the effects of herbicides and insecticides used and

V

THE EFFECTS OF HERBICIDES AND INSECTICIDES USED

ALONE AND IN COMBINATION ON THE GROWTH

AND DEVELOPMENT OF CORN

by

MARIA FITRIANA, B.S.

A THESIS

IN

CROP SCIENCE

Submitted to the Graduate Faculty of Texas Tech University in

Partial Fulfillment of the Requirements for

the Degree of

MASTER OF SCIENCE

May, 1991

y^

cic:i_

Mo.-

-^' ACKNOWLEDGEMENTS

I would like to express my sincere appreciation and

gratitude to my committee, Dr. Norman W. Hopper and Dr. Wayne

Keeling, for their guidance, patience, helpful suggestions,

understanding, and friendship during the entire time of my

study in the U.S. I also wish to thank Dr. Steve Fraze for

his help and suggestions while serving as member of my

committee.

I would like to thank to Dr. Marvin Cepica, who has been

very helpful in arranging my graduate work. I also wish to

thank several graduate students for their assistance, namely

Mohamed Mounsif, Nelson A. Rolong, and Bingru Huang.

A special thanks is extended to my husband, Ishak Thayeb,

for his patience, encouragement, support, and his

understanding during my study. I wish to thank my children,

Dodi Muhammad Reza, Muhammad Revi Febiansyah, Shendi Sentani,

Adelin Indah Marisa, and my sisters and my mother for their

support, encouragement, and their help.

11

1¥

CONTENTS

ACKNOWLEDGEMENTS ii

TABLES iv

CHAPTER

I. INTRODUCTION 1

II. LITERATURE REVIEW 4

Corn 4

Sorghum 6

Herbicides and Insecticides 7

III . MATERIALS AND METHODS 14

Hybrids 14

Greenhouse Study 14

Field Study 20

IV. RESULTS AND DISCUSSION 24

Greenhouse Study 24

Wet Weight 2 4

Dry Weight 2 5

Corn Height 2 9

Sorghum Injury 34

Field Study 37

Plants per Square Meter for Dekalb 711 37

Corn Height for Dekalb 711 39

Plants per Square Meter for Pioneer 3168 ... 44

Corn Height for Pioneer 3168 46

Plants per Square Meter for Triumph 2020 ... 50

Corn Height for Triumph 2020 52

V. SUMMARY AND CONCLUSIONS 58

1 1 1

Kv

Greenhouse Study 58

Field Study 59

LITERATURE CITED 60

APPENDICES

Greenhouse Study 64

A. Wet Weight 65

B. Dry Weight 68

C. Corn Height 4 Weeks after Planting 71

D. Corn Height 6 Weeks after Planting 74

E. Corn Height 8 Weeks after Planting 77

F. Sorghum Injury 80

Field study 83

G. Plants per Square Meter for Dekalb 711 ... 84

H. Corn Height for Dekalb 711 86

I. Plants per Square Meter for Pioneer 3168 . 90

J. Corn Height for Pioneer 3168 92

K. Plants per Square Meter for Triumph 2020 . 96

L. Corn Height for Triumph 2020 98

IV

TABLES

1. Insecticides, application rates, and time of application for the greenhouse and field study 16

2. Herbicides, application rates, and time of application for the greenhouse and field studies 17

3. Sources of variation and degrees of freedom for the analysis of variance for the greenhouse study 19

4. Sources of variation and degrees of freedom for the analysis of variance of each corn hybrid in the field study 23

5. Effect of hybrid and herbicide on corn wet weight at harvest (averaged over all insecticide means) for the greehouse study 25

6. Effect of hybrid and herbicide on corn dry weights (averaged over all insecticide means) for the greenhouse study 27

7. Effect of hybrid and herbicide on corn height when measured 4 weeks after planting (averaged over all insecticide means) for the greenhouse study 31



10. Effect of hybrid and herbicide on sorghum injury (averaged over all insecticide means) in the greenhouse study 35

11. Effect of herbicide and insecticide on the number of plants per square meter of Dekalb 711 in the field study 38

12. Effect of herbicide and insecticide on corn heights when measured 4 weeks after planting of Dekalb 711 in the field study * 40

V

13. Effect of herbicide and insecticide on corn height when measured 6 weeks after planting of Dekalb 711 in the field study 41

14. Effect of herbicide and insecticide on corn heights when measured 8 weeks after planting of Dekalb 711 in the field study 43

15. Effect of herbicide and insecticide on the number of plants per square meter of Pioneer 3168 in the field study 45

16. Effect of herbicide and insecticide on corn heights when measured 4 weeks after planting of Pioneer 3168 in the field study 47

17. Effect of herbicide and insecticide on corn heights when measured 6 weeks after planting of Pioneer 3168 in the field study 48

18. Effect of herbicide and insecticide on corn heights when measured 8 weeks after planting of Pioneer 3168 in the field study 4 9

19. Effect of herbicide and insecticide on the number of plants per square meter of Triumph 2020 in the field study 51

20. Effect of herbicide and insecticide on corn heights measured 4 weeks after planting of Triumph 2020 in the field study 53



Al. Analysis of variance for corn wet weight at harvest in the greenhouse study 66

A2. Effect of insecticide and herbicide on corn wet weight in the greenhouse study 67

Bl. Analysis of variance for corn dry weight at harvest in the greenhouse study 6 9

VI

B2. Effect of insecticide and herbicide on corn dry weights in the greenhouse study 70

CI. Analysis of variance for corn height measured 4 weeks after planting in the greenhouse study 72

C2. Effect of insecticide and herbicide on corn heights measured 4 weeks after planting in the greenhouse study 73

Dl. Analysis of variance for corn height measured 6 weeks after planting in the greenhouse study 75

D2. Effect of insecticide and herbicide on corn heights measured 6 weeks after planting in the greenhouse study 7 6

El. Analysis of variance for corn height measured 8 weeks after planting in the greenhouse study 78

E2. Effect of insecticide and herbicide on corn heights measured 8 weeks after planting in the greenhouse study 7 9

Fl. Analysis of variance for residual sorghum injury in the greenhouse study 81

F2. Effect of insecticide and herbicide residue on sorghum injury in the greenhouse study 82

Gl. Analysis of variance for the number of plants per square meter of Dekalb 711 in the field study 85

HI. Analysis of variance for corn height measured 4 weeks after planting of Dekalb 711 in the field study 87

H2. Analysis of variance for corn height measured 6 weeks after planting of Dekalb 711 in the field study 88

H3. Analysis of variance for corn height measured 8 weeks after planting of Dekalb 711 in the field study 89

II. Analysis of variance for number of plants per square meter of Pioneer 3168 in the field study 91

Jl. Analysis of variance for corn height measured 4 weeks after planting of Pioneer 3168 in the field study ... 93

J2. Analysis of variance for corn height measured 6 weeks after planting of Pioneer 3168 in the field study ... 94

vii

J3. Analysis of variance for corn height measured 8 weeks after planting of Pioneer 3168 in the field study ... 95

Kl. Analysis of variance for number of plants per square meter of Triumph 2020 in the field study 97

LI. Analysis of variance for corn height measured 4 weeks after planting of Triumph 2020 in the field study ... 99

L2. Analysis of variance for corn height measured 6 weeks after planting of Triumph 2020 in the field study .. 100

L3. Analysis of variance for corn height measured 8 weeks after planting of Triumph 2020 in the field study .. 101

Vlll

CHAPTER I

INTRODUCTION

Corn as we know it today is probably the most domesticated

of all field crops. Its existence is totally dependent on

man and it cannot exist as a wild plant for more than 2 to 3

generations. Corn ranks after wheat and rice as the third

most important crop in the world. In terms of world

production, the U.S. stands alone. The U.S. produces 47% of

the total world output on 23% of the world acreage (13).

Several factors that can reduce corn production are

weather, soil fertility, diseases, insects, weeds or other

factors that prevent the plants from operating at maximum

efficiency. Weeds have been known as a natural competitor of

desired growing crops since man began to cultivate the soil.

Weeds cause reductions of crop yield by being in competition

for light, moisture, nutrients, and space (1,3) . For

centuries, man has used mechanical, cultural, and biological

tools as his principal means of combating weeds. In the

present century, particularly the past 45 years, man has

found that chemicals can be utilized to control undesirable

plants in agronomic crops. Chemicals used for weed control

are called herbicides.

Herbicides are classified into two broad classes. They

are either selective or nonselective with respect to the

kinds of plants they kill. Selective weed killers are

herbicides that are more toxic to some plants than to others

while nonselective herbicides are toxic to all plants.

Therefore, their use is limited. The use of herbicides in

which the selective phytotoxicity of the phenoxy group of

chemicals was established, has been in existence since 1944

(2,12) . Chemicals used for controlling weeds may be soil

applied or foliar applied depending on the mode of action of

each chemical. Eventually the chemical may reach the soil

with either method of application. Residues from these

chemicals may persist in the soil for a year or more.

However, herbicidal activity is desirable only up to the time

the herbicides have achieved their intended purpose. Longer

persistence posses a hazard to subsequent land use and is

undesirable (2) .

Another natural enemy of a growing crop is insects.

Insects damage plants by feeding on all plant parts from the

seedling stage to maturity and act as vectors of plant

pathogens (20). The use of insecticides is one method of

combatting insects. In many cases, chemical control must be

supplemented with other measures.

The combination of pesticides is a common practice to

improve the efficiency of modern agriculture. Indications of

synergism between applied nutrients and pesticides have been

observed in many crops (38). Interaction between N

fertilizers and soil applied granular insecticides has been

thought to be a method of maximizing N-use efficiency in

rice. Several workers have reported increased uptake of

nutrients, improved growth and increased yields in many crops

as a result of systemic chemical application (38). The

insecticides not only destroy the insect, but should not be

harmful to plants, animals, or man. Some plants are more

susceptible to injury from insecticides than others (6). The

use of two or more chemicals in controlling weeds can cause a

synergistic effect on weeds, but it can also cause an

antagonistic interaction (28).

The objectives of this study were:

1. To evaluate any phytotoxic effects on three corn hybrids

from the use of two sulfonylurea herbicides and three

insecticides used alone and in combination.

2, To determine any residual effects of the herbicides and

insecticides used in this study on subsequent sorghum growth.

CHAPTER II

REVIEW OF LITERATURE

Corn

According to Martin, Leonard, and Stamp (27), corn is the

most completely domesticated of all field crops. It has a

remarkable diversity of vegetative types, with the result

that genotypes adapted to a wide range of environmental

conditions are in cultivation. The crop originated in

Mexico. It is a coarse annual grass belonging to the tribe

Maydeae, family of Gramineae. It grows from below sea level

to altitudes of 3963 meters. Some small, early varieties

only two feet tall, bear 8 to 9 leaves and are able to

produce mature grain in 50 days. Others with 42 to 44 leaves

and growing 6 meters tall require as few as 330 days to come

to maturity. In the United States, corn hybrids or varieties

grown in the Northern States are 1 to 2.5 meters tall, mature

in 90 to 120 days and may develop several tillers. The

greatest region producing corn in the United States has a

mean summer temperature of 70° to 80^ F (2lO-270 C) , a mean

night temperature exceeding 58° F (13° C), and a frost-free

season of over 140 days. An average June-July-August

temperature of 68° to 72° F (200-21° C) seems to be most

favorable for maximum yields.

Corn flowers and ripens more quickly at 80° F (27° C) .

The minimum temperature for the germination and growth of

corn is about 50° F (10°C). Corn is grown extensively in hot

climates, but yields are reduced where the mean summer

temperatures are above 80° F (27^0. Accelerated respiration

will exist with warm night temperatures. It will reduce the

carbohydrates and the dry weight of the plants. Corn

requires 60 to 100 cm of annual average rainfall during the

growing season. Fertilizer requirements for corn depend on

the type of soil, moisture availability, temperature in the

irrigated areas, and type of rotation. Corn is a relatively

heavy user of the major fertilizer elements and it is similar

to sorghum in total uptake (27). There are 7 groups of corn

based upon endosperm and glume characteristics. They are

dent (Zea mays indentata ), flint (Zea mays indurata), flour

(Zea mays amylacea), pop corn (Zea mays everta), sweet corn

(Zea mays saccharata), waxy iZ^^ mays), and pod corn (Zea

mays tunicata).

Corn is usually planted 5 to 7.5 cm deep. Like weeds,

insects are also a natural enemy of corn. Several insects

that can reduce corn production are European corn borer

miatraea grandiosella), chinch bug (BIJSSUS leucnpterns),

corn earworms (Heliothis zea) , corn root worms (Diabrnt-ica

nndecim punctata howardi) , grass hoppers (SJtQt.rQga

r^rpalella), weevils (Agrotis orthogonia), corn root aphid

(Aphis maidi radicis), larger corn-stalk borer (Diatraea

zeaCQlellfl), and seed corn maggot (Hylemyia platura).

Sorghum

Grain sorghum (Sorghum bicnlnr) belongs to the family

Gramineae, tribe Andropogoneae. Sorghum ranks fourth among

all the world cereal crops following wheat, rice and corn.

It is considered one of the five major crops in the world in

terms of acreage and world production. About 75% of the

total world production is in Asia and Africa where it is

utilized primarily as food. Sorghum is one of the most

important food crops in the dry areas of the world where

precipitation is very low and temperatures are very high.

Sorghum originated in east Africa, probably Ethiopia.

Sorghum is grown in warm areas or hot regions that have

adequate summer rainfall as well as in warm irrigated areas.

Sorghum is able to grow in those areas because this plant

has the ability to maximize its water use from the soil, has

extensive secondary root formation and smaller leaf area such

that more water is absorbed and less water lost, and has the

ability to grow on most types of soil.

The most favorable temperature for the growth of the plant

is about 37° C with an annual average rainfall of 42.5 to

62.5 cm. The plants remain practically dormant during

periods of drought but resume growth as soon as there is

7

sufficient rain to wet the soil. The fertilizer requirement

depends on the type of soil, moisture availability and

temperature (27). The crop has three defined growth stages.

One, from planting to emergence of the coleoptyle from the

soil; two, the stage from head initiation to blooming; and

three, the stage from flowering to physiological maturity.

Herbicides and Insecticides

Postemergence herbicides.used in this study were DPX-

V9360, CGA-136872, and DPX-79406. Much research has been

conducted using these sulfonylurea herbicides (5,14,15).

These three herbicides are in the sulfonylurea herbicide

class, which are absorbed rapidly by both foliage and roots

of susceptible plants. They are systemic herbicides, moving

in both the apoplast and symplast. The mechanism of action

of these herbicides is initiated by inhibiting cell division

in the shoot and root tip, and growth by inhibiting the plant

enzyme acetolactate synthase, thereby, blocking branched

chain amino acid biosynthesis. The effects are slow to

develop with the result being seen from one to three weeks

after treatment. The first symptom of activity is observed

in the meristematic tissues of treated plants. Sensitive

species quickly stop growing after application. Chlorosis,

necrosis, and death of plants follow this initial symptom in

sensitive grass and broadleaf species. Tolerant species

8

metabolize the sulfonylureas to non-herbicidal metabolites.

Broadleaf weeds are more susceptible than grasses.

Hydrolysis into non-herbicidal compounds is the major form of

degradation. This is followed by microbial breakdown of the

products of hydrolysis. The rate of hydrolysis is increased

by high soil moisture and low soil pH (12,16) .

DPX-V9360 or Accent [2-(((((4,6-Dimethoxypyrimidin-2-

yl)amino carbonyl))aminosulfonyl))-N,N-dimethyl-3-pyridine

carboxamide] is a new product from Dupont for selective

postemergence grass control in corn. To provide control of

several annual and perennial grasses with suppression of some

broadleaf weeds, requires 16-70 g/ha of DPX-V9360. DPX-V9360

has the ability to block cell division and growth via

inhibition of the plant enzyme acetolactate synthase (24,25).

Under a wide range of environmental conditions, DPX-V93 60

gives excellent selectivity on several corn varieties. An

adjuvant should be used with DPX-V9360. DPX-V9360 is more

effective on small actively growing grasses than on larger

grasses (24) .

Rotational crop tolerance to DPX-V9360 is excellent for

soybeans which are tolerant to the herbicide in neutral to

acid pH soils. DPX-V9360 is a herbicide that is safe for

corn. Reseach conducted to determine the tolerance of a

variety of corn to DPX-V9360 and to evaluate the efficacy of

the herbicide for quackgrass control revealed that DPX-V9360

did not injure the corn even at the highest rate (140 g/ha).

DPX-V9360 at 70 g/ha, applied postemergence, controlled 70%

of the quackgrass, while at the rate of 140 g/ha controlled

100% at 21 days after treatment (5).

CGA-136872, which has the trade name Beacon [3-(4,6-Bis-

(difluoromethoxy)-pyrimidin-2-yl)-1-(2-methoxy carbonyl

phenyl sulfonyl)urea], is a new postemergence corn herbicide

being developed by Ciba Geigy. Sorghum species are highly

sensitive to this compound. CGA-136872 has good activity

against several important dicotyledonous weeds. Plants take

this compound up through the foliage or through the root

system. The addition of a nonionic surfactant is needed in

the spray solution if it is to be taken up by the leaves.

Additive surfactants commonly used are crop oil concentrate

(COC), X-77 and 28% N. CGA-136872 is rapidly absorbed and is

efficiently translocated within the phloem and xylem to the

actively growing meristematic tissues of the foliage and

root. The rate for acceptable weed control ranges from 5-40

g/ha depending on species, timing, and environmental

conditions (23,33). CGA-136872 is less phytotoxic when

applied to the soil than when applied to the foliage (23).

Other herbicides may be used to increase the spectrum of

control. Field studies with CGA-136872 at the rate of 40

g/ha gave the results of 56.4% and 30.8% injury on a

sensitive variety of corn with and without terbufos,

10

respectively. A tolerant variety provided 18.0% and 6.0%

injury with and without terbufos, respectively (24). In all

cases, both tolerant and susceptible, corn treated at

planting with terbufos and 2 weeks after planting treated

with CGA-136872 was injured significantly more than the corn

that did not receive the insecticide treatment. The

insecticide alone did not cause phytotoxic symptoms. CGA-

136872 at 20 g/ha applied postemergence provided acceptable

control of susceptible weed species. When the rate was

increased to 40 g/ha, weed control increased only about 5 to

10% (14,23) .

Another herbicide that was used in this study was DPX-

79406. It is a premix of two sulfonylurea herbicides; a 1:1

mixture of DPX-V9360 and DPX-E9636. The herbicidal

activities of the two compounds are additive. This compound

is a new postemergence herbicide for corn in areas with high

soil pH and sensitive rotational crops. It controls a broad

spectrum of annual and perennial grass weeds and some broad

leaf weeds at rates from 15 to 50 g/ha. This mixture is more

active, controls a broader weed spectrum and gives greater

rotational crop flexibility than DPX-V9360 alone (15).

Application of a herbicide mixture usually results in more

control of weeds than if a single herbicide is applied.

Studies of DPX-V9360 with 2,4-D and dicamba were conducted to

control hemp dogbane (Apocynum cannabinum) and wild

11

blackberry (Rubus allegheniensis) in no-till corn. The

results showed only 75% to 80% control of 25-cm high hemp

dogbane and 68% to 80% control of 38-cm high wild blackberry

with DPX-V9360. The control from 2,4-D and dicamba were 50%

and 70%, respectively, of hemp dogbane and 23% and 50%,

respectively, of wild blackberry. However, the results for

the combined herbicides, 70 g/ha DPX-V9360 plus 1% soybean

oil as an adjuvant and 0.6 kg/ha 2,4-D, were 97% hemp dogbane

control and 85% wild blackberry control 10 weeks after

application (19). Studies conducted by Witt and Charles (48)

in 1988 showed no corn injury with a combination of DPX-V9360

and CGA-136872 with Carbofuran. A combination of these two

herbicides with Chlorpyrifos, Fonofos, Tefluthrin or Terbufos

resulted in greater corn injury than with the herbicides

applied alone (48).

A study conducted in Arlington, Wisconsin showed that

multiple applications of reduced rates of DPX-V93 60 provided

better foxtail control than single applications at higher

rates (28). Late postemergence application of DPX-V9360,

CGA-136872 and DPX-79406 on quackgrass (Agropyron repens (L.)

Beauv.) were more effective than early postemergence (50).

Herbicide-insecticide mixtures are commonly used in modern

pest management situations. The interactions of these two

categories of pesticides, both synergistic and antagonistic

have been reported by a number of researchers (18,41,45) .

12

The insecticides used in this study were Counter, Furadan,

and Lorsban. Counter or terbufos [S-(((1,1-dimethylethyl)

thio)methyl)0,0-diethyl] is an insecticide that is commonly

used in control of billbugs, corn rootworms, nematodes, seed

corn beetle, seed corn maggots, and wireworms. It is a

systemic insecticide, used in field corn, popcorn, sweet

corn, sugar beets and grain sorghum (35).

The second insecticide used was Furadan or carbofuran

[2, 3-Dihydro-2,2 dimethyl-2-7-N-benzofuranyl methyl

carbamate] which is a systemic carbamate insecticide.

Furadan is compatible with all non alkaline pesticides and

fertilizers (38). The carbamates are derivatives of carbamic

acid. Like organophosphates, the mode of action of

carbamates is that of inhibiting the vital enzyme

cholinesterase. The first successful carbamates were

introduced in 1956. Two distinct qualities have made it the

most popular material: very low mammalian oral and dermal

toxicity and a rather broad spectrum of insect control (46).

Furadan is effective against soil insects in corn, cotton,

and pests on potatoes.

The third insecticide used in this study was Lorsban.

Lorsban or chlorpyrifos [0,0-diethyl 0-(3,5,6-trichloro-2-

pyridyl) phposphorothioate] is a residual organophosphate

insecticide which has been effective for controlling

mosquitoes, insects in field crops and household pests. It

13

is a stomach and contact poison with a long residual life in

the soil and a short one on foliage (29,36)

Several studies have been conducted to investigate

insecticide interactions with sulfonylurea herbicides

(43,45,48). A study using terbufos (Counter), Chlorpyrifos

(Lorsban) and Fonofos with DPX-V9360 was conducted in 1988.

DPX-V9360 applied to corn treated with Terbufos or Fonofos

resulted in more corn injury than DPX-V9360 applied to corn

treated with Chlorpyrifos (43).

CHAPTER III

MATERIALS AND METHODS

Two studies, greenhouse and field, were designed to

evaluate the main effects and the interactions between

herbicides and insecticides applied to three corn hybrids .

These studies were established in the Agronomy, Horticulture,

and Entomology Department greenhouse located at Texas Tech

University and at the Texas Agricultural Experiment Station,

Lubbock, Texas. The experiments were conducted during the

Fall, Spring and Summer of 1989-1990.

Hybrids

Three corn (Zea mays L.) hybrids (Dekalb 711, Pioneer

3168, and Triumph 2020) were used in these studies. Sorghum

(Sorghum bicolor) seeds (Dekalb DK 46) for the residue study

were supplied by the Texas Agricultural Experiment Station,

Lubbock, Texas.

nrP^pnhouse Studv

The soil type was an Amarillo sandy clay loam which has a

pH 6,6 to 7.8 and organic matter less than 1%. The soil was

secured from an area that has not recently received a

herbicide or insecticide application. One hundred and forty-

four 8-liter pots were filled with the soil. The soil was

14

15

fertilized by using Zipp (16-8-8) at the rate of 0.9 g/pot

(equivalent to 18, 9, and 9 kg/ha of N, P2O5, and K2O) and

watered to bring the soil to field capacity.

Four blocks of a randomized complete block design with a

factorial arrangement of treatments were used for this study.

Herbicides, insecticides, and hybrids were the treatments.

All of the treatments were randomly assigned within each

block. Each block consisted of 36 treatments.

Three corn hybrids were planted on January 2 6, 1990 at the

rate of four seeds per pot. Seedlings emerged within 5 to 6

days and good survival of the corn was observed in all of the

pots. The plants were thinned to 2 plants per pot on

February 12.

The insecticides, Furadan, Lorsban, and Counter, were

applied at planting at a rate of 1.1 kg a.i./ha (3.7 mg

a.i./pot or 24 mg product/pot). The insecticide application

was made in the middle of the pot adjacent to the seeds. In

addition, an untreated control with no insecticide

application was established (Table 1) .

The herbicides, DPX-V9360 and CGA-136872, were applied

post emergence over the top of the 15 cm tall corn plants at

the label rate four weeks after planting. The application

was made by using CO2 sprayer at a pressure of 0.2 mPa. The

sprayer was calibrated to apply 140 1/ha of water. Also, an

untreated control with no herbicide application was

16

Table 1. Insecticides, application rates, and time of application for the greenhouse and field studies.

Treatment No

Insecticide

Common name

Trade name

Rates Application (kg ai/ha)

1

2

3

4

Carbofuran Furadan

Chlorpyrifos Lorsban

Terbufos Counter

Untreated control

1.1

1.1

1.1

at planting

at planting

at planting

17

established (Table 2). Corn height measurements were begun

four weeks after planting and continued every two weeks until

harvest. Visual injury ratings were collected two weeks

after the herbicides were sprayed. Visual injury ratings

were made by comparing treated to untreated pots and

assigning 0 to no crop injury and 10 as complete crop kill.

Corn plants were harvested 10 weeks after planting. All

plants were used for wet and dry weight determinations for

each treatment. Wet weights were recorded and then the

plants were dried in an oven at 70° C for 12 days until the

weight did not change to obtain the dry weights.

Sorghum was planted 2 weeks after harvesting the corn

plants using the same soil to note any residual effect of the

herbicides and insecticides. This was done by visual

observations of plant coloring to check for chlorosis and by

actual stand counts to see if stand reductions resulted.

Sorghum visual injury ratings were made four weeks after

planting using the same visual ratings described above.

The data were analyzed according to the methods for analysis

of variance set forth by Steel and Torrie (1980) and Gomez

and Gomez (1984). Duncan's "New Multiple Range Technique"

was used to evaluate differences among treatment means. In

Table 3 the sources of variation and degrees of freedom for

the ANOVA are depicted.

18

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T3 <D 4-) fd (L)

4-) G D

CNJ 00 ^ LO vo r~

> -o p

4-) CO

0) CO P o

j i :

c <u <u M Cn

Q) Xi 4-J

c - H

T3 <D CO P

CD M 0) 5 r-

-o C fd

^ LO

V

00

CO 4-» G <D

a 4-> fd <D U

4-)

> i rH

G o

en G

- H 4-> G (d

r-i

a M 0) 4J 4-1 fd

CO M <D <D ^

II

CM < [2

CM

19

Table 3. Sources of variation and degrees of freedom for the analysis of variance for the greenhouse study.

Source of Variation df

Block (B) (b-1) 3

Hybrid (Hy) (hy-1) 2

Insecticide (I) (i-1) 3

Herbicide (H) (h-1) 2

Hy X I (hy-1)(i-1) 6

Hy X H (hy-1)(h-1) 4

I X H (i-1) (h-1) 6

Hy X I X H (hy-1) (i-1) (h-1) 12

Error (b-1)(hyih-1) 105

Total (bhyih-1) 143

20

Field Study

The field investigation area was located at the Texas

Agricultural Experiment Station, Lubbock, Texas. The soil in

the test area was an Amarillo Sandy clay loam containing less

than 1% organic matter.

The field study consisted of testing the effects of

herbicides, insecticides, and their interrelationships on

three hybrids of corn. Each hybrid of corn represented a

different study; therefore, three field studies were

established. Each field study was a split plot design with

three blocks. The main plots were the seven herbicide

treatments (Table 2) and the sub-plots were the four

insecticide treatments (Table 1). The herbicide treatments

were randomized within each of the blocks; however, the

insecticide treatments were fixed. The plots consisted of 8

rows (1.0 meter row spacing) that were 3 meters long

Three corn hybrids (Dekalb 711, Pioneer 3168, and Triumph

2020) were planted on May 17, 1990, at the rate of 160,550

seeds per hectare. The planting was done with a four-row

John Deere Max-Emerge planter. Good emergence and survival

of the corn was observed in all of the plots. Insecticides

were applied using chain-driver boxes attached to the

planter.

Three sulfonylurea herbicides (at two rates each) were

applied post emergence over the top of the corn (Table 2).

21

Application of herbicides was made when the corn plants had 4

to 6 leaves, four weeks after planting. All herbicide

treatments included a non-ionic surfactant at 0.25% v/v were

applied using a CO2 sprayer with 8002 nozzles at a pressure

of 0.2 mPa and a speed of 1.3 meters per second.

The test area was bedded before planting. The test area

was irrigated with well water to bring the soil moisture to

field capacity to provide moisture for germination of the

corn. Irrigation water was applied at the rate of 0.03

hectare-meters on May 22, 1990. Also, rainfall was received

periodically during the growing season. The second and third

irrigations were applied at the rate of 0.02 hectare-meters

on June 18, and July 9, 1990. Preplant fertilizers used in

this study were 134 kg/ha of nitrogen and 45 kg/ha P2O5.

Propazine at 1.1 kg/ha ai was applied as a preemergence

herbicide for broadleaf weed control.

The corn test area received two cultivations. The first

cultivation was made on June 8 and another cultivation was

done on June 2 8 to form water furrows.

The corn height measurements were begun at spraying, four

weeks after planting, and continued every two weeks for a

total of four plant height measurements. At the same time,

stand counts of the crop were made by determining the number

of plants per square meter in each plot. Visual injury

ratings of corn were established two weeks after spraying of

22

herbicides by comparing treated to untreated plots and

assigning 0 to no crop injury and 10 as complete crop kill.

The data were analyzed according to the methods for

analysis of variance set forth by Steel and Torrie (1980) and

Gomez and Gomez (1984). In Table 4 the sources of variation

and degrees of freedom for the ANOVA are depicted.

23

Table 4. Sources of variation and degrees of freedom for the analysis of variance of each corn hybrid in the field study.

Source of variation df

Block (B) (b-1) 2

Herbicide (H) (h-1) 6

Error (a) (b-1)(h-1) 12

Insecticide (I) (i-1) 3

H X I (h-1)(i-1) 18

Error (b) h(b-l) (i-1) 42

Total (bhi-1) 83

CHAPTER IV

RESULTS AND DISCUSSION

Greenhouse Study

Wet Weight

The analysis of variance for wet weight is given in

Appendix A, Table Al. Among primary effects, only hybrid and

herbicide were statistically significant.

Hybrid Effect

Hybrid effects are shown in Table 5. The hybrid means

indicated that Dekalb 711 resulted in 84.6 grams of wet

weight and was significantly different from Pioneer 3168

(75.7 grams) and Triumph 2020 (79.4 grams). However, Pioneer

3168 was not significantly different from Triumph 2020.

Herbicide Effect

Overall herbicide mean data showed that there were no

significant differences between the control and DPX-V9360,

but they were both significantly different from CGA-136872

(Table 5). The untreated control (83.0 grams) and DPX-V9360

(82.0 grams) had higher wet weights than CGA-136872 (74.7

grams). Therefore, it appears that CGA-136872 had a

detrimental effect on the growth (wet weight) of the corn

hybrids.

24

25

Table 5. Effect of hybrid and herbicide on corn wet weight at harvest (averaged over all insecticide means) for the greenhouse study.

Herbicide Hybrid

Dekalb 711 Pioneer 3168 Triumph 2020 Mean

grams

Control

DPX-V93 60

CGA-136872

88.8

86.9

78.1

79.3

78.5

69.3

80.8

80.6

76.7

83.0a

82 .Oa

74 .7b

Mean- 84. 6A 75.7B 79.4B 79.9

^ Means in the same column followed by the same small letter are not significantly different at the 5% level of probability according to Duncan's Test.

2 Means in the same row followed by the same capital letter are not significantly different at the 5% level of probability according to Duncan's Test.

26

Insecticide Fff^nt

No significant effects on the wet weight of corn due to

application of insecticides were noted (Appendix A, Table

Al) . This study would indicate that these insecticides,

Lorsban, Furadan and Counter, did not have any adverse

effects on the crop.

Interaction F.ffprt-

The interactions of hybrid X insecticide X herbicide, hybrid

X insecticide, hybrid X herbicide, and insecticide X

herbicide on corn wet weights were not significantly

different (Appendix A, Table Al). These data indicated no

beneficial or adverse effects on the wet weights from these

treatment interactions (Appendix A, Table A2).

Dry Weight

The analysis of variance for corn dry weight is presented

in Appendix B, Table Bl. Among primary effects, only

herbicide was statistically significant. No significant

differences were observed for insecticide, hybrid and the

interactions of hybrid X insecticide, hybrid X herbicide,

insecticide X herbicide, and hybrid X insecticide X

herbicide.

27

Hybrid Fffert-

Hybrid effects are shown in Table 6. The hybrid means

indicated that among Dekalb 711, Pioneer 3168 and Triumph

2020 no significantly different effects were noted on corn

dry weights. Therefore, all hybrids responded similarly.

Insecticide Effect

The effect of insecticide treatments did not show any

significant differences on corn dry weight (Appendix B,

Table Bl). Therefore, no differential response to the

insecticides was observed.

Herbicide Effect

The overall mean data of herbicide effect on corn dry

weight are given in Table 6. No significant differences were

observed between the control and DPX-V9360 (8.9 and 8.5

grams, respectively); however, they both had a greater dry

weight than CGA-136872 (7.1 grams). Therefore, CGA-136872

had a detrimental effect on the dry matter accumulation of

these corn hybrids.

Interaction Effect

The interactions of hybrid X insecticide X herbicide,

hybrid X insecticide, hybrid X herbicide, and insecticide X

herbicide for corn dry weights were not significantly

28

Table 6. Effect of hybrid and herbicide on corn dry weights (averaged over all insecticide means) for the greenhouse study.

Hybrid

Herbicide Dekalb 711 Pioneer 3168 Triumph 2020

grams

Mean-

Control 9.2

DPX-V9360 8.8

CGA-136872 7.2

8.7

8.5

6.8

8 . 8

8 . 3

7 . 2

8 . 9 a

8 . 5 a

7 . 1 b

Me an 2 8.4A 8.0A 8.1A 8.2

1 Means in the same column followed by the same small letter are not significantly different at the 5% level of probability according to Duncan's Test.


29

different (Appendix B, Table Bl). These data indicated no

negative or positive effects on the dry weights from these

interactions (Appendix B, Table B2).

Corn Height

The corn height results indicated significant differences

due to hybrids when measured at 4, 6, and 8 weeks after

planting (Appendix C, D, E, Tables CI, Dl, and El) and

herbicides at 6 and 8 weeks after planting. Data for the

main effects and interactions may be noted in Appendix Tables

C2, D2, and E2.

Hybrid Effect

The effects of hybrid on corn height was significant when

measured at 4, 6, and 8 weeks after planting (Tables 7, 8,

and 9, respectively). At 4 weeks after planting. Pioneer

3168 had the greatest plant height (39.1 cm) followed by

Triumph 2020 (35.5 cm) and Dekalb 711 (34.3 cm) (Table 7).

At 6 weeks after planting, the same trend was observed with

again Pioneer 3168 having the greatest plant height (58.1 cm)

followed by Triumph 2020 (52.0 cm) and Dekalb 711 (49.9 cm).

At 8 weeks after planting. Pioneer 3168 had also the greatest

plant height (7 9.2 cm) followed by Triumph 2020 (71.6 cm) and

Dekalb 711 (68.4 cm). These data indicate that hybrid

30

Table 7. Effect of hybrid and herbicide on corn height when measured 4 weeks after planting (averaged over all insecticide means) for the greenhouse study.

Hybrid

Herbicide Dekalb 711 Pioneer 3168 Triumph 2020 Mean^

cm

Control 34.9 39.5 35.2 36.5a

DPX-V9360 34.1 39.1 35.4 36.2a

CGA-136872 33.8 38.8 35.9 36.2a

Mean2 34.3A 39.IB 35.5C 36.3



31


Hybrid

Herbicide Dekalb 711 Pioneer 3168 Triumph 2020 Mean-

cm

Control 52.0 59.0 52.6 54.5a

DPX-V9360 51.3 59.4 52.6 54.4a

CGA-136872 46.4 55.8 50.7 51.0b

Mean2 49.9A 58.IB 52.OC 53.3



32


Hybrid


cm

Control 74.8 83.1 74.7 77.5a

DPX-V9360 70.7 82.1 73.5 75.5a

CGA-136872 59.7 72.3 66.5 66.2b

Mean2 68.4A 79.2B 71.6C 73.0



33

selection did have an effect on the plant height measurements

4, 6, and 8 weeks after planting.

Insecticide Fffpr-t

The insecticide effects on corn height averaged over

hybrids and herbicides showed no differences at any of the

dates. Therefore, it was concluded that these insecticides

have no differential effects on corn height through 8 weeks

after planting.

Herbicide Effect

With respect to corn height, herbicide differences were

noted when measured at 6 and 8 weeks after planting (Tables 8

and 9, respectively). When measured at 6 and 8 weeks after

planting (2 and 4 weeks after spraying), CGA-136872 had the

greatest effect on reducing corn height. CGA-136872 at 6 and

8 weeks after planting resulted in a significantly lower corn

height (51.0 and 66.2 cm, respectively) than did the control

(54.5 and 77.5 cm, respectively) and DPX-V9360 (54.4 and

75.5 cm, respectively) (Tables 8 and 9). No differences

between the control and DPX-V9360 were observed at either 6

or 8 weeks after planting. These data suggest that CGA-

136872 had a detrimental effect on corn growth, as measured

by the plant heights at 6 and 8 weeks after planting (2 and 4

weeks after spraying).

34

Interaction Fffprt

The data for the interactions of hybrid X insecticide X

herbicide, hybrid X insecticide, hybrid X herbicide, and

insecticide X herbicide on corn heights at 4 weeks after

planting (measured when spraying herbicide) are shown in

Appendix C, Table C2. The data for these interactions on

corn heights at 6 weeks after planting (measured 2 weeks

afrer spraying) are shown in Appendix D, Table D2. The data

for corn heights at 8 weeks after planting (measured 4 weeks

after spraying of the herbicides) are shown in Appendix E,

Table E2. All of these interactions were non significant,

thus, indicating no interaction effects on corn heights for

these hybrids when measured 4, 6, and 8 weeks after planting.

Sorghum Injury

Sorghum injury results showed statistically significant

differences only for the herbicide treatments (Appendix F,

Table Fl) .

Hybrid Effect

There were no significant differences among hybrids on

sorghum injury when averaged across insecticide and herbicide

treatments (Appendix F, Table Fl). This indicated that these

35

hybrids had no adverse effect on the subsequent growth of

sorghum.

Insecticide Fffpr-t

No significant differences were observed among

insecticides as to their effect on sorghum injury after

treating corn (Appendix F, Table Fl). The differences

between treatment means on sorghum injury were very small

(Appendix F, Table F2). These results would indicate that

these insecticides are safe for sorghum rotation after corn

under the conditions of this study.

Herbicide Effect

Herbicide effects, when averaged across insecticides and

hybrids, were significantly different (Table 10). DPX-V9360

resulted in a significant higher sorghum injury rating (8.0)

than did CGA-136872 (0.1) and the control (0.1) . However, no

differences were noted between CGA-136872 and the control

(0.1 and 0.1, respectively). This indicates that DPX-V9360

persists in the soil and can cause injury to the next

rotational crops, especially sorghum.

Tnl-praction Effect

No significant differences on sorghum injury were observed

in the analysis of variance due to interaction of these

36

Table 10. Effect of hybrid and herbicide on sorghum injury (averaged over all insecticide means) in the greenhouse.

Hybrid


o, o

Control 1.0 1.0 1.0 1.0a

DPX-V9360 82.0 79.0 80.0 80.0b

CGA-136872 0.0 2.0 0.0 1.0a


37

treatments (Appendix F, Table Fl). Therefore, no

differential effects of these interactions were of any

importance (Appendix F, Table F2).

Field Stiidy

Plants per Square Meter for Dekalb 711

The analysis of variance for the number of plants per

square meter is given in Appendix G, Table Gl. The only

treatment that was significant was that of insecticides. The

main effect of herbicide and the herbicide X insecticide

interaction were not significant.

Insecticide Effect

Overall plants per square meter mean data showed that

there were significant differences between the three

insecticides and the control; however, the three insecticides

were not different each other (Table 11). In this table, the

control had a lower plants per square meter (9.6) than did

Counter, Furadan, and Lorsban (11.8, 11.4, and 11.2,

respectively). This would indicate that the three

insecticide treatments gave sufficient control of soil

insects such that corn plant establishment was enhanced over

that of no insecticide application.

38

Table 11. Effect of herbicide and insecticide on the number of plants per square meter of Dekalb 711 in the field study.

Insecticide

Herbicide Furadan Lorsban Control Counter Mean^

#/m2

DPX-79406,26 10.3 10.3 8.6 11.0 10.0a

DPX-79406,35 13.3

DPX-V9360,35 12.3

DPX-V9360,53 11.3

CGA-136872,33 10.6

CGA-136872,40 11.0

Control 10.6

Mean2 11.4A 11.2A 9.6B 11.8A 11.0



1 0 . 3

1 0 . 6

1 1 . 3

1 2 . 0

1 2 . 0

1 2 . 0

1 0 . 3

1 1 . 0

9.0

8 .0

1 0 . 3

10 .0

1 2 . 0

1 1 . 0

1 1 . 6

1 2 . 0

1 0 . 3

1 4 . 6

1 1 . 5 a

1 1 . 2 a

1 0 . 8 a

1 0 . 6 a

1 0 . 9 a

1 1 . 8 a

39

Herbicide Effect

The data of plants per square meter for herbicide

treatments when averaged across insecticides, are given in

Table 11. The effects of herbicides were not significantly

different, due to the ratings and spraying were made on the

same day.

Interaction Effect

The insecticide X herbicide interaction was not

significantly different on the number of plants per square

meter (Appendix G, Table Gl). The mean data are presented in

Table 10. These data indicate that no negative or positive

effects of interaction between herbicide and insecticide.

Corn Height for Dekalb 711

The analyses of variance for corn heights are presented in

Appendix H, Tables HI, H2 and H3. Among primary effects

only, the insecticide treatments were significant.

Insecticide Effect

The corn plots treated with the insecticide Counter had

significantly greater plant heights than those treated with

Furadan, Lorsban, and the control when measured 4 weeks after

planting (Table 12) . However, Furadan, Lorsban, and the

control were not significantly different from each other. At

40

Table 12. Effect of herbicide and insecticide on corn heights when measured 4 weeks after planting of Dekalb 711 in the field study.

Herbicide

DPX-79406,26

DPX-79406,35

DPX-V9360,35

DPX-V9360,53

36.7

38.3

36.7

36.7

CGA-136872,33 33.3

CGA-136872,40 35.8

Insecti CJHP

Furadan Lorsban Control Counter Mean^

Control 35.0

3 5 . 8

3 1 . 7

3 5 . 8

3 6 . 7

3 5 . 0

3 1 . 7

3 3 . 3

cm

3 4 . 2

3 5 . 8

3 5 . 8

4 0 . 0

3 4 . 2

3 5 . 8

3 7 . 5

35.8

40.0

37.5

40.0

38.3

35.8

42.5

35 . 6a

36.4a

37.4a

38.3a

35 . 2a

34.8a

37.0a

Mean^ 3 6.0A 34 .3A 36.2A 38.6B 36.3



41

6 weeks after planting no significant differences between the

control and Counter on corn height was observed; however,

both resulted in greater plant heights than those treated

with Furadan or Lorsban (Table 13). At 8 weeks after

planting, plots treated with Counter and Furadan resulted in

shorter plants while no detrimental effects was noted for

Lorsban (Table 14). These data suggested some detrimental

effects of Furadan on corn growth when measured 6 and 8 weeks

after planting.

Herbicide Effect

The herbicide effects were not significantly different on

corn heights when measured 4, 6, and 8 weeks after planting

(Appendix H, Tables HI, H2, and H3). These data indicate no

detrimental effects on corn heights from herbicide

treatments.

Interaction Effect

Appendix H, Tables HI, H2 and H3 also showed no

significant interaction effects between insecticide and

herbicide treatments on corn heights at any of the dates.

Therefore, this would indicate that no detrimental effects of

these materials on corn heights measured 4, 6, and 8 weeks

after planting.

42

Table 13. Effect of herbicide and insecticide on corn height when measured 6 weeks after planting of Dekalb 711 in the field study.

Herbicide

Insecticide

Furadan Lorsban Control Counter Mean-

cm

DPX-79406,26 94.2

DPX-79406,35 92.5

DPX-V9360,35 94.2

DPX-V9360,53 95.0

CGA-136872,33 87.5

CGA-136872,40 93.3

Control 95.0

90.0

89.2

91.7

94.2

92.5

90.8

94.2

96.7

97.5

96.7

100.8

95.0

91.7

99.2

9 5 . 0

9 5 . 0

9 6 . 7

9 7 . 5

9 5 . 8

8 8 . 3

9 5 . 0

9 3 . 9 a

9 3 . 5 a

9 4 . 8 a

9 6 . 9 a

9 2 . 7 a

9 1 . 0 a

9 5 . 8 a

Mean^ 93. lA 91. 8A 96.8B 94. 8B 94.1



43

Table 14. Effect of herbicide and insecticide on corn heights when measured 8 weeks after planting of Dekalb 711 in the field study.

Herbicide

DPX-79406,26

DPX-79406,35

DPX-V9360,35

DPX-V9360,53

CGA-136872, 33

CGA-136872,40

Control

Me an 2

Furadan

159.2

160.0

163.3

153.3

140.0

153.3

155.0

154.9A

"'"n-'SeCt i r̂ i d p

Lorsban

163.3

164.2

160.8

164.2

159.2

157.5

162.5

161.7B

Control

cm

161.7

164.2

160.0

161.7

165.0

164.2

165.0

163.IB

Counter

142.5

145.8

144.2

146.7

151.7

155.0

160.0

149.4C

Mean^

156.7a

158.5a

157.0a

156.4a

153.9a

157.0a

160.6a

157.2



44

Plants per Square Meter for Pioneer 3168

The analysis of variance for number of plants per square

meter is presented in Appendix I, Table II. Among the

primary effects, only the insecticide treatments were

significantly different.

Insecticide Effect

The data for the number of plants per square meter are

given in Table 15. The effects of Furadan, Lorsban and the

control were not significantly different, but the effects of

these three treatments were different from Counter. Counter

had the greatest number of plants per square meter (14.1)

followed by Furadan (12.2), Lorsban (11.9) and the control

(10.9). These data indicate that Counter had a beneficial

effect on stand establishment.

Herbicide Effect

There were no significant differences due to herbicides on

the number of plants per square meter (Appendix I, Table II).

Therefore, no differential response to the herbicides was

observed.

Interaction Effect

The data for interaction between insecticide and herbicide

are presented in Table 15. No significant differences were

45

Table 15. Effect of herbicide and insecticide on the number of plants per square meter of Pioneer 3168 in the field study.

Herbicide

Insecticide


#/m̂

DPX-79406,26 12.0 11.0 11.6 12.3 11.7a

DPX-79406,35 12.6

DPX-V9360,35 12.6

DPX-V9360,53 12.0

CGA-136872,33 13.6

CGA-136872,40 11.0

Control 11.6

13.3

11.6

14.3

11.3

10.3

11.3

11.0

10.6

11.6

11. 6

9.6

10.3

15.0

15.3

13.3

14.0

13.3

15.3

13.0a

12.5a

12.8a

12. 6a

11.1a

11.1a

Mean^ 12.2A 11. 9A 10. 9A 14.1 12.3



46

observed for the means. These data suggest that no adverse

effects on the number of plants per squre meter from these

treatment interactions existed.

Corn Height for Pioneer 3168

The corn height data for Pioneer 3168 indicated

statistically significant differences for the main effect of

insecticide. No significant differences were observed for

herbicides or the interaction of insecticide X herbicide

(Appendix J, Table Jl, J2, J3) .

Insecticide Effect

There were significant differences among insecticide

treatments on corn heights measured 4, 6, and 8 weeks after

planting when averaged across herbicide treatments (Tables

16, 17, and 18, respectively). At 4 weeks after planting,

the Furadan and Lorsban effects were not different from the

control (30.6, 30.3, and 32.4 cm, respectively), however,

plant heights were greater from plots treated with Counter

(34.7 cm)(Table 16). The corn height measured 6 weeks after

planting indicated that there were no significant differences

between the control and Counter treated plots (96.4 and

97.0 cm), but they both were significant greater than those

treated with Furadan and Lorsban (94.0 and 91.6 cm,

respectively)(Table 17). The effects of insecticides on corn

47

Table 16. Effect of herbicide and insecticide on corn heights when measured 4 weeks after planting of Pioneer 3168 in the field study.

Insecticidp


cm

DPX-79406,26 27.5 28.3 35.0 31.7 30.6a

DPX-79406,35 30.0 30.0 29.2 35.0 31.0a

DPX-V9360,35 31.7 26.7 31.7 35.8 31.4a

DPX-V9360,53 30.0 31.7 34.2 35.0 32.7a

CGA-136872,35 34.2 29.2 35.0 35.0 33.3a

CGA-136872,40 31.7 33.3 30.0 35.0 32.5a

Control 29.2 33.3 31.7 35.8 32.5a

Mean2 30.6A 30.3A 32.4A 34.7B 32.0



48


Herbicide

Insecticide


cm

DPX-79406,26 87.5

DPX-79406,35 94.2

DPX-V9360,35 90.8

DPX-V9360,53 93.3

CGA-136872,33 97.5

CGA-136872,40 95.8

Control 99.2

84.2

90.8

86.7

92.5

92.5

95.0

99.2

96.7

99.2

95.0

97.5

99.2

101.7

103.3

95.0

98.3

95.0

95.8

97.5

100.0

97.5

90.8a

95.6a

91.9a

94.8a

96.7a

98.1a

99.8a

Mean^ 94. OA 91. 6A 96.4B 97. OB 95.4

^ Means in the same column followed by the same letter are not significantly different at the 5% level of probability according to Duncan's Test


49

height measured 8 weeks after planting are depicted in

Table 18. This data indicated no significant differences

among the control, Lorsban and Counter treated plots (145.2,

142.6, and 142.2 cm, respectively), but they were

significantly greater than the Furadan treated plots (135.7

cm) . While these data were somewhat eratic, it appears that

Furadan had somewhat of a phytotoxic effect on corn under the

conditions of this study.

Herbicide Effects

The overall corn height mean measured 4, 6, and 8 weeks

after planting averaged over insecticide treatments are given

in Tables 16, 17, and 18. No significant differences were

observed among the herbicide treatments. This indicated that

no differential effects of herbicides on corn heights

measured through 8 weeks after planting were evident.

Interaction Effect

The interaction of insecticide X herbicide was not

statistically significant for corn height (Appendix J, Tables

Jl, J2, J3). These data show no beneficial or adverse

effects of these treatment interactions on corn heights

through 8 weeks after planting.

50


Insecticide


cm

DPX-79406,26 142.5 141.7 141.7 144.2 142.5a

DPX-79406,35 138.3 149.2 149.2 147.5 146.0a

DPX-V9360,35 130.8 140.0 137.5 140.8 137.3a

DPX-V9360,53 130.8 141.7 151.7 145.0 142.3a

CGA-136872,33 135.8 141.7 139.2 133.3 137.5a

CGA-136872,40 135.0 140.0 150.0 145.8 142.7a

Control 136.7 144.2 147.5 138.3 141.7a

Mean2 135.7A 142.6B 145.2B 142.2B 141.4



51

Plants per Square Meter for Triumph 2020

The analysis of variance for corn plants per square meter

is given in Appendix K, Table Kl. The only treatment that

was significant was that of insecticides. Other treatments,

herbicide, and the interaction of insecticide X herbicide

were not statistically significant.

Insecticide Effect

There were no significant differences among the three

insecticide treatments. Counter, Lorsban and Furadan;

however, they all resulted in a higher stand establishment

than the control (Table 19). The control had the lowest

plants per square meter (8.3) and Counter resulted in the

highest plants per square meter (10.3) . This suggested that

insecticide treatments gave better results of plants counts

than the control.

Herbicide Effect

According to the analysis of variance, the number of

plants per square meter, averaged over insecticide

treatments, was not different for the herbicide treatments

(Table 19). This indicated that herbicides had no negative

effects on the number of plants per square meter.

52

Table 19. Effect of herbicide and insecticide on the number of plants per square meter of Triumph 2020 in the field study.

Herbicide

Insecticide


#/m2

DPX-79406,26

DPX-79406,35

DPX-V9360,35

DPX-V9360,53

9.6

9.3

9.6

9.6

CGA-136872,33 9.6

CGA-136872,40 12.0

Control 8.0

8 . 0

8 . 6

1 0 . 6

1 1 . 0

9 . 0

1 1 . 3

9 . 6

1 0 . 6

8 . 6

7 . 6

8 . 3

8 . 3

7 . 3

7 . 3

1 1 . 3

1 0 . 0

1 0 . 6

1 1 . 3

1 0 . 6

9 . 0

9 . 3

9 . 9 a

9 . 2 a

9 . 6 a

1 0 . 1 a

9 . 4 a

9 . 9 a

8 . 6a

Me an 2 9.7A 9.7A 8.3B 10. 3A 9.5



53

Interaction Effprt

The interaction of insecticide X herbicide was not

significantly different (Appendix K, Table Kl). These data

suggest that no negative or positive effects of insecticide

and herbicide interactions on the growth of Pioneer 3168

hybrid existed.

Corn Height for Triumph 2020

The corn height results indicated statistically

significant differences only for the main effect of

insecticide treatments (Appendix L, Tables LI, L2, L3).

Insecticide Effect

The effects of insecticides on corn heights were

significant when measured at 4, 6, and 8 weeks after planting

(Tables 20, 21, and 22). At 4 weeks after planting, plants

treated with Counter had the greatest plant height (27.4 cm)

followed by Furadan (26.3 cm), control (24.2 cm) and Lorsban

(21.7 cm)(Table 20). At 6 weeks after planting (Table 21),

the same general trend was observed with Counter and Furadan

treated plots having the greatest corn height (93.8 and 93.0

cm, respectively) followed by the control (89.2 cm) and

Lorsban (85.5 cm). At 8 weeks after planting (Table 22), the

control had the greatest corn height (168.0 cm) followed by

Lorsban (161.3 cm). Counter (157.2 cm) and Furadan

54

Table 20. Effect of herbicide and insecticide on corn heights measured 4 weeks after planting of Triumph 2020 in the field study.

Herbicide

DPX-79406,26

DPX-79406,35

DPX-V9360,35

DPX-V9360,53

CGA-136872,33

CGA-136872,40

Control

Mean^

Furadan

21.7

25.8

28.3

27.5

26.7

28.3

25.8

2 6. 3 A

Tnser't

Lorsban

20.0

22.4

23.3

19.2

24.2

20.0

22.5

21.7B

icide

Control

cm

25.0

25.0

27.5

22.5

22.5

23.3

23.3

24.2C

Counter

27.5

25.8

30.8

26.7

29.2

26.7

25.0

27.4A

Mean^

23.5a

24.8a

27.5a

23.9a

25.6a

24.6a

24.2a

24.9


2 Means in the same row followed by the same capital letter are not significantly different at the 5 % level of probability according to Duncan's Test.

55


Herbicide

DPX-79406,26

DPX-79406,35

DPX-V9360,35

DPX-V9360,53

CGA-136872,33

CGA-136872,40

Control

Me an 2

Furadan

83.3

92.5

93.3

95.0

93.3

95.8

97.5

93. OA

Insect

Lorsban

78.3

88.3

88.3

83.3

83.3

85.8

90.8

85. 5B

icide

Control

cm

87.5

90.0

91.6

89.2

90.0

85.8

90.0

89.2C

Counter

92.5

94.2

95.8

94.2

93.3

91.6

95.0

93. 8A

Mean^

85.4a

91.2a

92.3a

90.4a

90.0a

89.8a

93.3a

90.3


2 Means in the same row followed by the same capital letter are not significantly different at the 5% level of probability according to Duncan's Test

56


Herbicide

DPX-79406,26

DPX-79406,35

DPX-V9360,35

DPX-V9360, 53

CGA-136872,33

CGA-136872,40

Control

Mean^

Furadan

154.2

154.2

149.2

142.5

139.2

142.5

144.2

146.5A

Insecticide

Lorsban

163.3

165.0

163.3

162.5

160.0

155.0

160.0

161.3B

Control

cm

165.0

167.5

172.5

165.8

170.0

169.2

165.8

168.OC

Counter

160.8

157.5

159.2

154.2

157.5

151.7

159.2

157.2D

Mean^

160.8a

161.1a

161.1a

156.3a

156.7a

154.6a

157.3a

157.5



57

(146.5 cm). These data indicate that these insecticides had

a variable effect on the plant height when measured at 4, 6,

and 8 weeks after planting.

Herbicide Effect

The herbicide effects on corn heights when measured 4,6,

and 8 weeks after planting, averaged over insecticides,

showed no differences (Appendix L, Tables LI, L2, and L3).

Therefore, it was concluded that these herbicides have no

differential effects on corn height.

Interaction Effect

No interaction effects on corn height were observed in the

ANOVA Table (Appendix L, Tables LI, L2, and L3). These data

suggest that no adverse or positive effects of treatment

interactions (herbicides and insecticides) on corn height for

Triumph 2020 was evident.

CHAPTER V

SUMMARY AND CONCLUSIONS

Greenhouse Study

Hybrid effects were apparent on the harvested wet weight

and corn plant heights when measured 4,6, and 8 weeks after

planting. Dekalb 711 had higher harvested wet weights than

did Pioneer 3168 and Triumph 2020. However, when corn plant

heights were measured 4,6, and 8 weeks after planting Pioneer

3168 had the greatest plant height followed by Triumph 2020

and lastly by Dekalb 711. The main effect of herbicides

affected harvest wet weight, harvest dry weight, plant

heights when measured 6 and 8 weeks after planting, and the

sorghum injury rating. CGA-136872 reduced the corn harvest

wet and dry weights, and the plant heights when measured 6

and 8 weeks after planting as compared to the control and

DPX-V9360. However, DPX-V9360 had a soil persistence which

caused serious sorghum injury; whereas, the control (as

expected) and CGA-136872 did not.

In this greenhouse study, no insecticide main effect was

observed. In addition, none of the treatment combinations

(hybrid X insecticide, hybrid X herbicide, insecticide X

herbicide, and hybrid X insecticide X herbicide) had any

significant effects on any of the parameters (corn wet

58

59

weight, corn dry weight, corn plant height and sorghum

injury).

Field Study

Insecticide effects were significant for number of plants

per square meter and corn plant heights when measured 4, 6,

and 8 weeks after planting for the three hybrids. Furadan,

Lorsban, and Counter enhanced the number of plants per square

meter for two of the hybrids as compared to the control.

These three insecticides gave inconsistent results on corn

plant heights when measured 4, 6, and 8 weeks after planting.

No herbicide main effect or herbicide X insecticide

interactions were noted for any of the hybrids relative to

population density or corn plant height measurements.

LITERATURE CITED

1. Aldrich, S. R., and Earl R. Leng. 1966. Modern corn production. P&W Publishing Co., Cincinnati, Ohio.

2. Anderson, W. P. 1983. Weed science principle. West Publishing Co., St. Paul, Minnesota.

3. Arnold, R. N., E. J. Gregory, and D. Smeal. 1988. Effects of herbicides on weeds in field corn grown on coarse-textured soils. Applied Agricultural Research. 3(1):21-23.

4. Banks, P. A. 1989. Implications of tillage on herbicide persistence and subsequent plant growth. Proc. SWSS. 42:92

5. Bhowmik, P. C , and B. M. Bahnson. 1989. Postemergence quackgrass (Elytriaia repens (L.) Nevski.) control in corn. WSSA. 30:5 (Abstr.).

6. Biediger, D. L., D. N. Weaver, P. A. Baumann, J. M. Chandler, and M. G. Merkle. 1989. Phytotoxic interaction between Beacon and soil Insecticides applied to corn. Texas Agr. Exp. Stat. Inf. Rep.

7. Brown, B. A., R. M. Hayes, G. N. Rhodes, Jr., and E. L. Ashburn, 1989. Removal of Johnsongrass interference in corn with CGA-136872 and DPX-V9360. Pro. SWSS. 42:47

8. Bryson, C. T., and C. E. Snipes. 1989. Residual effects of DPX-T9595 on soybeans and sorghum. Proc.SWSS. 42:109.

9. Chenault, E. W., and A. F. Wiese. 1989. Accent, DPX-79406 and Beacon Research. Texas Agr. Exp. Stat. Inf. Rep.

10. Downard, R. W., and 0. E. John. 1985. The Interaction between the Sulfonylurea herbicides and Dichlofop-methyl on control of wild oat (Avena fatual L.). Proc. WSWS. 40:2 6-31

11. Fenton, F. A. 1952. Field crop insects. The Macmillan Company, New York.

60

61

12. Gipson, J. R. 1989. Chemical weeds control. Spring lecture note 1989.

13. Gipson, J. R. 1989. Field crop. Spring lecture note 1989.

14. Gillespie, G. R., P. J. Porpiglia, and J. W. Peek. 1989. Influence of application variables on the herbicidal activity of CGA-136872. WSSA. 30:6 (Abstr.).

15. Gomez, K. A., and A. A. Gomez. 1984. Statistical procedures for agricultural research. John Wiley & Sons, New York.

16. Green, M., G. L. Leek, S. D. Strachan, H. L. Palm, and S. W. Rowe. 1989. DPX-79406 a new postemergence herbicide product for corn. WSSA. 30:4 (Abstr.).

17. Hance, R. J. 1980. Interactions between herbicides and the soil. Academic Inc. London.

18. Hayes, R. M. 1989. Optimizing herbicide activity in no-tillage cropping systems. Proc. SWSS. 42:89.

19. Hays, R. M., K. V. Yeargan, W. W. Witt, and H. G. Haney. 1979. Interaction of selected insecticide-herbicide combinations on soybeans. WSSA. 27:51-54 (Abstr.).

20. Heger, E. A., and S. Glenn. 1989. Control of perennial weeds with DPX-V9360. WSSA. 30:5 (Abstr.).

21. Heinrichs, E. A. 1988. Plants stress-insect interactions. John Wiley & Sons, Inc. New York.

22. Herrmann, J. E., G. N. Rhodes, Jr., and R. M. Hayes. 1989. Efficacy of new postemergence herbicides in corn. Proc. SWSS. 42:49.

23. Johnson, W. G., R.E. Frans, M. R. McClelland. 1989. Weed control and crop response to DPX-V9360 (Accent), CGA-136872 (Beacon) and SD-63596. Proc. SWSS. 42:45.

24. Ketchersid, M. L., J. M. Chandler, and M. G. Merkle. 1989. Factors affecting the phytotoxicity of CGA-136872 to corn. Proc. SWSS. 42:271.

62

25. Kuratle, H., M. Hanagan, W. H. Kenyon, and S. D. Strachan. 1988. A new selective postmergence grass herbicide for corn. WSSA. 28:12-13 (Abstr.).

26. Leek, G. L., L.H. Harvey, and H.K. William. 1987. DPX-V9360. A new selective herbicide for postemergence grass control in corn. Proc. NCWC. conf. 42:47.

27. Locke, J. M., J. M. Chandler ,and D. L. Holshouser. 1989. Corn and Johnsongrass response to sulfonylurea herbicides. Proc. SWSS. 42:52.

28. Martin, J. H., W. H. Leonard, and D. L. Stamp. 1976. Principles of field crop production. Macmillan Publishing Co., Inc., New York.

29. Matsumura, F. 1980. Toxicology of insecticides. Plenum Press, New York and London.

30. Michels, G. J., and R. W. Behle. 1985. An Evaluation of low rates of lorsban for chemical control of greenbug on sorghum. The Texas Agr. Exp. Stat. The Texas A&M Univ. System/College Station, Texas.

31. Monks, D. W., and K. E. Johnson. 1989. Sweet corn response to Accent (DPX-V9360) and Beacon (CGA-136872). Proc. SWSS. 42:155.

32. Morton, C. A., and R. G. Harvey. 1989. DPX-V9360 for control of giant foxtail (Setaria faberi Herrm.) in field corn. WSSA. 30:4 (Abstr.).

33. Mueller, T. C , D. C. Bridges, and P. A. Banks. 1989. Postemergence johnsongrass control in corn. Proc. SWSS. 42:44.

34. Page, B. G., and W. T. Thomson. 1988. The insecticide, herbicide, fungiside quick guide. Thomson Publications, Fresno, California.

35. Porpiglia, P. J., H. A. Collin, and J. W. Peek. 1988. A new corn herbicide. WSSA. 28:13 (Abstr.).

36. Porpiglia, P. J., G. R. Gillespie, and M.D. Johnson. Enhanced CGA-136872 activity in combination with insecticides. WSSA. 30:6 (Abstr.).

63 37. Reynolds, D. B., P. R. Vidrine, J. L. Griffin, P. A.

Richard, and A. L. Perrit. 1989. Rate by timing response of new postemergence herbicide in corn. Proc. SWSS. 42:53.

38. Salam, M. A., and S.Subramanian. 1988. The interaction effects between applied N and insecticides (Carbofuran and phorate) on growth and yield of rice. J. Trop.Agr. 66 (4):297-301.

39. Slack, C. H., R. B. Wells, M. D. Cole, and W. W. Witt. 1989. Performance of CGA-136872, DPX-V9360 and S-63596 in field corn. Proc. SWSS. 42:369.

40. Smith, L. W. 1970. Antagonistic responses with combinations of trifluralin and organic phosphate insecticides. WSSA. 18:21 (Abstr.).

41. Steel, R. G. D., and J. H. Torrie. 1980. Principle and procedures of statistics. McGraw-Hill, New York.

42. Steven, W. E. 1989. Herbicide evaluations in corn. Proc. SWSS. 42:46.

43. Thompson, M. A., W. W. Witt, J. R. Martin, and C. H. Slack. 1989. Interaction effects of DPX-V9360 and organophosphate insecticides on corn. Proc. SWSS. 42:278.

44. Vidrine, P. R. 1989. Comparison of postemergence grass herbicides in corn. Proc. SWSS. 42:50.

45. Waldrop, D. D., and P. A. Banks. 1983. Interactions of herbicides with insecticides in soybeans. WSSA. 31:730-734 (Abstr.).

46. Ware, G. W. 1989. The pesticide book. Thomson Publications, p.41-48.

47. William, C. S. 1989. DPX-V9360: Postemergence weed control in corn. Proc. SWSS.42:48.

48. Witt, W. W., and C. H. Slack. 1989. Interaction of DPX-V9360 and CGA-136872 with soil applied insecticides. WSSA. 30:6 (Abstr.).

49. Worsham, A. D., and E. Saunders. 1989. Johnsongrass control postemergence in corn with DPX-V9360 (Accent), CGA-136872 (Beacon) and SD-63596. Proc. SWSS. 42:51.

G r e e n h o u s e S t u d y

64

Appendix A

Wet Weight

65

66

Table Al. Analysis of variance for corn wet weight at harvest in the greenhouse study.

Source

Block(B)

Hybrid(Hy)

Insecticide(I)

Herbicide (H)

Hy X I

Hy X H

I X H

Hy X I X H

Error

Total

df

3

2

3

2

6

4

6

12

105

143

SS

2330.98

1919.94

421.53

1942.50

775.19

240.61

537.29

236.74

12929.26

21334.04

MS

776.99

959.97

140.51

971.25

129.20

60.15

89.55

19.73

123.13

F

7.80**

1.14

7.89**

1.05

0.49

0.73

0.16

* Significant at the 0.05 level of probability ** Significant at the 0.01 level of probability

67

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G fd CD

Appendix B

Dry Weight

68

69

Table Bl. Analysis of variance for corn dry weight at harvest in the greenhouse study.

Source

Block(B)

Hybrid(Hy)

Insecticide(I)

Herbicide(H)

Hy X I

Hy X H

I X H

Hy X I X H

Error

Total

df

3

2

3

2

6

4

6

12

105

143

SS

44.09

4.27

5.98

91.55

8.47

1.52

9.53

21.15

359.20

545.77

MS

14.70

2.13

1.99

45.77

1.41

0.38

1.59

1.76

3.42

F

0.62

0.58

13.38**

0.41

0.11

0.46

0.52

* Significant at the 0.05 level of probability. * Significant at the 0.01 level of probability.

70

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Appendix C

Corn Height 4 Weeks after Planting

71

72

Table CI. Analysis of variance for corn height measured 4 weeks after planting in the greenhouse study.

Source df SS MS

Block(B)

Hybrid(Hy)

Insecticide(I)

Herbicide (H)

Hy X I

Hy X H

I X H

Hy X I X H

Error

Total

3

2

3

2

6

4

6

12

105

143

42.17

610.33

4.78

3.93

25.70

14.78

24.65

47.40

510.97

1284.73

14.05

305.16

1.59

1.96

4.28

3.69

4.11

3.95

4.87

62.71**

0.33

0.40

0.88

0.76

0.84

0.81


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Appendix D


74

75

Table Dl. Analysis of variance for corn height measured 6 weeks after planting in the greenhouse study.

Source df SS MS

Block(B)

Hybrid(Hy)

Insecticide(I)

Herbicide(H)

Hy X I

Hy X H

I X H

Hy X I X H

Error

Total

3

2

3

2

6

4

6

12

105

143

168.07

1727.85

54.68

392.85

52.62

61.28

70.67

218.84

1804.68

4551.56

56.02

863.92

18.23

196.42

8.77

15.32

11.78

18.24

17.19

50.26**

1.06

11.43**

0.51

0.89

0.69

1.06

* Significant at the 0.05 level of probability. ** Significant at the 0.05 level of probability.

76

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Appendix E


77

78

Table El. Analysis of variance for corn height measured 8 weeks after planting in the greenhouse study.

Source

Block(B)

Hybrid(Hy)

Insecticide(I)

Herbicide (H)

Hy X I

Hy X H

I X H

Hy X I X H

Error

Total

df

3

2

3

2

6

4

6

12

105

143

SS

860.99

2929.39

127.45

3518.36

23.81

206.13

165.76

331.59

4022.14

12185.63

MS

286.99

1454.69

42.48

1759.18

3.97

51.53

27.63

27.63

38.31

F

38.24**

1.11

45.92**

0.10

1.36

0.72

0.72

*.Significant at the 0.05 level of probability. ** Significant at the 0.01 level of probability.

79

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Appendix F

Sorghum Injury

80

81

Table Fl. Analysis of variance for residual sorghum injury in the greenhouse study.

Source df SS MS

Block (B)

Hybrid(Hy)

Insecticide(I)

Herbicide(H)

Hy X I

Hy X H

I X H

Hy X I X H

Error

3

2

3

2

6

4

6

2

7.42

0.10

2.14

2010.93

1.74

1.07

3.74

11.76

2.47

0.05

0.71

1005.46

0.29

0.27

0.62

0.98

0.08

1.19

1673.56**

0.48

0.45

1.04

1.63

105 63.08 0.60

Total 143 2101.97

* Significant at the 0.05 level of probability. * Significant at the 0.01 level of probability.

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Field Study

83

Appendix G

Plants per Square Meter for Dekalb 711

84

85

Table Gl. Analysis of variance for the number of plants per square meter of Dekalb 711 in the field study.

Source df SS MS

Block(B)

Herbicide (H)

Error(a)

Insecticide(I)

H X I

Error(b)

2

6

12

3

18

42

14.88

23.90

28.45

58.03

64.38

197.33

7.44

3.99

2.37

19.34

3.57

4.70

1.68

4.12**

0.76

Total 83 386.99


Appendix H

Corn Height for Dekalb 711

86

87

Table HI. Analysis of variance for corn height measured 4 weeks after planting of Dekalb 711 in the field study.

Source df

Block (B) 2

Herbicide(H) 6

Error(a) 12

Insecticide(I) 3

H X I 18

Error(b) 42

SS

8 3 . 1 7

1 6 . 7 4

2 0 . 8 3

3 1 . 1 8

3 1 . 7 4

6 3 . 3 3

MS

4 1 . 5 8

2 . 7 9

1 . 7 3

1 0 . 3 9

1 . 7 6

1 . 5 1

F

1 . 6 1

6 . 8 8 * *

1 .16

Total 83 246.99


88

Table H2. Analysis of variance for corn height measured 6 weeks after planting of Dekalb 711 in the field study.

Source df SS MS

Block (B) 2

Herbicide (H) 6

Error (a) 12

Insecticide (I) 3

H X I 18

Error (b) 42

1 7 . 6 4

4 3 . 7 8

4 2 . 3 5

4 7 . 0 9

3 7 . 7 4

1 0 0 . 6 7

8 . 8 2

7 . 3 0

3 . 5 3

1 5 . 6 9

2 . 0 9

2 . 4 0

2 . 0 7

6 . 5 5 * *

0 . 8 7

Total 83 289.28


A ^-'jr--

Table H3. Analysis of variance for corn height measured 8 weeks after planting of Dekalb 711 in the field study.

89

Source df SS MS

Block (B)

Herbicide(H)

Error(a) 12

Insecticide(I)

H X I 18

Error (b) 42

273.33

47.90

102.59

406.00

264.00

465.50

136.61

7.98

8.55

135.33

14.67

11.08

0.93

12.21**

1.32

Total 83 1559.24


Appendix I

Plants per Square Meter for Pioneer 3168

90

91

Table II. Analysis of variance for number of plants per square meter of Pioneer 3168 in the field study.

Source df SS MS

Block (B) 2

Herbicide (H) 6

Error(a) 12

Insecticide(I) 3

H X I 18

Error(b) 42

1.17

33.48

68.67

109.18

50.90

170.17

0.58

5.58

5.72

36.39

2.83

4.05

0.97

8.98**

0.70

Total 83 433.56


Appendix J

Corn Height for Pioneer 3168

92

93

Table Jl. Analysis of variance for corn height measured 4 weeks after planting of Pioneer 3168 in the field study.

Source df SS MS

Block(B) 2

Herbicide (H) 6

Error (a) 12

Insecticide(I) 3

H X I 18

Error (b) 42

5 . 8 1

1 1 . 2 8

1 7 . 3 6

4 1 . 8 1

4 2 . 5 2

8 4 . 1 7

2 . 9 0

1 . 8 8

1 . 4 5

1 3 . 9 4

2 . 3 6

2 . 0 0

1 .30

6 . 9 7 * *

1 .18

Total 83 202.95


94

Table J2. Analysis of variance for corn height measured 6 weeks after planting of Pioneer 3168 in the field study.

Source df SS MS

Block(B)

Herbicide (H)

Error(a) 12

Insecticide(I) 3

H X I 18

Error(b) 42

9 8 . 8 8

1 1 9 . 0 7

9 3 . 2 8

1 0 6 . 7 0

3 2 . 5 5

1 8 2 . 5 0

4 9 . 4 4

1 9 . 8 4

7 . 7 7

3 5 . 5 7

1 . 8 1

4 . 3 4

2 . 5 5

8 . 1 9 * *

0 . 4 2

Total 83 632.99


95

Table J3. Analysis of variance for corn height measured 8 weeks after planting of Pioneer 3168 in the field study.

Source df SS MS

Block(B) 2

Herbicide (H) 6

Error(a) 12

Insecticide(I) 3

H X I 18

Error(b) 42

Total 83 1118.57

76.36

110.24

336.48

164.95

132.71

297 .83

38.18

18.37

28.04

54.98

7.37

7.09

0.66

7.75**

1.04


Appendix K

Plants per Square Meter for Triumph 2020

96

97

Table Kl. Analysis of variance for number of plants per square meter of Triumph 2020 in the field study.

Source df SS MS

Block(B) 2 5.78 2.89

Herbicide (H) 6 19.98 3.33 1.54

Error(a) 12 25.88 2.16

Insecticide(I) 3 45.46 15.15 4.29**

H X I 18 73.45 4.08 1.16

Error(b) 42 148.33 3.53

Total 83 318.89


Appendix L

Corn Height for Triumph 2020

98

99

Table LI. Analysis of variance for corn height measured 4 weeks after planting of Triumph 2020 in the field study.

Source df

Block(B) 2

Herbicide (H) 6

Error(a) 12

Insecticide(I) 3

H X I 18

Error(b) 42

SS

4 8 . 0 2

2 0 . 4 8

1 7 . 8 1

6 4 . 2 8

2 6 . 3 8

4 6 . 8 3

MS

2 4 . 0 1

3 . 4 1

1 . 4 8

2 1 . 4 3

1 . 4 6

1 . 1 1

F

2 . 3 0

1 9 . 2 2 * *

1 . 3 1

Total 83 223.81


100 Table L2. Analysis of variance for corn height measured 6 weeks after planting of Triumph 2020 in the field study.

Source df

Block(B)

Herbicide(H)

Error(a) 12

Insecticide(I) 3

H X I 18

Error(b) 42

SS

1 3 4 . 0 0

7 3 . 4 5

8 8 . 3 3

1 4 7 . 9 0

5 4 . 2 6

1 0 2 . 3 3

MS

6 7 . 0 0

1 2 . 2 4

7 . 3 6

4 9 . 3 0

3 . 0 1

2 . 4 4

F

1 . 6 6

2 0 . 2 3 * *

1 .24

Total 83 600.28


101

Table L3. Analysis of variance for corn height measured 8 weeks after planting of Triumph 2020 in the field study.

Source df

Block(B)

Herbicide(H)

Error(a) 12

Insecticide(I)

H X I 18

Error(b) 42

SS

2.17

82.81

91.83

813.56

103.19

142.00

MS

1.08

13.80

7.65

271.19

5.73

3.38

1.80

80.21**

1.70

Total 83 1235.56


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the effects of herbicides and insecticides used and

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