for second brood control. However, the heptachlor residue deposit at harvest time was less than 0.1 p.p.m. following treatment for either first or second brood control.

Heptachlor and heptachlor-epoxide

According to Gannon and Decker (1958), heptachlor is converted to its epoxide on plants. They reported that the epoxide remains on plants longer than the parent material and also has a higher insect and mammalian toxicity. Since the epoxide is more toxic than the parent material it was necessary to determine the amount of epoxide as well as the parent mater­ ial on corn treated for corn borer control. 73

In 1957, corn treated July II with 20 pounds of 5 percent granular

heptachlor was sampled July 12, 15, 19, 29, and August 12 or 1, 4, 8, 18,

and 32 days, respectively, after treatment. The samples were analyzed

for both heptachlor and heptachlor-epoxide. Table 15 presents the results

of the analyses.

Table 15. Heptachlor and heptachlor-epoxide residues following applica­ tion of granular heptachlor for first-brood corn borer con­ trol, 1957.

Parts per million Days Heptachlor HeptachI or -epoxide Samp!ing after Fresh Dry Fresh Dry date treatment Ho is ture weight weight weight weight (Percent)

July 12 1 85.4 1.14 7.80 0.04 0.27

15 4 88.1 0.55 4.62 0. 15 1.26

19 8 33. 1 0.01 - 0.07 0.41

29 18 79.3 0.01 - 0.06 0.29

Aug. 12 32 78.5 0.01 - 0.03 0.14

Heptachlor-epoxide was found on corn plants one day after treatment but the concentration was greatest in the samples taken four days after

treatment. Eight days after treatment the heptachlor residue had almost completely disappeared, but heptachlor-epoxide residues were found at low

levels 32 days after treatment.

In 1953, heptachlor at the rate of 20 pounds of a 3.75 pound granular formulation or 0.75 pound actual heptachlor per acre was applied June 23 in a first brood test. Samples were taken June 24, July 23, and September 74

19, or 1, 30» and 83 days after treatment. The samples were analyzed for both heptachlor and heptachlor-epoxi de. Table 16 presents the results of

the analyses.

The samples taken one day after treatment showed 3-8 p.p.m. hepta­ chl or residue which after 30 days declined to less than 0.05 p.p.m. of heptachlor. On the contrary, the heptachlor-epoxide residue was less than 0.1 p.p.m. one day after treatment, while after 30 days it increased to 0. 1 p.p.m.

Table lu. Heptachlor and heptachlor-epoxi de residues following applica­ tion of granular heptachlor for first-brood corn borer control, 1950.

Parts per mi 11 ion Days Heptachlor Heptachlor-epoxide Sampling after Fresh Dry Fresh Dry date treatment Moisture weight weight weight we ight (Percent)

June 24 1 33.3 3.30 32.43 0.1 -

July 23 30 33« 0 0.05 - 0.10 0.62

Sept. 19 38 60.7 0.05 - 0.04 0. 10

Granular heptachlor at 0.75 pound of actual heptachlor was also ap­ plied August 18 in an experiment to control the second brood. Samples to determine residues were taken August 19, September 16, and October 14 and analyzed for heptachlor and heptachlor-epoxi de. The results of these analyses are presented in table 17.

During the period of study there was a progressive increase in the heptachlor-epoxide residue on the corn plants while at the same time the IS

Table 17. Heptachlor and heptachlor-epoxi de residues following applica­ tion of granular heptachlor for second brood control, 1958.

Parts per mill!on Days Heptachlor Heptachlor-epoxi de Sampli ng after Fresh Dry Fresh Dry date treatment Moisture weight weight weight weight (Percent)

Aug. 19 1 33.7 0.64 3-93 0.06 0.37

Sept. lb 29 33.1 0.14 0.83 0.13 0.77

Oct. 14 67 77.1 0.09 o.39 0.23 l.oo

heptachlor residue was decreasing. On October 14, there was 0.23 p.p.m. of hep tach1or-epoxi de residue which is two and one-half times greater

than the heptachlor residue.

Comparison of sampling procedures

The procedure used to gather and process the residue samples one day after the first brood treatments in 1956 was different from the procedure used in 1957 and 1958. Because the residues found varied widely an ex­ periment was conducted in 1958 to compare the procedures. Granular DDT at 1 pound of toxicant per acre was applied to corn in the whorl stage.

One day after the treatment was made the corn was sampled by the two pro­ cedures.

Four groups of ten plants were chosen at random from the treated plot. Each group of plants was sampled by the procedure used in 1956

(figure 2). The results of the analyses of the individual samples are given in table 1o. The residue on the entire plant is calculated by mul­ tiplying the p.p.m. DDT on the plant parts by the percent of the total Table 13. DDT residues following application of granular DDT for first-brood European corn borer control, 1952.

Percent Percent Percent Percent Average of total of total of total of total residue Replicate Residue weight Residue weight Residue weight Residue weight on plant (p.p.m.) (p.p.m.)(p.p.m.)(p.p.m.) (p.p.m.)

1 65.3 14.9 6.4 14.6 2.9 9.8 3.5 60.7 13.1

2 102.1 16.4 6.1 17. 1 2.1 9.3 1.6 57.2 18.9

3 37.4 13.6 3.9 13.3 1.8 10.3 3-2 62.0 7.8

4 102.4 15.7 6.0 14.8 3.4 10.3 1.6 50.7 18.3

Average 76.8 15.2 5.6 15-0 2.6 10.1 2.5 59.3 14.5 77 weight attributed to that part of the plant. The sum of the total resi­ due fraction of all plant parts is the total plant residue. Using this technique the residue on the plants ranged from 7-3 p.p.m. to 13.9 p.p.m. for the four groups of samples with an average of 14.5 p.p.m.

The sampling procedure used in 1957 and 1958 was also used. Another four groups of ten plants were chosen at random. Each group was chopped and a 1-quart aliquot was taken from each for analysis. The four samples showed 6.1, 8.4, 10.2, and 13-9 p.p.m. DDT residue with an average of 9.7 p.p.m.

The total plant residue calculated from the analyses of plant parts exceeds the average residue obtained by analyses of aliquots of whole plant samples. It is possible that the loss of residue from the plant surface in the process of chopping may account for this difference. How­ ever, when plant parts are taken some residue is also lost, so the differ­ ence may also be due to normal variation in application and sampling. It should be pointed out that the difference between the residue found by the two procedures is not large enough to account for the large difference in residues found one day after treatment in 195b, 1957, and 1958. 73

SUMMARY AND CONCLUSIONS. .

Experiments were conducted at Ankeny, Iowa from 1956 to 1953 to de­

termine the rates of endrin, heptachlor, and toxaphene in granular formu­

lations adequate to give effective corn borer control. Granular DDT at

the recommended rate was used as a standard for comparison in all exper­

iments.

Samples of corn plants treated with granular DDT, heptachlor, or toxaphene for borer control were taken at intervals from one day after application until harvest time. These samples were analyzed to determine the insecticide residues remaining. In 1956 corn treated for first brood control and also corn treated for second brood control was sampled to determine the distribution of the insecticide on the plants.

In addition to analyses for heptachlor residue, samples taken in

1957 and 1958 were also analyzed for heptachlor-epoxide.

Two procedures were used to sample the corn one day after treatment.

Corn was treated with granular DDT and sampled by both procedures in 1953 to determine if similar results would be obtained.

Based on the results obtained in these tests, the following conclu­ sions may be drawn:

(1) Granular endrin, heptachlor, and toxaphene at 0.2, 0.75, and

1.5 pounds of actual toxicant per acre, respectively, are equally as ef­ fective for first and second brood control as granular DDT at 1 pound.

(2) Granular DDT at 0.6 pound of actual toxicant per acre is in­ sufficient to give satisfactory corn borer control.

(3) Expressed as percent reduction of cavities or borers, endrin, heptachlor, toxaphene, and DDT all give better control of the first brood than second brood.

(4) There is a high correlation between the number of cavities and larvae when the plots are dissected to evaluate first- or second-brood corn borer control experiments.

(5) One day after granular insecticides are applied for first-brood borer control, the greatest amount of residue is found on the spirally rolled leaves of the ;:whorl.11 The least residue is found on tips of the leaves.

(6) The initial residue deposits on the plants are greater after granules are applied for first brood control than after second brood treat­ ments.

(7) At the time the ears are harvested, more residue is found on corn treated for second brood control than on corn treated for first brood control.

(3) Residue deposits after application of 1 pound of DDT and 1.5 pounds of toxaphene for first-brood borer control ranged from 0.4 to 0.7 and 0.9 to 2.1 p.p.m., respectively. The residue deposits following ap­ plication of the same rates of DDT and toxaphene for second brood control ranged from 0.9 to 5.0 and 1.6 to 3-7 p.p.m., respectively. Less than 0.1 p.p.m. heptachlor residue was found following application of 0.75 pound of heptachlor for first or second brood control. All of these residue de­ posits are within the established tolerances.

(9) Heptachlor is converted to its epoxide on corn plants. These deposits ranged from 0.03 to 0.04 p.p.m. at ear harvest after application 30

of granular heptachlor for first-brood corn borer control, while 0.23 p.p.m. was found at ear harvest after applications for second brood con­ trol. LITERATURE CITED

Apple, J. V/. and G. C. Decker 1949 Insecticide] dust formulations for corn borer control. Jour. Econ. Ent. 42:38-92. Baker, W. A. and D. 0. Questel 1939 Investigations of insecticides for control of the European corn borer at Toledo, Ohio, 1937-38. Jour. Econ. Ent. 32: 526-530. Batchelder, C. H. and D. D. Questel 1931 Insecticidal control of the European corn borer: The prob­ lems involved and some experimental results. Jour. Econ. Ent. 24:1152-1167. and 1945 Experiments with DDT for the control of the European corn borer infesting sweet corn at Toledo, Ohio, in 1944. U. S. Dept. Agr. Bur. Ent. and Pl. Quar. £-659. Beard, R. L. and Nee 1v Turner 1942 Investigations on the control of the European corn borer. Conn. (Mew Haven) Agr. Exp. 5ta. Bui. 462:551-591. Bradley, V.'. G. 1952 The European corn borer. U. S. Dept. Agr. Yearbook 1952: D14-b21. Cox, H. C., T. A. Brindley, W. G. Lovely, and J. E. Fancy 1956a Granulated insecticides for European corn borer control. Jour. Econ. Ent. 49:113-119• , J. E. Fahey, and T. A. Brindley 1957 European corn borer control in relation to ma lathi on resi­ dues. Jour. Econ. Ent. 50:52-55. , W. G. Lovely, and T. A. Brindley 1956b Control of the European corn borer with granulated insecti­ cides. Jour. Econ. Ent. 49:834-038. Cutkomp, L. K. and F. G. Ho Idaway 1950 Small scale field evaluation of insecticides for corn borer control. Jour. Econ. Ent. 43:433-433. Decker, G. C., J. W. Apple, J. M. Wright, and H. B. Petty 1947 European corn borer control on canning corn. Jour. Econ. Ent. 40:395-400. Fahey, J. E., T. A. Brindley, and H. W. Rusk 1953 Three years' study of DDT residues on corn plants treated for European corn borer control. Iowa State Coll. Jour, of Sci. 23:209-260. , T. A. Brindley, and M. L. Spear 1955 DDT residues in fat from steers pastured on corn stover in DOT-treated fields. Jour. Ecoi,. Ent. 48:606-60/. and H. W. Rusk 1951 Determination of DDT residues on corn. Analyt. Chem. 25: 1926-1929. 32

Fahey, J. E. , H. \!. Rusk, and H. C. Cox 1956 Residues on corn plants treated with DDT granules and emulsions for European corn borer control. Jour. Econ. Ent. 49:846-349. Farrar, M. 0. 1953 The granulated type insecticide for soil treatment. Jour. Econ. Ent. 46:377-379. Ficht, G. A. 1933 A progress report on some insecticides used against the European corn borer. Jour. Econ. Ent. 26:747-754. Gannon, Norman and G. C. Decker 1958 The conversion of heptachlor to its epoxide on plants. Jour. Econ. Ent. 51:3-7. Gould, George E. and /•!. Curtis V/ ilson 1957 Granulated insecticides For European corn borer control. Jour. Econ. Ent. 50:510-511. Muber, L. L., C. R. Neiswander, and R. M. Salter !923 The European corn borer and its environment. Ohio Agr. Exp. Sta. Bui. 429:105-106. Lovely, \i. G., H. C. Cox, and T. A. Brindley i956 Application equipment for granulated insecticides. Jour. Econ. ent. 43:339-34v. Pepper, B. B. and L. A. Carrutn l345 A new plant insecticide for the control of the European corn borer. Jour. Econ. Ent. 33:59--^. Questel, D. D. 1944 DDT as a substitute for derris against the European corn borer. Jour. Econ. Ent. 37:l49-l5O.

1945 The effects of DDT dust and spray preparations on larvae of the European corn borer. U. S. Dept. Agr. Bur. Ent. and PI. Quar. E-67I. and T. A. Brindley 1953 Small-plot tests of new insecticides in control of European corn borer, 1950-1951. Jour. Econ. Ent. 46:519-521. 5 imanton, F. L., F. F. Di eke, and G. T. Bottger 1931 The lethal power of certain insecticides tested in Michigan against the European corn borer. Jour. Econ. Ent. 24:395-404. Turner, N. 1936 Insecticides to control the European corn borer. Conn. (Mew Haven) Agr. Exp. Sta. Cir. 114:73-76. U. S. Agr. Res. Serv. and Fed. Ext. Serv. 1958 Insecticide recommendations of the Entomology Research Di­ vision for the control of insects attacking crops and live­ stock, 1953 season. U. S. Dept. Agr. Handbook 120. U. S. Code 1955 Title 21 , Part U0. 1953. 83

Vinal, S. C. 1917 The European corn borer, Pyrausta nub i1ali s (Hbn.), a recently established pest in Massachusetts. Mass. Agr. Exp. Sta. Bu 1. 173:147-152. Worthley, L. H. and 0. J. Caffrey 1927 Scouting, quarantine and control for the European corn borer, 1917-1926. U. S. Dept. Agr. Tech. Bui. >3. ACKNOWLEDGMENTS

The author is especially grateful to Dr. H, M. Harris for his counsel

and encouragement, and for the opportunity to continue my studies in grad­ uate school at lov/a State.

Sincere appreciation is extended to my major professor, Dr. T. A.

Brindley, for his help in organizing this research and his advice and constructive criticisms in the completion of this thesis. Appreciation is also extended to G. Lovely for his assistance in preparing and operat­

ing the granular applicator; to William F. Iv.vol ek and Donald Z isson Tor

their help in analyzing the data ; and to Jack E. Fahey for analyzing the residue samples.

For their assistance with various phases of the work associated with the development of this project, acknowledgment is made to James Harding,

Eugene King, Glenn Maus ton, Alton Sparks, and the entire staff of the

European Corn Borer Research Laboratory, Ankeny, Iowa.

Last but not least, my wife Shirley deserves special credit for the assistance, encouragement and understanding she has provided throughout my graduate studies. u5

APPENDIX 85

Tablé 19. Corn borer larvae and cavities found in corn at midsummer fol­ lowing the application of granular insecticides for first brood control, 1956.

Number cavities Number larvae Insecticide Replicate Replicate treatment 1 1 1 111 IV Tota 1 1 I | 1 1 1 IV Total (Pounds per acre)^ Treated June 20° DDT 1 1 2 4 2 9 0 3 7 5 15

Heptachlor 0.5 3 0 1 6 10 1 2 3 2 8 11 1.0 0 1 1 2 0 1 0 1 2 11 1.5 0 0 1 0 1 0 1 2 1 4

Toxaphene 1 l 0 1 3 5 2 1 6 3 12 I 1 2 0 2 1 4 7 0 1 1 4 6 i { 3 1 1 1 3 1 2 0 0 3

Endrin 0. 1 0 1 1 0 2 0 2 2 1 5 1 I 0.2 0 1 1 0 2 0 2 3 0 5 I 1 0.4 1 0 0 0 1 0 0 0 0 0

Untreated control 13 5 8 20 46 20 8 19 24 71

Treated June 25c DDT 1 1 0 2 2 5 1 0 3 1 5

Heptachlor 0.5 5 1 3 1 10 4 0 2 1 7 i 1 1.0 0 0 0 0 0 1 0 0 1 2 1.5 0 0 0 0 0 1 1 0 0 2

Toxaphene 1 2 2 6 7 17 1 2 4 4 1 1 {: 2 3 3 7 0 13 1 2 7 2 12 1 ; 3 3 1 0 1 5 2 4 0 1 7

Endr in 0.1 6 3 1 0 10 5 2 1 0 8 • t : 0.2 3 0 1 0 4 3 0 1 0 4 1 ( 0.4 1 1 0 0 2 1 1 0 1 3

Untreated control 13 9 27 11 60 15 1 1 27 12 65

aPounds per acre of actual insecticide

^Ten plants sampled per replicate on July 5

^Twenty plants sampled per replicate on July 6 37

Table. 20.. Corn borer larvae arid cavities found in corn in the fall fol­ lowing the application of granular insecticides for second brood controlj 1956.

Number cavities Number larvae . Insecticide Replicate Replicate treatment 1 || 111 IV Tota 1 1 11 111 IV Total (Pounds per acre)9 Treated July 31 DOT 1 7 8 8 2 25 8 7 8 3 26

Heptach1or 0.5 5 16 3 2 26 5 14 7 5 31 i I 1.0 6 10 6 9 31 5 13 10 11 39 J ! 1.5 15 15 5 8 43 16 16 3 12 47

Toxaphene 1 4 15 11 5 35 5 17 9 6 37 II 2 12 15 6 5 38 12 16 11 6 45 3 6 18 10 6 40 7 18 9 6 40

Endrin 0.1 8 10 7 10 35 8 12 7 10 37 11 0.2 8 4 8 7 27 9 3 14 5 31 J j 0.4 3 17 2 2 24 2 18 3 3 26

Untreated control 20 26 20 34 100 23 30 16 34 103

Treated August 7^ DDT 1 18 11 9 9 47 14 11 12 8 45

Heptachlor 0.5 4 11 12 6 33 9 12 17 8 46 1 i 1.0 2 4 2 4 12 2 4 3 8 17 i: 1.5 1 3 10 8 22 2 3 10 9 24

Toxaphene 1 14 6 12 12 44 21 8 12 13 54 t J 2 15 5 3 5 28 14 10 8 7 39 1 t 3 12 4 5 5 26 8 6 12 7 33

Endrin 0. 1 14 8 11 4 37 14 8 16 6 44 0.2 14 13 16 6 49 15 9 15 5 44 It 0.4 5 3 2 5 15 7 5 3 4 19

Untreated control 30 14 30 32 106 33 14 31 33 i,,

aPounds per acre of actual insecticide

^Ten plants sampled per replicate on September 14 Table 21. Corn borer larvae and cavities found in corn at midsummer fol­ lowing application of granular insecticides for first brood control, 1957.

Number cavities Number larvae Insecticide Repli cate Repli cate treatment 1 II III IV Total I II III IV Total (Pounds per acre)3 Treated June 27^ DDT 0.6 13 0 10 18 54 18 15 11 14 58

Heptachlor 0.5 11 14 0 5 30 10 S 0 4 23 1 i 1.0 3 5 1 0 9 3 3 l 0 7 11 1.5 3 1 1 0 5 3 1 l 0 5

Toxaphene 0.5 15 2 15 1 1 43 13 3 11 8 35 t I 1.0 15 5 9 1 1 40 13 5 9 8 35 1 Z 1.5 5 1 7 9 22 4 1 7 b 18 11 2.0 14 3 3 5 25 15 3 3 5 2o

Endrin 0. 1 16 2 6 13 37 12 2 5 9 23 1 ; 0.2 4 10 6 6 26 3 18 4 4 29 1 : 0.5 11 3 5 2 21 11 2 b 1 20

Untreated control 36 44 20 28 128 30 33 13 25 101

aPounds per acre of actual insecticide

'-'Ten plants sampled per replicate on July 24 89

Table 22. Corn borer larvae and cavities found in corn in the fall after application of granular insecticides for second brood control, 1957.

Number cavities Number la. fae Insecticide Replicate Replicate treatment 1 11 111 IV Total 1 1 1 111 .V Total (Pounds per acre)3 Treated August 7 DDT 1 34 19 25 19 97 22 14 20 17 73

Heptachlor 0.5 15 36 10 19 30 14 31 10 14 69 11 1.0 17 16 19 16 68 16 16 17 15 64 ii 1.5 14 18 18 9 59 15 16 17 3 56

Toxaphene 0.5 28 27 36 20 111 23 25 29 14 91 i1 1.0 23 25 29 12 94 25 19 21 13 78 11 1.5 22 23 33 11 94 18 24 30 10 82 11 2.0 23 18 25 20 86 21 13 21 20 75

Endrin 0. 1 20 16 11 10 57 17 18 9 8 52 iI 0.2 9 6 16 5 36 9 7 10 4 30 II 0.5 12 4 8 3 27 13 6 4 2 25

Untreated control 73 46 33 31 133 63 42 27 25 157

Treated August 1 DDT 1 21 27 15 15 78 17 19 10 11 57

Heptachlor 0.5 30 35 29 36 130 20 30 21 31 102 t ; 1.0 39 15 21 34 109 30 12 15 25 82 Ii 1.5 22 36 19 15 92 20 30 15 18 83

Toxaphene 0.5 26 27 30 22 105 20 26 23 15 34 1 1 l.O 37 20 23 13 93 40 18 20 12 90 1 1 1.5 26 36 43 35 140 23 32 33 22 110 I1 2.0 24 22 25 13 34 21 16 25 9 71

Endrin 0. 1 37 28 11 26 102 26 20 9 16 71 1I 0.2 25 22 10 22 79 24 17 13 16 70 11 0.5 20 33 27 36 116 18 37 23 37 115

Untreated control 23 41 43 48 155 22 39 39 36 136

aPounds per acre of actual insecticide

^Ten plants sampled per replicate September 13 90

Table 23. Corn borer larvae and cavities found in corn at mi ds.ummer fol­ lowing application of granular insecticides for first brood control, 1953.

Number cavities Number larvae Insecticide Replicate Replicate treatment 1 1 1 1 1 1 IV Total 1 I 1 I 1 1 IV Tota ! (Pounds per acre)d Treated June 23 DDT 1 0 0 I 0 1 0 0 I 0 1

Endr in 0.125 1 0 0 2 3 1 0 0 2 3 iI 0.25 0 1 1 0 2 0 0 2 1 3 1 . 0.5 0 0 2 2 4 0 0 1 0 1

Heptachlor 0.5 0 0 2 0 2 0 0 1 0 1 :1 0.75 2 0 0 1 3 2 0 0 1 3 SI 1.0 0 0 2 0 2 0 0 2 0 2

Toxaphene 1.0 1 1 1 0 3 1 1 0 0 2 ;l 1.5 0 1 1 1 3 0 1 0 1 2 t { 2.0 0 0 1 2 3 0 0 1 1 2

Untreated control 12 14 10 6 42 11 9 12 4 36

Treated July 2^ DDT 1 0 2 0 3 11 3 1 0 1 5

Endrin 0.125 13 2 2 3 20 7 3 1 0 11 I 1 0.25 5 10 0 5 20 1 1 0 1 3 I ! 0.5 6 2 2 3 13 1 0 0 2 3

Heptachlor 0.5 4 4 1 3 12 1 2 0 3 6 1 J 0.75 4 2 1 3 10 1 2 0 2 5 : 1 1.0 2 0 4 2 8 0 0 1 2 3

Toxaphene 1.0 6 2 7 0 15 2 1 2 0 5 11 1.5 2 2 0 3 7 1 1 0 1 3 1 i 2.0 4 2 2 7 15 0 3 1 4 8

Untreated control 10 3 5 6C 24 5 2 1 3C 11

aPounds per acre of actual insecticide

&Ten plants sampled per replicate July 21

^"Estimated values; actual values missing 91

Table'24. -Cor-n. borer cavities in corn in the fall following application of granular Insecticides for second brood control, 1958.

Number cavities Insecticide Replicate treatment 1 11 111 IV Total (Pounds per acre)3 Treated August 7 Toxaphene 1.0 1 15 4 9 29 1 1 1.5 6 9 4 8 27 I1 2.0 6 5 10 3 24

Heptachlor 0.5 3 7 7 5 22 I 1 0.75 6 5 7 8 26 i ; 1.0 2 10 3 5 20

Endrin 0.125 5 3 8 6 22 1 i 0.25 1 10 12 10 33 I i 0.5 2 5 9 4 20

DDT 1 2 II 7 5 25

Untreated control 13 32 18 30 93

Treated August 1 s'3 Toxaphene 1.0 11 7 19 15 52 I 1 1.5 3 6 9 11 29 ii 2.0 13 5 22 5 45

Heptachlor 0.5 5 4 11 3 23 i: 0.75 6 7 12 4 29 it 1.0 7 3 3 2 15

Endrin 0.125 4 7 9 9 29 1 i 0.25 10 11 2 8 31 I I 0.5 11 2 10 11 34

DDT 1 15 13 14 11 53

Untreated control 27 30 17 29 103

aPounds per acre of actual insecticide

^Ten plants sampled per replicate September 26. Table 25. Insecticide residues on whorl leaves, whorls, stalk leaves, and stalks one day aftér application of granular insecticides for first brood control, 1956.

Whorl leaves Whorl Stalk 1 eaves Stalk and axi1 Tota 1 of plant parts Rep1i- Sample Sample Sample Sample Tota 1 Tota 1 cate Residue weight Residue weight Residue weight Res idue weight weight res idue Residu (p.p.m.) (gm.) (p.p.m.) (gm. j (p.p.m. ) (gm.) (p.p.m.) (gm. ) (gm. ) (gm. ) (p.p.m

Treated June 20, Sampled June 21

DDT 1 pound per acre ' 1 2.0 298 36.8 342 0.8 342 19.0 1042 2024 .033255 16.4 II 1.1 236 27.7 282 1.0 288 6.9 917 1723 .014686 8.5 III 0.1 254 42.3 248 0.8 337 6.7 1080 1919 .018021 9.4 IV 0.8 273 1. 1 268 <0. 1 313 <0. 1 1061 1915 .000651 0.3 > o é 27.0 0.7 8.2 8.7

Heptachlor 0.5 pound per acre 1 1.0 300 29.5 329 CO. 1 360 6.0 1046 2035 .016318 , 8.0 II 0.2 238 30.8 273 <0. ] 349 6.8 1 10b 1966 .016012 8.1 III 1.0 240 40.4 273 0.5 221 3.6 981 1715 .01491 1 : 8.7 IV 0.5 251 67.4 240 0.3 244 8.8 902 1&37 .024312 14.9 Avg. 0.8 42.0 0.2 6.3 , 9.9

Heptachlor 1 pound per acre 1 2.0 2b5 70.9 303 <0. 1 371 9.1 1 150 2089 .032515 15.6 1 1 0.8 225 47.0 217 0.3 295 13.2 759 1496 .020486 13.7 III 0.6 259 2.0 259 0.3 290 12.5 905 1713 .012073 7.0 IV 3-0 185 21.5 220 D 0.4 212 3.7 968 1585 .008951 5.6 < > C 35.4 0.3 9.6 . 10.5 Tab)e 25. (Continued)

Whorl 1 eaves Whorl Stalk 1 eaves Stalk and axi1 Total of plant parts Repli- Sample Sample Sample Sample Total Tota 1 cate Residue weight Res idue weight Residue weight res idue Residue (p.p.m. ) (gm.) (p.p.m.) (gm. ) (p • p • m• ) (gm.) .p.m. ) (gm.) (gm. ) (gm. ) (p.p.m.)

Heptachlor 1.5 pounds per acre 1 1.3 280 80.0 276 8.5 323 19.2 994 1873 .044274 23.6 11 2. 1 267 55.5 305 0.3 309 9.4 1075 1956 .027686 14.2 III 1.8 244 38.5 312 0.2 284 4.0 1044 1884 .016684 8.9 IV 0.7 216 35.1 234 0.4 208 0.3 671 1329 .008649 6.5 Avg. 1.5 42.3 2.4 8.2 13.3

Toxaphene 1 pound per acre 1 4.0 302 32.7 339 2. 6 353 10.0 1201 2195 .025221 11.5 II 9.2 228 44.1 272 3.9 309 10.6 947 1756 .025336 14.4 III 11.1 215 43.6 287 1.1 316 10.6 943 1761 .026678 15.1 IV 9.4 255 32.8 229 3.0 281 4.7 1024 1789 .015564 8.7 Avg. 8.4 39.6 2.7 9.0 12.4

Toxaphene 2 pounds per acre 1 12.5 244 93.8 288 9.4 327 47.6 921 1780 .0769/8 43.2 11 18.9 285 44.1 363 13.8 326 28.9 1 164 2138 .059533 27.8 III 16.2 215 67.4 264 5.4 279 17.3 1020 1778 .040429 22.7 : IV 10.4 293 57.9 318 5.4 364 Lost 1154 - - _ ' 0 Avg. 14.4 65.8 8.5 31.3 31. 2f

Toxaphene 3 pounds per acre 1 9-5 208 162.0 216 4.6 328 83.6 929 1631 .116141 69.1 II 12.6 242 87.5 313 6.5 306 25.8 1 126 1987 .061477 30.9 III 13.2 263 1 10.4 317 2.7 311 25.8 1037 1928 .066063 34.3 IV 20.6 262 188.0 249 4.9 306 49.6 963 1780 .101473 57.0 Avg. 14.0 137.0 4.7 46.0 47.8 Average of three replicates Table 25. (continued)

Whorl leaves Whorl Stalk leaves Stalk and axi1 Total of plant parts Repli- Sample Sample Sample Sample Total Total cate Residue weight Residue weight Residue weight Residue weight weight residue Residue (p.p.m.) (gm.) (p. p.m. ) (gm.) (p.p.m.) (gm. .p.m.) (gm. ) (gm. ) (gm. ) (p.p.m.

Treated June 25, sampled June 26

DDT 1 pound per acre 1 0.6 254 49.8 307 0.5 307 6.5 1 109 1977 .022803 11.5 1 1 0 218 45.5 330 Lost 224 16.3 845 1617 - III 0 175 26.8 179 0.6 158 2.3 898 1410 .006957 4.9 IV 0 179 10. 1 178 0.4 135 4.5 1009 1501 .006392 4.3 Avg. 0.2 33.1 0.5 7.4 6,9

Heptachlor 0.5 pound per acre 1 • <0.1 268 44.0 341 CO. 1 231 Lost 1161 2001 _ II <0.1 305 23.6 381 Co. 1 230 1.3 1144 2060 .010532 5.1 III <0.05 191 4.8 223 <0. 1 193 Lost 1096 1703 - - • IV <0.1 247 7.1 144 X0.1 139 Lost 735 1265 - - Avg. <0.1 19.9 <0. 1 1.3 5.1

Heptachlor 1 pound per acre 1 <0. 1 26? 45.8 334 CO. 1 287 Lost 1082 1970 II <0.1 230 34.9 298 0.3 298 Lost 1189 2015 - - • III <0.1 195 40.8 197 <0. 1 181 1. 1 1005 1578 .009180 5.8 IV <0.1 261 76.0 296 <0.1 162 Lost 769 1488 - - : Avg. <0.1 49.4 CO. 1 1.1 5.8 Table 25. (continued)

Whorl leaves Whorl Stalk leaves Stalk and axi1 Total of plant parts Repli- Sample Sample Sample Sample Total Total cate Residue weight Residue weight Residue weight (p.p.m.) (gm. ) (p.p.m. ) (gm. ) (p.p.m.) (gm (p.p.m. ) (gm.) (gm. ) (gm. ) (p. p.m.) Heptachlor 1.5 pounds per acre 1 <0. 1 257 106.8 410 <0. 1 243 12.7 1076 1986 .057503 29.0 .11 <0.1 232 29.0 242 <0. 1 209 4.9 1034 1717 .012128 7.1 111 <0.1 188 102.2 182 <0. 1 182 39.6 732 1284 .047625 37.1 IV <0.1 225 131.6 173 <0. 1 189 Lost 719 1306 Avg. <0.1 92.4 <0. 1 19.1 24.4 • Toxaphene 1 pound per acre

1 5.5 217 68.7 1.1 216 - V) 345 Lost 972 1750 VI II 13.6 198 38.3 196 2.0 178 6.4 781 1353 .015554 11.5" III 4.5 201 22.5 120 6. 6 183 11.2 1017 1521 .016203 lO.f IV 4.4 272 47.4 196 5.3 158 4.9 1301 1927 .017700 9/2 Avg. 7-0 44.0 3.8 5.6 10.(5

Toxaphene 2 pounds per acre 1 9.0 219 156.5 299 8.8 224 18. 7 901 164-3 .067584 4lj. 1 II 14.2 189 112.0 325 6.4 187 9.1 950 1651 .048926 2^.6 III 5.4 224 246.5 142 Lost 142 14.5 729 1237 - IV 5-7 202 142.2 232 6.0 140 13.4 642 1216 .043585 3^.8 Avg. 8.6 164.3 7.1 13.9 35.5 a Toxaphene 3 pounds per acre 1 9.6 251 158.2 335 10. 1 267 12.0 917 1770 .069107 39|0 II 11.3 213 108.7 335 5.9 255 0 736 1539 .040326 26i.2 III 33.6 168 395.7 138 27.8 108 4.6 870 1284 .067256 52.-4 IV 20.8 185 147.4 247 27.8 138 5. 1 990 1560 .049141 31.5 Avg. 18.8 202.5 17.9 7.2 371 96

Table 26. Insecticide residues following application of granular insecti­ cides for first brood control, 1956.a

Residue in parts per million Rate per Repl icate Insect!c ide acre 1 11 111 IV Mean (Pounds)

Sampled August 10

DDT 1 0.9 0.6 0.8 0.4 0.7

Heptachlor 0.5 <0. 1 (0. 1 <0.1 <0.1 <0.1 1.0 <0.1 <0. 1 <0. 1 <0. 1 <0. 1 1.5 <0. 1 <0. 1 <0. 1 <0. 1 <0.1

Toxaphene 1.0 0.71 0.63 0.69 0. 1 1 0.54 2.0 1.93 0.76 1.38 0.88 1.24 3-0 2.01 1.97 2.06 3.29 2.33

Sampled October 2

DDT 1 0.7 0.9 0.8 0.4 0.7

Heptachlor 0.5 <0.1 <0. 1 - - <0.1

1.0 <0. 1 <0. 1 - - <0.1 1.5 <0. 1 <0. 1 - - <0. 1

Toxaphene 1.0 0.60 1.65 - - 1.13 2.0 2.78 2.78 - - 2.78

3.0 4.10 4.97 - 4.54

^Applications made June 25 Table 2/. Insecticide residues on the stalks, leaves, and husks one day after application*of granular insecticides for second brood control, 1956.

Stalk Leaves Husks Total of plant parts Repli- Sample Sample Sample Tota 1 Total • T reatment cate Residue weight Resi due weight Residue weight weight res idue Res idue (Pounds per acre) (p.p.m. ) (gm.) (p.p.m. ) (gm.) (p.p.m. ) (gm.) (gm. ) (gm. ) (p.p.m.

Treated July 31, sampled August 1

DDT 1 1 3.5 725 1.2 425 1.5 416 1566 .OO3672 2.3 1 1 1.0 1022 0.7 532 0. 8 768 2322 .002009 0.9 I| | 2.2 1005 0.5 438 1.0 353 1796 .002733 1.5 IV 0.8 918 0.5 421 0.7 366 1705 .001201- 0.7 Avg. 1.9 0.7 1.0 1.4

Heptachlor 0.5 1 1.5 889 0.8 438 Lost 533 I860 — - 1 1 1.9 1045 <0.1 469 <0. 1 584 2098 .002091' 1.0 1 1 1 1.1 977 <0. 1 427 /0. 1 545 1949 .001172 0. 6 IV 0.5 987 to. 1 362 <0. 1 3 25 1674 .000562 0.3 Avg. 1.3 0.2 <0. I 0. 6

Heptachlor 1 1 5.8 804 1.5 461 0. 8 271 1536 .005572 3.6 1 1 1.7 1018 0.4 528 0.5 560 2106 .002222, 1.1 1 1 1 4.7 930 <0.1 439 0.5 494 1918 .004397- 2.6 IV 2.9 879 <0. 1 392 <0.1 484 1755 .002637 1.5 Avg. 3.3 0.5 0.5 2.2

Heptachlor 1.5 1 5.3 870 2.4 471 0.1 517 1858 .005793 3.1 1 1 4.2 1005 0.3 397 0.4 578 1980 .004571 " 2.3 1 1 1 4.2 1058 <0.1 428 0.3 499 1985 .004636 , 2.3 IV Lost 835 < 0.1 373 <0.1 557 - Avg. 4.4 0.7 0.2 , ' 2.6 Table 27. (continued)

Stalk Leaves Husks Total •of plant parts Rep)i- Sample Samp 1e Sample Total Jotal T reatment cate Residue weight weight residue Resi due (pounds per acre) (p.p.m.) (gm. ) (p.p.m. ) (gm. (p.p.m.T (gm.) (gm.') (gm. ) (p.p.m.)

Toxaphene 1 1 0. 6 980 7-5 431 ' 6.4 375 1786 » .006221 3.5 1 1 0, 1118 5.0 491 7.0 516" Z125 .006067 2.9 111 0 916 22.7 397 8.1 452 1765 " .012673 7.2 IV 0.7 913 26.0 439 15.1 239° 1591 .015662 9.8 Avg. 0.3 15.3 9.2 5.9 Toxaphene 2 1 12.8 863 5.8 447 17.4 527 1837 .022809 12.4 I| 3.8 937 3.9 378 , 7.6 451 1766 .008462 4.8 I| | 0 969 16.2 461 Lost 474 1904 - - IV 2.5 965 13.3 435 5.6 578 1978 .011435 5.8 Avg. 4.8 9.8 10. 2 7.7

Toxaphene 3 1 3.7 930 5.6 437 9.8 273 1640 .008564 5.2 1 1 5.0 1037 4.4 444 18.2 550 2031 .017149 8.4 1 1 1 1.1 1138 3.9 507 11.5 510 2155 .009094 4.2 IV 5.9 1016 12.9 461 8.1 451 1928 .015594 8.1 Avg. 3.9 7.0 11.9 6.5 Treated August 7, sampled August 8

DDT 1 1 1.5 842 1.7 419 0.4 645 1906 .002233 1.2 I| 1.7 831 0.2 402 0.5 721 1954 .001854 0.9 I || 0.1 1049 0 417 0.1 524 1990 .000157 0.08 IV 0 961 0.2 475 0. 1 758 2194 .000171 0.08 Avg. 0.9 0.5 0.3 0.6 Table 27. (continued)

Stalk Leaves Husks Total of plant parts Repli- Sample Sample Sample Tota 1 Total Treatment cate Residue weight Residue weight Res idue weight weight res idue Res idue (Pounds per acre) (p.p.m.) (gm.)(p.p.m.)(gm.) (p.p.m. ) (gm.) (gm. ) (gm. ) (p.p.m..

Heptachlor 0.5 1 0.2 893 <0.1 428 <0. 1 740 2061 .000295 0. 1 1 1 0.5 885 <0.1 431 0. 1 642 1958 .000550 0.3 1 || 0.8 828 <0. 1 448 <0. 1 563 1839 ,000764 0.4 IV 0.2 849 <0. 1 448 <0. I 637 1934 .000278 0.1 Avg. 0.4 <0. 1 <0. 1

Heptachlor l 1 1.2 868 <0. 1 364 0.9 625 1856 .001641 0.9 1 1 1.0 897 <0. 1 382 0.2 585 1864 .001052 0.6 1 1 1 0.6 981 Co. 1 471 <0.1 600 2052 .000696 0.3 IV 0.7 1122 -co. 1 530 Lost 725 2377 - - Avg. 0.9 <0. 1 0.4 0.6

Heptachlor 1.5 1 1.5 1012 0.1 46.1 0.8 ' 733 2206 .002151 1.0 1 1 1.4 845 0.1 396 0.7 615 1856 .001653 0.9 1 1 1 Lost 963 <0. 1 459 Lost 680 2102 - - IV 1.5 995 <0.1 490 0.3 783 - ' 2268 .001776 0.8 Avg. 1.5 0.1 0.5 0.9

Toxaphene 1 1 4.9 886 6.1 399 8.7 758 2043 .013370 6. 5 1 1 7.7 666 1.2 365 10.2 574 1605 .011421 7.1 I || 7.5 ' 805 5.4 626 11.2 455 1886 .014514 7.7 IV 3.0 952 3.6 480 9.4 664 2096 .010826 5.2 Avg. 5.8 4.1 9.9 6.6 Table 27. (continued)

Stalk Leaves Husks Total of plant parts Repli- Sample Samp 1e Sample Total Total Treatment cate Resi due weight Residue weight Res idue weight weight residue Res idue (Pounds per acre) (p.p.m. ) (gm.) (p.p.m. ) (gm.) (p.p.m.) (gm. ) (gm. ) (gm. ) (p.p.m.)

Toxaphene 2 1 9.0 1061 2.9 509 2.3 900 2470 .013095 5.3 1 1 4.6 971 4.7 420 11.3 774 2165 .015187 7.0 1 1 1 9.4 762 1.8 402 9.9 700 1864 .014816 7.9 IV 8.4 783 2.4 391 6.5 729 1903 .012254 6.4

Avg. 7.9 3.0 5.0 • 6.7

Toxaphene 3 1 7.1 731 7.5 327 5.3 613 1671 .010892 6.5 1 1 9.8 675 1.6 375 9.7 660 1718 .013695 8.0 1 ! 1 2.8 750 4.9 399 6.8 530 1679 .007659 4.6 IV 7.9 881 4.0 484 6.8 636 . 2001 .013221 6.6 Avg. 6.9 4.5 7.2 6.4 101

Table 28. Insecticide residues following application of granular insecti­ cides for second brood control, 1956.a

Residue in parts per million Rate per Repl icate 1nsectici de acre 1 11 11 1 IV Mean (Pounds)

Sampled Auqust 21

DDT 1 0.1 2. 1 1.0 0.3 0.9

Heptachlor 0.5 <0. I <0. 1 <0. 1 0.2 0. 1 1.0 0.5 1.1 Lost 0.5 0.7 1.5 0.7 I.I 1.8 <0. 1 0.9

Toxaphene 1 1.7 3.7 2.8 1.5 2.4 2 2.2 5.7 6.2 3-5 4.4 3 2.4 12.3 2.5 1.6 4.7

Sampled October 13

DDT t 0.8 1.0 1.2 0.7 0.9

Heptachlor 0.5 <0.05 <0.05 <0.05 <0.05 <0.05 1.0 0.48 <0.05 <0,05 <0.05 0.12 1.5 <0.05 <0.05 <Û.05 <0.05. <0.05

Toxaphene 1 0.6 1.0 2. 1 - 1.2 2 5.2 5.2 • 3.7 5.4 4.9 3 3.5 3.3 3.3 4.6 3.9

^Applications made July 31 102

Table 29. Insecticide residues following application of granular insecti­ cides for first brood control, 1957.a

Residue in parts per mi 11 ion Rate per Sampling Replicate 1nsecticide acre date 1 1 1 1 1 1 IV Mean (Pounds)

DDT 0.6 6/28 1.0 0.7 1.2 1.4 1.1 7/30 0 6.5 0 0 1.6 9/3 0.7 0.7 1.7 1.0 1.0 9/24 0.2 0.5 0.7 - 0.4

Heptachlor 1 6/28 3.3 5.5 3.2 8.0 5.0 7/30 <0.1 <0.1 <0. 1 <0. 1 <0. 1 9/3 <0. 1 <0.1 <0. 1 <0. 1 <0. 1 9/24 < 0. 1 £0. 1 <0. 1 <0. 1 <0. 1

Toxaphene 2 6/28 14.6 19.1 10. 1 14.6 14.6 7/30 0 2.2 0.2 2.7 1.3 9/3 2.5 0.5 2. 2 4.3 2.4 9/24 3.6 2.2 1.0 1.4 2.1

^Applications made June 27 103

Table 30. Insecticide residues following application of granular insecti­ cides for second brood control, 1957.a TO CD to i due in parts per mi 11 ion Rate per Sampling Replicate 1nsectic ide acre date I 1 1 1 11 IV Mean (Pounds)

DDT 1 3/15 5.5 7. 3 8.8 13. 8 9.0 9/16 7.0 6. 7 4.8 3- 8 5.6 10/19 5.4 3. 7 8.6 2. 2 5.0

Heptachlor 1 8/15 1.2 0. 8 2.2 1. 4 1.4 9/16 <0.01 <0. 01 <0.01 <0. 01 <0.01 10/19 <0.01

Toxaphene 2 8/15 13.6 9. 8 11.2 11. 9 11.6 9/16 2.4 4. 0 4.5 3. 2 3.5 10/19 6.9 1. 2 3.4 0 2.9

^Application made August 14 104

Table 31. Insecticide residues following application of granular insecti­ cides for first brood control, 1958.a

Res idue in parts per million Rate per Sampling Replicate 1nsecti ci de acre date 1 1 1 11 1 IV Mean (pounds)

DDT 1 6/24 38.1 21.2 41.9 43.4 36.2 7/23 0.3 0.9 0.8 1.7 0.9 9/19 0.6 0.3 0.2 0.3 0.4

Heptachlor 0.75 6/24 1.9 5.3 3.9 3.4 3-8 7/23 <0.05 <0.05 <0.05 <0.05 <0.05 9/19 <0.05 <0.05 <0.05 <0.05 <0.05

Toxaphene 1.5 6/24 6.5 9.6 4.4 b. 0 0.6 7/23 1.0 0.9 0 0.8 0.7 9/19 0.9 1.7 0 0.9

^Applications made June 23

Table 32. Insecticide residues following application of granular insecti­ cides for second brood control, 1958.a

Residue in parts per million Rate per Sampling Replicate 1 nsecti ci de acre date I 1 1 111 IV Mean (pounds)

DDT 1 3/19 1.8 0.4 0 0.8 0.8 9/16 2.0 1.9 1.1 1.1 1.5 10/14 1.2 1.3 1.7 2. 1 1.6

Heptachlor 0.75 8/19 0.83 0.62 0.48 0.62 0.64 9/16 0.07 0.14 0.11 0.25 0.14 10/14 0.08 0.07 0.11 0. 1 1 0.09

Toxaphene 1.5 8/19 3-2 1.9 2.8 3.7 2.9 9/16 1.5 1.4 1.4 1.7 1.5 10/14 1.6 0.9 1.3 2.4 1.6

Applications made August 18