SELECTIVITY 0F ETHOFUMESATB (Z-ETHOXY-2,3-DIHYDRO-
3,3-DIMETHYL-S-BENZOFURANYL METHANESULPHONATE) IN

SUGARBEET (BETA VULGARIS L.) AND ASSOCIATED WEED SPECIES

 

BY

David Neil Duncan

A DISSERTATION

Submitted to
Michigan State University
in partial fulfillment of the requirements
for the degree of

DOCTOR OF PHILOSOPHY

Department of Crop and Soil Sciences

1978

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69/7ggéajfi?

ABSTRACT

SELECTIVITY OF ETHOFUMESATE (2-ETHOXY-2,3-DIHYDRO-

3,3-DIMETHYL—5-BENZOFURANYL METHANESULPHONATE) IN
SUGARBEET (BETA VULGARIS L.) AND ASSOCIATED WEED SPECIES

BY

David Neil Duncan

Preemergence application of the combination of ethofumesate (2-ethoxy-

2,3-dihydro-3,3-dimethy1-S-benzofuranyl methanesulphonate) plus TCA

(trichloroacetic acid) caused greater growth suppression than pyrazon

(S-amino-4-chloro-2-pheny1—3(2H)-pyridazinone) plus TCA when followed by
Sugarbeet

a postemergence herbicide treatment to field grown sugarbeets.
tolerance was least when treatments were applied at the early two-leaf

Combination treatments applied with endothall [7-oxabicyclo
Foliar treat-

stage.
(2,2,1) heptane-2,3-dicarboxylic acid] caused less injury.
ment at the two- to four-leaf stage of sugarbeet gave greater weed con-

Mid-afternoon applications were more selective than either morning

trol.
or evening treatments.

Exposure of plants to ethofumesate severely decreased the epicuti-
cular wax deposition on the leaf surfaces of sugarbeet. Gas-liquid
chromatography indicated ethofumesate decreased the deposition of the
alkanes and Eggfketones but increased that of the long-chain waxy esters

Scanning electron micrographs and cuticular transpiration data further

David Neil Duncan

substantiated the inhibition of wax by ethofumesate. Greater absorption
of 14C-ethofumesate, l4C-desmedipham, and 14C-ethofumesate + 14C-
desmedipham was observed in plants that received preemergence treatments
of ethofumesate and TCA as compared to pyrazon or a control. The basis
for the observed interaction of sequential herbicide combinations was in-
creased absorption of foliar applications due to reduction in epicuticular
leaf wax deposition from soil-applied herbicides.

Further greenhouse and laboratory studies evaluated the basis for
selectivity of both root-applied and foliar-applied ethofumesate on
sugarbeet and several weed species. More root-applied 14C-ethofumesate
was translocated to the leaf tissue of the susceptible pigweed and lambs-
quarter plants than the tolerant sugarbeet and ragweed. Stem tissue of
both sugarbeet and ragweed contained a greater percentage of non-extract-
able residue than pigweed or lambsquarter. The rapid metabolism of
ethofumesate by the tolerant sugarbeet and ragweed, particularly in the
leaf tissue, appeared related to tolerance. Seedlings of the highly
susceptible pigweed and lambsquarter species absorbed greater amounts of
14C-ethofumesate from foliar application than the moderately susceptible
ragweed and tolerant sugarbeet. Very little 14C was translocated from
treated foliage to untreated plant tissue of sugarbeet. All weed species
translocated 14C-ethofumesate to untreated leaf tissue when l4C-ethofume-
sate was applied to seedlings at the two-leaf stage. Only two-leaf pig-
weed and lambsquarter seedlings moved ethofumesate basipetally to the
stem and root components. High percentages of 14C complexed with polar
plant constituents in sugarbeet seedlings. CO2 uptake and evolution were

inhibited for both pigweed and sugarbeet leaves but recovered rapidly in

sugarbeet, depending on age of plant at treatment. The stage of plant

David Neil Duncan

development was the key factor in determining species response to foliar
treatments of ethofumesate in terms of absorption, metabolism, and total

photosynthesis and respiration.

To my beautiful and loving wife, Rose,

for her undaunted support of this project

ii

ACKNOWLEDGMENTS

The author expresses sincere appreciation to his major professor,
Dr. William F. Meggitt, for his guidance, encouragement, and constructive
criticism throughout this project; but particularly for the opportunity
of association and involvement with weed control at Michigan State
University.

Special acknowledgments are extended to Dr. Donald Penner for his
enthusiasm and assistance in the laboratory aspects of the project as
well as critical review of manuscripts, and to Fisons Corporation and
the F G M Beet Sugar Foundation for their financial and technical support.
The assistance given by Drs. Al "Putt" Putnam, George Hogaboam and John
Shickluna for serving on my guidance committee is also gratefully acknow-
ledged.

The author extends a special thanks to his student research assistants,
Bob "Lunder" Lund, Alan McAnulty, and Evelyn Sharbowski. Their efforts

were instrumental in completing this study.

iii

TABLES OF CONTENTS

Page
LIST OF TABLES . . . . . . . . . . . . . . . . . . . . . . . . . . . vi
LIST OF FIGURES . . . . . . . . . . . . . . . . . . . . . . . . . . ix
INTRODUCTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1
CHAPTER 1: INFLUENCE OF PREEMERGENCE APPLIED HERBICIDES AND TIMING
OF APPLICATION ON PHYTOTOXICITY OF POSTEMERGENCE
HERBICIDE APPLICATIONS TO SUGARBEET . . . . . . . . . . 2
Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 2
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
Materials and Methods . . . . . . . . . . . . . . . . . . . . . 4
Results and Discussion . . . . . . . . . . . . . . . . . . . . 6

Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 10

CHAPTER 2: BASIS FOR INCREASED ACTIVITY FROM HERBICIDE COMBI-
NATIONS WITH ETHOFUMESATE ON SUGARBEET . . . . . . . . . 18

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 19
Materials and Methods . . . . . . . . . . . . . . . . . . . . . 19
Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . 23
Discussion . . . . . . . . . . . . . . . . . . . . . . . . . . 25
Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 27

CHAPTER 3: THE BASIS FOR SELECTIVITY OF ROOT-APPLIED
ETHOFUMESATE IN SUGARBEET AND THREE WEED SPECIES . . . . 37

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 37

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 38

iv

Page
Materials and Methods . . . . . . . . . . . . . . . . . . . . . 38
Results and Discussion . . . . . . . . . . . . . . . . . . . . 40
Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 43

CHAPTER 4: PHYSIOLOGICAL BASES OF SUGARBEET TOLERANCE TO FOLIAR
APPLICATION OF ETHOFUMESATE . . . . . . . . . . . . . . 59

Abstract . . . . . . . . . . . . . . . . . . . . . . . . . . . 59
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 60
Materials and Methods . . . . . . . . . . . . . . . . . . . . . 61
Results and Discussion . . . . . . . . . . . . . . . . . . . . 63
Literature Cited . . . . . . . . . . . . . . . . . . . . . . . 67
CHAPTER 5: SUMMARY AND CONCLUSIONS . . . . . . . . . . . . . . . . 83

LIST OF REFERENCES . . . . . . . . . . . . . . . . . . . . . . . . . 86

LIST OF TABLES

Page
CHAPTER 1

1. Sugarbeet response to pyrazon plus TCA preemergence
followed by postemergence herbicide applications at
three stages of sugarbeet development . . . . . . . . . . . . 12

2. Sugarbeet response to ethofumesate plus TCA preemergence
followed by postemergence herbicide applications at
three stages of sugarbeet development . . . . . . . . . . . . 13

3. Weed control for pyrazon plus TCA preemergence followed
by postemergence herbicide applications at three stages
of sugarbeet development averaged over three locations
for 2 years . . . . . . . . . . . . . . . . . . . . . . . . . 14

4. Weed control for ethofumesate plus TCA preemergence
followed by herbicide applications at three stages of
sugarbeet development averaged over three locations
for 2 years . . . . . . . . . . . . . . . . . . . . . . . . . 15

5. Sugarbeet response and weed control for postemergence
herbicide applications at three times of day in
East Lansing, Mich., 1977 . . . . . . . . . . . . . . . . . . 16

CHAPTER 2
1. Influence of preemergence herbicide treatment on the
activity of ethofumesate plus desmedipham combination
applied postemergence in field studies at 1.68 + 0.84
kg/ha during 1976 and 1977 . . . . . . . . . . . . . . . . . . 28

2. Effect of preemergence herbicide treatment on major
sugarbeet wax components determined by GLC . . . . . . . . . . 29

3. Cuticular transpiration of sugarbeet leaves in response
to preemergence herbicide treatment . . . . . . . . . . . . . 30

4. Influence of preemergence treatment on absorption of 14C-
herbicides after 3 hr exposure . . . . . . . . . . . . . . . . 31

vi

5. Influence of preemergence treatment on absorption of 14C-

herbicides after 24 hr exposure
CHAPTER 3

l. Uptake of l4C-ethofumesate by sugarbeet and three weed
species grown in nutrient solution containing 4 x 10'6 M
ethofumesate .

2. Distribution of 14C in sugarbeet and three weed species
grown in nutrient solution containing 4 x 10'6 M
ethofumesate after 1, 3, and 7 days exposure .

3. Percent non-extractable radioactivity after l4C-
ethofumesate absorption for leaf, stem, and root components
of 4 species after 1, 3, and 7 days exposure .

4. Metabolites of 14C-ethofumesate and corresponding TLC Rf
values obtained from leaf segments of four species harvested
after 1, 3, and 7 days exposure

5. Metabolism of 14C-ethofumesate in leaf, stem, and root
components of four species after 1, 3, and 7 days exposure .

6. Metabolism of l4C-ethofumesate in the dichloromethane-
soluble fraction as a function of plant species and
component and time of exposure .

7. Dichloromethane-soluble metabolites released by acid
hydrolysis of the water-soluble fraction .

CHAPTER 4

1. Absorption of foliar applied 14C-ethofumesate by sugarbeet
and three weed species as influenced by stage of growth at
application and time of exposure . . . .

2. Distribution of l4C-ethofumesate 24 hr after foliage appli-
cation to sugarbeet and three weed species as influenced
by stage of growth at application

3. Metabolism of foliar applied 14C-ethofumesate to four plant
species at the two-leaf stage of growth . .

4. Metabolism of foliar applied l4C-ethofumesate to four plant
species at the four-leaf stage of growth .

S. Metabolism of foliar applied 14C-ethofumesate to four plant

species at the six-leaf stage of growth

vii

Page

. 32

. 44

. 45

. 46

. 47

. 48

. 49

. 50

. 68

. 69

. 7O

. 71

. 72

Page

Percent of initial total photosynthesis of two species
influenced by postemergence herbicide application and
stage of growth at treatment . . . . . . . . . . . . . . . . . 73

Percent of initial dark respiration of two species as

influenced by postemergence herbicide application and
stage of growth at treatment . . . . . . . . . . . . . . . . . 74

viii

LIST OF FIGURES

CHAPTER 1
1. Molecular structure of ethofumesate
CHAPTER 2
1. Photograph of upper surface of first two tree sugarbeet

leaves. Control (1) and ethofumesate-treated preemergence
at 2.24 kg/ha (r)

Scanning electron micrographs of the upper surface of
fresh sugarbeet leaves from control (above) and ethofumesate-
treated (below) plants, lOOOx

CHAPTER 3

1.

Translocation of 14C-ethofumesate in sugarbeet. The
radioautograph (A) after 1, 3, and 7 days exposure to
treatment (left to right) and corresponding plant
specimen (B)

Translocation of 14C-ethofumesate in ragweed. The
radioautograph (A) after 1, 3, and 7 days exposure to
treatment (left to right) and corresponding plant
specimen (B)

Translocation of 14C-ethofumesate in redroot pigweed. The
radioautograph (A) after 1, 3, and 7 days exposure to
treatment (left to right) and corresponding plant

specimen (B) .

The translocation of 14C-ethofumesate in lambsquarter. The
radioautograph (A) after 1, 3, and 7 days exposure to
treatment (left to right) and corresponding plant

specimen (B) .

CHAPTER 4

1.

Translocation of 14C-ethofumesate in sugarbeet. The
radioautographs (A) at the two-, four-, and six-leaf
stages of growth (left to right) and corresponding plant
specimens (B). Arrows indicate treated leaves . .

ix

Page

17

. 34

. 36

. 52

. 54

. 56

. 58

. 76

Page

Translocation of 14C-ethofumesate in common ragweed. The
radioautographs (A) at the two-, four-, and six-leaf

stages of growth (left to right) and corresponding plant
specimens (B). Arrows indicate treated leaves . . . . . . . . 78
Translocation of 14C-ethofumesate in redroot pigweed. The
radioautographs (A) at the two-, four-, and six-leaf

stages of growth (left to right) and corresponding plant
specimens (B). Arrows indicate treated leaves . . . . . . . . 8O

Translocation of 14C-ethofumesate in common lambsquarter.
The radioautographs (A) at the two-, four-, and six-leaf
stages of growth (left to right) and corresponding plant
specimens (B). Arrows indicate treated leaves . . . . . . . . 82

INTRODUCTION

Sugarbeet production in Michigan is rapidly evolving toward total
mechanization. The use of herbicides for weed control is often credited
with providing the impetus for this change. It is estimated that 50% of
the sugarbeet acreage will receive postemergence herbicides in 1978, an
increase of 45% over a 10-year period, with nearly 100% receiving pre-
emergence treatment (29). This rapid increase in the use of both pre-
and postemergence herbicides is indicative of the development of success-
ful, selective herbicides for broad spectrum weed control, and a greater
understanding of the various factors influencing their selectivity.

Ethofumesate has recently been introduced for selective weed control
in sugarbeet as both a soil- and foliar-applied herbicide (14,25). To
help maximize weed control and minimize crop damage with ethofumesate,
research was conducted to (1) determine the influence of preemergence
soil-applied herbicides and timing of application on phytotoxicity of
foliar ethofumesate applications in the field (2) determine the basis for
increased activity with ethofumesate combinations, and (3) evaluate the
physiological bases for sugarbeet tolerance to both pre- and postemergence

applications of ethofumesate.

CHAPTER 1

INFLUENCE OF PREEMERGENCE APPLIED HERBICIDES AND TIMING
OF APPLICATION ON PHYTOTOXICITY OF POSTEMERGENCE HERBICIDE

APPLICATIONS TO SUGARBEET (BETA VULGARIS)

 

ABSTRACT

The influence of previously applied preemergence herbicides, stage

of sugarbeet (Beta vulgaris L.) growth, and timing of application on

 

activity of postemergence applications of ethofumesate (2—ethoxy-2,3-
dihydro-3,3-dimethyl-S-benzofuranyl methanesulphonate) and other herbi-
cides used for weed control in sugarbeets were examined in the field.
Preemergence application of the combination of ethofumesate plus TCA
(trichloroacetic acid) caused greater growth suppression than pyrazon
(S-amino-4~chloro-2-pheny1-3(2H)-pyridazinone) plus TCA when followed by
a postemergence herbicide treatment to field grown sugarbeets. Sugar—
beet tolerance was least when treatments were applied at the early two-
leaf stage. Combination treatments applied with endothall [7-oxabicyclo
(2,2,1) heptane-2,3-dicarboxylic acid] caused less injury. Foliar treat-
ment at the two to four-leaf stage gave greater weed control. Mid-
afternoon applications were less phytotoxic and provided equal or greater

weed control compared to morning or evening treatments.

INTRODUCTION

Total mechanization of sugarbeet production in Michigan must employ
both preemergence and postemergence chemical application for weed control.
Less than 10 years ago only 5% of the Michigan sugarbeets were treated
with postemergence herbicides. The prediction for 1978 is that 50% will
receive postemergence herbicides with nearly 100% receiving preemergence
herbicides. This rapid increase in the use of both pre- and postemergence
herbicides is indicative of the development of successful selective herbi-
cides for broad spectrum weed control.

An understanding of the various factors influencing the selectivity
of herbicides provides a basis for effective weed control with minimal
crop damage. Ethofumesate (Figure 1) has recently been introduced for
selective weed control in sugarbeets (7,12). Preemergence applications
of ethofumesate offer weed control similar to that with pyrazon but with
significantly greater persistence in the soil (l4). Postemergence appli-
cations of ethofumesate in combination with desmedipham (ethyl m-hydroxy—
carbanilate carbanilate) control a broad spectrum of broadleaved weeds;
however, this mixture at a normal use rate may injure sugarbeet seedlings
(5,8,11). Tolerance of the sugarbeet to mixtures of ethofumesate and
desmedipham is dependent on the stage of sugarbeet growth at the time of
application and the amount of desmedipham in the mixture (8). Foliar
growth is suppressed most when the herbicides are applied at the cotyle-
donary stage. The interaction between preplant incorporated applications
of cycloate (S-ethyl N-ethylthiocyclohexanecarbamate) and postemergence
applications of phenmedipham (methyl m-hydroxycarbanilate m-methylcarban-

ilate) demonstrated the preconditioning of sugarbeet and surviving weeds

to varying degrees of injury, depending on stage of growth (4). Environ—
mental conditions can also alter the activity of herbicides (10). High
temperature and light intensity have been shown to increase the injury
to sugarbeets following treatment with phenmedipham (3) and desmedipham
(2). Injury to sugarbeets treated with phenmedipham and desmedipham was
greater when treatments were made in the early morning than in late after-
noon (13,15). Weed control was also altered by timing of application
(4,9).

The objectives of this study were to examine the influence of pre-
viously applied herbicides, stage of growth, and timing of application on
phytotoxicity of postemergence herbicides used for weed control in sugar-

beet.
MATERIALS AND METHODS

Studies were conducted at various locations (Saginaw Co.-I, Lenawee
Co.-II, and Tuscola Co.-III) in Michigan utilizing grower sugarbeet
fields and at the Michigan State experiment station. Plot size was four
or six 70-cm wide rows by 12 m long arranged in a randomized split block
design with three or four replications. .Sugarbeet 'USH20' seed was
planted to final stand and herbicides applied broadcast with a tractor
mounted sprayer delivering 215 1/ha at 2.1 kg/cm2 pressure.

The interactions of preemergence herbicide treatment, stage of crop
development, and postemergence herbicide treatment were evaluated in
1976 and 1977 at three locations per year. Soil texture in the plots was
classified as a sandy clay loam for two locations, sandy loam for the

third, and varied in organic matter content from 2.4 to 12.0%. Two

preemergence herbicide combinations, pyrazon plus TCA and ethofumesate
plus TCA, were evaluated at rates dependent on organic matter content.
Rates of pyrazon were 3.36, 4.48, or 6.72 kg/ha and 2.24 or 3.36 kg/ha
for ethofumesate. The rate for TCA remained constant at 6.72 kg/ha.
Sugarbeet seedlings were sprayed at the cotyledon to early two-leaf, two
to four-leaf, and six to eight-leaf stages of growth. Weed species were
approximately equal to or slightly larger in size than the sugarbeet.
Five herbicides were applied in 12 combinations at rates previously

shown to minimize crop injury and maximize weed control. Growth suppres-
sion, stand count, and weed control were assessed 7 to 10 days after each
postemergence herbicide treatment. Handweeding and/or mechanical cultiva-
tion was employed for additional weed control after completion of evalu-
ations to eliminate the effect of competition on yield. Sugarbeet roots
were harvested and weighed in late October. Juice (120 ml) from samples
of roots was taken from plots at two locations and analyzed for percent
recoverable sugar at Michigan Sugar Company, Saginaw, Michigan. All data
except for yields are expressed as percent of the non-treated control

and averaged over two years and three locations.

The study on the interaction of time-of-day at postemergence treat-
ment and herbicide was evaluated at one location in 1977. Pyrazon plus
TCA (2.2 + 6.72 kg/ha) was applied preemergence to a sandy loam soil with
1.5% organic matter. Two to four-leaf sugarbeets and 5 to 8 cm tall weeds
were sprayed mid-morning (9-10 am), mid-afternoon (2-3 pm), and evening
(7-8 pm). Postemergence herbicide applications were made on June 13, a
sunny, cloudless day with temperatures of 24°C at 10 am, 32°C at 3 pm,
and 26°C at 8 pm. The temperature reached a high of 31°C the following

day. Wind velocity was measured at 7.4 to 11.1 km/hr peaking at 11 am.

There was 0.38 cm rainfall 4 hr prior to the first application and no

rainfall for 72 hr thereafter.

RESULTS AND DISCUSSION

Sugarbeet injury from postemergence herbicide applications was asso-
ciated with the preemergence herbicide used, stage of sugarbeet growth
at time of treatment, and the specific foliar herbicide applied (Tables
1 and 2). A preemergence application of ethofumesate plus TCA was re-
sponsible for greater sugarbeet growth suppression following postemergence
herbicide applications than was the pyrazon plus TCA combination. This
effect caused by preemergence application of ethofumesate plus TCA was
evident following most of the postemergence herbicide treatments at the
three stages of growth, but did not manifest itself in significant stand
reduction or yield loss. For example, the highly effective ethofumesate
plus desmedipham plus endothall foliar treatment applied at the two-,
four-, and six-leaf stages caused 10, 46, and 30 percent more injury,
respectively, following the preemergence combination of ethofumesate plus
TCA. The basis for this interaction appears to be inhibition of epicuti-
cular wax deposition on sugarbeet leaves due to preemergence application
of ethofumesate which resulted in enhanced uptake of foliar applied chemi-
cals (6).

Sugarbeet injury was greatest when postemergence herbicide treat-
ments were applied to plants in the early two-leaf stage, regardless of.
preemergence herbicide treatment. Similar results have been reported on
sugarbeet tolerance to ethofumesate and desmedipham (8,11). Foliar

growth, crop stand, and root yield were significantly reduced by seven

of the twelve postemergence herbicide treatments applied at the early
two-leaf stage. Ethofumesate applied alone and in combination with oil
concentrate or endothall, desmedipham plus endothall, and pyrazon plus
desmedipham plus endothall provided the greatest margin of safety at

the two-leaf stage. Suppression of foliar growth seldom resulted in
significant stand reduction when evaluating the two to four- and six to
eight—leaf stages, and never in yield reduction. This improved tolerance
indicates decreased uptake or enhanced detoxication of the herbicide by
the older, more mature sugarbeet foliage.

For both preemergence herbicide treatments at the three stages of
sugarbeet growth, plant injury was greatest following a combination post-
emergence herbicide treatment. Ethofumesate plus desmedipham and desmedi-
pham plus phenmedipham postemergence combinations were particularly in-
jurious at the three growth stages. The exceptions were the combinations
containing endothall (Tables 1 and 2). Endothall provided a protective
effect, especially for treatments applied at the early two-leaf stage
where potential injury was greatest. When the various growth parameters
were analyzed for main treatment effects, it was found that sugarbeets
were less tolerant to postemergence applications of desmedipham than
ethofumesate. This difference in tolerance decreased with increased
maturity of the sugarbeet.

A comparison between preemergence treatments revealed few signifi-
cant differences in weed control (Tables 3 and 4). The ethofumesate plus
TCA combination provided an improved margin of control for the few treat-
ments where differences were measured, including the no postemergence
treatment. A significant interaction for weed control was measured

between postemergence herbicide treatment and stage of sugarbeet

development at time of application. Almost without exception, the foliar
treatment at the two to four-leaf stage resulted in significantly greater
weed control. The treatments most phytotoxic to the sugarbeet were also
most effective for weed control regardless of preemergence treatment or
stage of growth. Combination treatments of ethofumesate plus desmedipham,
pyrazon plus desmedipham, and desmedipham plus phenmedipham provided im-
proved weed control compared to singular treatments of ethofumesate or
desmedipham at all growth stages. Endothall in combination with other
herbicides did not diminish weed control. Therefore, endothall could
effectively increase the margin of selectivity when applied to sugarbeets
in Michigan.

No significant difference in recoverable sugar content was observed
due to any of the main effects or treatment interactions.

Sugarbeet response and weed control were also found to be dependent
on the time of day postemergence treatments were applied (Table 5). Mid—
afternoon applications of the herbicide treatments resulted in less sugar-
beet injury and greater weed control, except for ethofumesate applied
alone. The desmedipham plus ethofumesate plus oil concentrate combina-
tion applied mid—morning resulted in significant stand loss and root
yield reduction compared to the other times of application and the two
herbicides alone. Apparently, yield loss without significant stand reduc-
tion was due to less weed control activity. Ethofumesate applied alone
at all times of day provided greater safety but poor weed control re-
sulting in reduced root yield.

Because most sugarbeets in Michigan are planted at a rate calculated
to give the final stand, the influence of herbicide combinations and

timing of foliar applications on both crop tolerance and weed control

are important. Mixtures of desmedipham plus ethofumesate or phenmedipham
applied postemergence following a preemergence herbicide treatment provide
broad spectrum weed control in Michigan sugarbeet fields. To maximize
weed control and minimize sugarbeet injury the postemergence mixtures
should be applied at the two to four-leaf stage of sugarbeet growth.

From the environmental conditions of temperature, light intensity,
humidity, wind speed, and precipitation, it appears that temperature and
light intensity are most related to sugarbeet injury following treatment
with desmedipham and phenmedipham (1,2,15). Based on these studies,
sugarbeet injury will also vary substantially on preemergence treatment

and stage of growth at application.

10.

11.

12.

13.

10

LITERATURE CITED

Arndt, F., R. Rusch, H. Benzner, and K. V. Gierke. 1970. Die
Beeinflussung der Selektivitat von phenmedipham durch verschiedene
faktoren. Z. Pfanzenkr. Sonderh. V:89-93.

Bethlenfalvay, G. and R. F. Norris. 1975. Phytotoxic action of
desmedipham: Influence of temperature and light intensity.
Weed Sci. 23:499-503.

Bischof, F., W. Koch, J. C. Majumdar, and F. Schwerdtle. 1970.
Retention, penetration and verlust von phenedipham in Abhangigkeit
von einigen factoren. A. Pflanzenkr. V: Sonder. pp. 95-102.

Dawson, J. H. 1975. Cycloate and phenmedipham as complimentary
treatments in sugarbeet. Weed Sci. 23:478-485.

Duncan, D. N., W. F. Meggitt, and D. Penner. 1978. Increased acti-
vity from interactions of ethofumesate combinations in sugarbeet.
Weed Sci. Soc. Amer. Abstr. p. 94.

Duncan, D. N., W. F. Meggitt. 1977. Sugarbeet weed control evalua4
tions for field and lab - 1976. Proc. 19th Reg. Meeting Amer.
Soc. Sugarbeet Technol. pp. 38—41.

Ekins, W. L. and C. H. Cronin. 1972. NC 8438, a promising new broad
spectrum herbicide for sugarbeet. J. Amer. Soc. Sugarbeet
Technol. 17:134-143.

Eshel, Y., E. E. Schweizer, and R. L. Zimdahl. 1976. Sugarbeet
tolerance of postemergence applications of desmedipham and
ethofumesate. Weed Res. 16:249-254.

Eshel, Y., E. E. Schweizer, and R. L. Zimdahl. 1976. Basis for in-
teractions of ethofumesate and desmedipham on sugarbeet and weeds.
Weed Sci. 24:619-626.

Hammerton, J. L. 1967. Environmental factors and susceptibility to
herbicides. Weeds 15:330-336.

Holmes, H. M., R. K. Pfeiffer, and W. Griffiths. 1974. Preemergence
and postemergence use of ethofumesate in sugarbeet. Proc. 12th
Br. Weed Control Conf. 493-501.

Laufersweiler, H. and C. M. Gates. 1972. Response of weeds and
sugarbeets to EP—475, a phenmedipham analog. J. Amer. Soc.
Sugarbeet Technol. 17:73-110.

Norris, R. F. and R. A. Lardelli. 1976. Influence of time of day
at spraying on activity of phenmedipham and desmedipham. Res.
Prog. Rep., West Soc. Weed Sci. pp. 143-146.

11

14. Schweizer, E. E. 1976. Persistence and movement of ethofumesate
in soil. Weed Res. 16:37-42.

15. Winter, S. R. and A. F. Wiese. 1978. Phytoxicity and yield re-
sponse of sugarbeet (Beta vulgaris) to a mixture of phenmedipham
and desmedipham. Weed Sci. 26:1—4.

 

212

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CHAPTER 2

BASIS FOR INCREASED ACTIVITY FROM HERBICIDE COMBINATIONS WITH

ETHOFUMESATE ON SUGARBEET (BETA VULGARIS)

 

ABSTRACT

Differences in susceptibility of sugarbeet (Beta vulgaris L.) to

 

preemergence application of ethofumesate (2-ethoxy-2,3-dihydro-3,3—
dimethyl—S-benzofuranyl methanesulphonate), pyrazon (S-amino-4-chloro-2-
phenyl-3(2H)-pyridozinone) and TCA (trichloroacetic acid) were evaluated
in several combination treatments. Exposure of plants to ethofumesate
severely decreased the epicuticular wax deposition on the leaf surfaces.
Separation of epicuticular wax into major components by gas-liquid chroma-
tography indicated that ethofumesate decreased the deposition of the
alkanes and sggfketones but increased that of long-chain waxy esters.

TCA also decreased the deposition of the alkane and ketone components but
not of the waxy esters. Waxes were unaffected by pyrazon. Scanning elec-
tron micrographs and cuticular transpiration data further substantiated
the inhibition of wax by ethofumesate. Differential inhibition of wax
showed the importance of epicuticular waxes in retarding the absorption
of radiolabeled herbicides. Greater absorption of 14C-ethofumesate, l4C-
desmedipham, and 14C-ethofumesate + 14C-desmedipham was observed in plants
that received preemergence treatments of ethofumesate and TCA as compared

to pyrazon or a control. The basis for the observed interaction of

18

19

sequential herbicide combinations was increased absorption of foliar
applications due to reduction in epicuticular leaf wax deposition from

soil-applied herbicides.

INTRODUCTION

Current weed control practices in sugarbeet frequently result in
sequential herbicide combinations. For example, postemergence herbicides
may follow the use of preplant incorporated or preemergence herbicides.
Whenever herbicide combinations are used, the potential for interaction
exists. The ramifications of these interactions have recently been re-
viewed by Putnam and Penner (10).

It has been reported that soil treatments of ethofumesate reduced
the weight of epicuticular wax on the surface of cabbage (Brassica
oleracea var. capitata) leaves (8). In addition, preliminary field
investigations indicated ethofumesate-treated sugarbeets were less toler-
ant to foliar applied herbicides than were pyrazon-treated plants. This

study was designed to determine the basis for this difference in suscepti-

bility.

MATERIALS AND METHODS

Field Studies

 

Trials were conducted at two locations (Bay Co.-I and Lenawee Co.—II)
.1“ Michigan in 1976 and 1977 to evaluate combination effects of preemerg-
ence and postemergence herbicide applications on sugarbeet. Two preemerg-

ence ‘combinations, pyrazon plus TCA and ethofumesate plus TCA, were

20

evaluated. Rates of pyrazon were either 3.36 or 4.48 kg/ha and for etho-
fumesate, 2.24 or 3.36 kg/ha depending on soil type and organic matter
content. TCA was applied at 6.72 kg/ha. The postemergence treatment
evaluated was the combination ethofumesate plus desmedipham at 1.68 +
0.84 kg/ha at the two to four-leaf stage. Plot size was four or six 70-
cm wide rows and 12 m in length arranged in a randomized complete block
design with three replications. Sugarbeet 'USH 20' seed was planted to
final stand, and herbicides applied broadcast with a tractor-mounted
sprayer delivering 215 l/ha at 2.1 kg/cm2 pressure. Growth reduction
ratings were taken 10 to 14 days after postemergence herbicide treatment.
Root yield was evaluated in late October. Handweeding and/or mechanical
cultivation was employed to eliminate the effect of weed competition on

yield.

Greenhouse and Laboratory Studies

 

Sugarbeet 'USH 20' seed were planted in 946-ml waxed cups filled
with greenhouse potting soil (8% organic matter). Herbicides and herbi-
cide mixtures were sprayed preemergence on the soil surface in an experi-
mental spray chamber at a volume of 950 l/ha and a pressure of 2.1 kg/cm2
with an 80-degree nozzle. Plants were grown outdoors or in the greenhouse
supplemented with mercury halide lamps to provide a 16 hr day and increase
epicuticular wax deposition on leaf surfaces. The emulsifiable formula-
‘tion of ethofumesate and liquid concentrate formulation of sodium trichloro-
acetate (TCA) were used with an active ingredient content of 21 and 47%
(w/v), respectively. A 75.5% wettable powder formulation of pyrazon was

Ixsed. Experiments were conducted in a randomized complete block design

21

with four replications and repeated twice. All data was analyzed by
computer for variance and separation of means.

Analysis g£_epicuticular waxes. When the sugarbeet plants reached
the fully-expanded two-leaf to early four-leaf stage of development, the
first two leaves were excised and allowed to wilt slightly to insure
stomatal closure. Leaves were dipped for 5 sec in each of three succes-
sive 100 ml portions of glass distilled chloroform and the extract com-
bined. Leaf area was measured with an automatic area meter (Lambda
Instruments). Values reported are the means of two experiments, four
replications per treatment with 32 leaves per replication.

A 30 ml aliquot of the chloroform extract of the epicuticular wax
was filtered through Whatman No. 1 filter paper, evaporated at room
temperature under a forced air stream, and the wax redissolved in one ml
of chloroform for gas-liquid chromatography (GLC) analysis. The GLC
system used a hydrogen flame detector interfaced with a recorder and
Digital PD? 11 computer. The column was 1.7 m in length and packed with
3% Dexil 300. The column temperature was 260°C, detector temperature
360°C and inlet line 260°C. The carrier gas was nitrogen. The areas of
the major peaks were measured by the computer, converted to a per cm
leaf area basis, and expressed as percent of control. The major peaks
were classified by methods previously described (8). Separation of the
wax extract into major chemical classes was achieved by thin layer chroma-
tography using 250 um silica gel G plates prewashed in benzene. The
separation was visualized by spraying a 2.5 cm strip with 34 N H2804 and
heating to 160°C for 15 min. Strips not subjected to visualization adja-
cenrt to visualized spots were scraped, eluted with 5 ml chloroform, dried,

aJui redissolved in 1 m1 chloroform for GLC analysis.

22

Scanning electron microscopy (SEM). Scanning electron micrographs

 

were made with an International Scientific Instruments Super Mini-I SEM
of the adaxial surface of fresh sugarbeet leaves. Micrographs were made
of the second true leaf of control plants and plants receiving 2.24 kg/ha
ethofumesate. Pieces (4 by 8 mm) were cut from each leaf at one side of
the midvein. The leaf pieces were placed abaxial surface down upon the
adhesive side of a 1 cm2 strip of silver metallic tape that had been pre-
viously glued to the top of an aluminum SEM stub. The stubs were then
placed in the SEM and micrographs taken on Polaroid type 107 film at 5 kv
acceleration potential. The process consumed less than 10 min from the
time the leaf pieces were first cut. Of primary interest was the change
in fine-structure of the wax bloom of treated plants.

Cuticular transpiration. The effect of the preemergence herbicide

 

treatment on the rate of transpiration through the cuticle was determined
by measuring the rate of water loss from excised sugarbeet leaves. The
first two true leaves were removed and placed in aluminum pans so as not
to overlap. A dewaxed control was prepared by immersing leaves from
control plants into chloroform for 15 sec. The pans were weighed at O
and l, 2, 4, 8, and 24 hr after exposure to these conditions. The weight
of water lost from the leaves during each time period was calculated. A
:regression coefficient (equal to percent water lost per hr) was calculated
for each treatment from initiation of the experiment until 90% of the
«wriginal water was lost or 24 hr, whichever came first. Stomata on the
lexcised leaves closed after 0.3 hr- Values presented are the mean of

four'replications.

Foliar uptake p£_14C-ethofumesate and L4C-desmedipham. Ethofumesate

 

was uniformly labeled in the benzofuranyl ring (sp. act. 1.34 uCi/mole).

23

Desmedipham was radiolabeled with 14C in the m-aminophenol ring (sp. act.
1.95 uCi/mole). The radiolabeled herbicides were dissolved in ethanol
and additional formulated herbicide added to obtain the desired concentra-
tions. A 10 ul drop containing 0.1 uCi of herbicide was placed on the
upper leaf surface of the first two true leaves and spread uniformly with
the rounded end of a glass rod. Concentrations approximated the use

rate for foliar application. At the two sampling dates, 3 and 24 hr, the
treated leaves of each plant were harvested and rinsed with 20 ml of 50%
ethanol to remove any remaining herbicide. After the leaf area was
measured, the leaves were frozen on dry ice and then freeze-dried. A
Packard 306 Tri-Carb Sample Oxidizer was used to combust the tissue.

Released 14CO was trapped with 12 ml Carbo-sorbR and further diluted

2
with 10 ml PermafluorR V liquid scintillation cocktail for carbon-l4.
The vials containing the sample were radioassayed for 10 min with a liquid

scintillation spectrometer. Data is expressed as percent 14C absorbed of

the total applied to the leaf.

RESULTS

Field Studies

 

Reduction of sugarbeet growth was significantly greater when the
postemergence combination of ethofumesate plus desmedipham was applied
subsequent to a preemergence herbicide treatment compared to the preemerg-
ence only treatment (Table 1). Since the postemergence herbicide treat-
ment caused no apparent visual difference among plants not receiving a
preemergence treatment, this increased injury (1 to 18% for pyrazon + TCA

and 3 to 32% for ethofumesate + TCA), can be attributed to a preconditioning

24

of the sugarbeet by the preemergence herbicide. Root yields were un-
affected by the treatments. Visual observations revealed an ethofumesate-
induced leaf surface alteration on sugarbeet (Figure 1). Leaves appeared

glossy when compared to those receiving a preemergence treatment of

pyrazon.

Greenhouse and Laboratory Studies

Wax studies. Sugarbeet leaf wax was separated into three major com-

 

ponents and identified by GLC procedures (Table 2). The ethofumesate
treatment significantly decreased the deposition of C-29 alkane and 392'
tone components as compared to the control and pyrazon treatments., TCA,
a known inhibitor of leaf waxes (1,6,7), also reduced these long-chain
wax fractions. In combination with ethofumesate, TCA had little effect
on the epicuticular wax content when compared with ethofumesate alone;
but in combination with pyrazon, TCA significantly altered the wax deposi-
tion compared to pyrazon alone. Ethofumesate applied alone and in combi-
nation with TCA significantly increased the deposition of long-chain waxy
esters, a component comprising only 5% of the total recovered by GLC.
Scanning electron micrographs of sugarbeet epicuticular wax from
ethofumesate treated and non-treated leaves are shown in Figure 2. The
crystalline fine-structure was entirely eliminated by preemergence
ethofumesate treatments.
Cuticular transpiration of sugarbeet leaves was increased significant—
lgr by all treatments except pyrazon (Table 3). With exception of the

(flilorofOrm-washed control, the two ethofumesate treatments lost the

grmxrtest percentage of water per hour (15.9% for ethofumesate and27.9%

25

for ethofumesate plus TCA).

Postemergence herbicide absorption study. Contrary to a previous
report (3), single applications of 14C-ethofumesate and 14C-desmedipham
were similarly absorbed, both for the control and preemergence herbicide
treated plants (Tables 3 and 4). The exception was the increased absorp-
tion of ethofumesate when applied over ethofumesate preemergence-treated
sugarbeets. For all preemergence herbicide treatments the combination
postemergence treatment resulted in significantly greater absorption
compared to application of individual postemergence herbicides. Ethofume—
sate pre-treatments caused the greatest increase in foliar absorption of
the 14C-herbicides. Only the preemergence application of the ethofumesate
plus TCA combination caused significantly greater 14C absorption than that
obtained from each component of the mixture. The TCA in the pyrazon plus
TCA combination contributed most to the increased absorption of all foliar
treatments. Other than a general increase in uptake after 24 hr of ex-
posure, no major differences were noted between the two times of exposure

(Tables 4 and 5).

DISCUSSION

Data from the 2-year field study confirmed the ethofumesate-induced
Ixreconditioning of sugarbeet to increased growth reduction upon foliar
treatment. Based on the glossy appearance of ethofumesate treated leaves,
tflie hypothesis that such treatments reduced epicuticular wax production
tc> cause increased susceptibility to herbicide sprays was tested.

Data from the various aspects of the wax study clearly indicate

lnaxflced inhibition by ethofumesate of deposition of epicuticular waxes on

26

developing sugarbeet leaves. Although ethofumesate differs considerably
from EPTC (S-ethyl-N,N-di-n-propy1 thiocarbamate) and TCA in structure,
it had a similar and even greater effect on epicuticular wax deposition.
Because ethofumesate increased the deposition of long-chain esters and
decreased the C-29 alkane and C-29 sgpfketone components, the mechanism
of action could be explained by inhibition of fatty acid elongation in
the elongation-decarboxylation pathway of epicuticular wax synthesis.
Similar interpretations have been advanced by Leavitt et a1. (8) for
ethofumesate-induced alterations in wax and by Flore (4) for EPTC-induced
surface wax alterations on cabbage. In addition to a reduction in epicuti-
cular wax production, ethofumesate caused changes in the surface fine-
structure (Figure 2).

The preemergence herbicide treatments reduced deposition of major
wax components and increased cuticular evapotranspiration. The decrease
in epicuticular wax caused greater absorption of foliar applied 14C-
lmerbicide, both alone and as combinations, when applied to the first
'two true leaves of plants in the early four-leaf stage of development.
TTEis would explain the herbicide interaction observed in the field study.
Similarly, increased sensitivity of EPTC and TCA treated plants to sub-
sexpient herbicide sprays (2,5,9) suggested increased penetration. Davis

arui Dusbabek (1) demonstrated increased uptake of 14C-pesticides by peas

 

(Bi—sum sativum L.) exposed to the thiocarbamate, diallate [S—(2,3-

dicfliloroallyl)diisopropylthiocarbamate].

10.

27

LITERATURE CITED

Davis, D. G. and K. F. Dusbabek. 1973. Effect of diallate on
foliar uptake and translocation of herbicides in pea. Weed Sci.
21:16-18.

Dewey, 0. R., P. Gregory, and R. K. Pfeiffer. 1956. Factors affect-
ing the susceptibility of peas to selective dinitro-herbicides.
Proc. 3rd Brit. Weed Control Conf. 1:313-326.

Eshel, Y., R. L. Zimdahl, and E. E. Schweizer. 1976. Basis for
interactions of ethofumesate and desmedipham on sugarbeets and
weeds. Weed Sci. 24(6):619-626.

Flore, J. A. and M. J. Bukovac. 1974. Pesticide effects on the
plant cuticle: 1. Response of Brassica oleracea L. to EPTC as
indexed by epicuticular wax production. Proc. Amer. Soc. Hort.
Sci. 99(1):34-37.

 

Gentner, W. A. 1966. The influence of EPTC on external foliage wax
development. Weeds 14:27-31.

Juniper, B. E. 1957. The effect of pre-emergent treatment of peas
with trichloroacetic acid on the submicroscopic structure of the
leaf surface. New Phytol. 58:1—5.

Kolattukudy, P. E. 1965. Biosynthesis of wax in Brassica oleracea.
Biochemistry 4:1844-1855.

 

Leavitt, J. R. C., D. N. Duncan, 0. Penner and W. F. Meggitt. 1978.
Inhibition of epicuticular wax deposition on cabbage by ethofume-
sate. Plant Physiol. (In Press).

Pfeiffer, R. K., 0. R. Dewey, and R. T. Brunskill. 1959. Further
investigation of the effect of pre-emergence treatment with
trichloroacetic dichloropropionic acids on the subsequent reaction
of plants to other herbicidal sprays. Proc. 4th Int. Cong. Crop
Protection 1:523-525. .

Putnam, Alan R. and Donald Penner. 1974. Pesticide interactions in
higher plants. Residue Reviews 50:73-110.

28

Table 1. Influence of preemergence herbicide treatment on the activity
of ethofumesate plus desmedipham combination applied post-
emergence in field studies at 1.68 + 0.84 kg/ha during 1976

 

 

 

 

 

and 1977.
Treatment Growth Root
3 b reduction yield
Preemergence Postemergence” (%) (ton/ha)
- - 0 3C 54 a
- + 4 a 54 a
Pyrazon + TCA - l a 52 a
Pyrazon + TCA + 18 b 50 a
Ethofumesate + TCA - 3 a 52 a
Ethofumesate + TCA + 32 c 47 a
Main effect for years: 1976 6.4 a 54 a
1977 13.1 a 49 a
Main effect for locations: I 8.9 a 52 a
II 11.0 a 50 a

 

a . . . . .
Preemergence herb1c1de rate varied between two locat1ons depending on

soil type and

bPostemergence
sugarbeets in

cValues within
ferent at the

organic content.

treatment of ethofumesate plus desmedipham applied to
the two to four-leaf stage.

columns with the same letter are not significantly dif-
% level using Duncan's multiple range test.

29

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ecu .wom womwomsoo ocooox-oom mm-u .wfio womfihmsoo ocmxfim mm-u esp .Hoepeoo one you .umou emcee ofiqflufise
m.:mocza wcfim: Ho>oH wm map on acouommwp xflucmofimflcmflm we: own houuog oEmm ecu cow: maesfioo awsufiz mosfim>m

 

 

 

a mm a so a me Nh.o+em.m <oe + conwxa

a mmH m m a m NA.©+4N.N <eo + ouamoesmospm

m aw n mm a He mn.o <oe

m mes 0 mm 0 4o om.m conoxa

a ems m Nu m a em.m mommmesmogom

mpoumo Axe: camconmcofl weepoxuoom mm-u ocmxflm mmuu amc\mxv ucoEumpo
wHoppcoo mo w oumm

 

.040 »n pocfiEhopop mucocoaeoo xmz poonhmmsm

hemme :o “coaumohu opflownho; oocompoEoohm mo woommm .m ofinmb

 

30

Table 3. Cuticular transpiration of sugarbeet leaves in response to

preemergence herbicide treatment.

 

 

Rate Transpiration
Treatment (kg/ha) (% H20 loss/hr)
Control - 4.3 a
CHCls—washed control — 51.5 e
Ethofumesate 2.24 15.9 c
Pyrazon 3.36 3.8 3
TCA 6.72 10.0 b
Ethofumesate + TCA 2.24+6.72 27.9 d
Pyrazon + TCA 3.36+6.72 12.1 bc

 

aValues with the same letter or letters are not significantly different

at the 5% level using Duncan's multiple range test.

31

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32

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vH

33

Figure 1. Photograph of upper surface of first two true sugarbeet
leaves. Control (1) and ethofumesate-treated preemergence
at 2.24 kg/ha (r).

34

 

35

Figure 2. Scanning electron micrographs of the upper surface of fresh
sugarbeet leaves from control (above) and ethofumesate-
treated (below) plants, 1000x.

36

 

CHAPTER 3

THE BASIS FOR SELECTIVITY OF ROOT-APPLIED ETHOFUMESATE

IN SUGARBEET AND THREE WEED SPECIES
ABSTRACT
The absorption, translocation, and metabolism of 14C-ethofumesate

(2-ethoxy-2,3-dihydro-3,3-dimethyl-5-benzofuranyl methanesulphonate) in

sugarbeet (Beta vulgaris L.), common ragweed (Ambrosia artemisfolia L.),

 

 

redroot pigweed (Amaranthus retroflexus L.), and common lambsquarter

 

(Chenopodium album L.) were studied as possible bases for selectivity of

 

preemergence applied ethofumesate. The seedlings were grown in the green—
house in nutrient culture and transferred to nutrient solution contain-
ing 14C-ethofumesate for exposures of l, 3, or 7 days. The sensitive
pigweed and lambsquarter plants translocated more 14C-ethofumesate to

the leaf tissue than the tolerant sugarbeet and ragweed. The 14C was
more highly concentrated in the root portion of sugarbeet and ragweed.
Movement and accumulation increased with time of exposure for all species.
Stem tissue of both sugarbeet and ragweed contained a greater percentage
of non-extractable residue than pigweed or lambsquarter. There were con-
siderable species differences in the 14C-metabolites formed after 1, 3,
and 7 days exposure to 14C-ethofumesate. The rapid metabolism of

ethofumesate by the tolerant sugarbeet and ragweed, particularly in the

leaf tissue, appeared related to tolerance.

37

38

INTRODUCTION

Ethofumesate is a new selective herbicide recently registered1 by
the Environmental Protection Agency for preplant incorporation and pre-
emergence control of some annual broadleaf and grass weeds in sugarbeet
(5,6). Redroot pigweed and common lambsquarter are highly susceptible to
preemergence applications of ethofumesate. However, common ragweed is
equal to the sugarbeet in tolerance (2,3). No information is available
on the mechanism for this difference in tolerance.

The purpose of this study was to determine the basis for the selecti-
vity of ethofumesate between sugarbeet, redroot pigweed, common lambsquarter,

and common ragweed by comparing root absorption, translocation, and metabo-

lism.

MATERIALS AND METHODS

'USH 20' sugarbeet, common ragweed, redroot pigweed, and common
lambsquarter were germinated in vermiculite in the greenhouse and trans-
ferred to l/2-strength Hoagland's nutrient solution (4) in foil wrapped,
250-ml plastic pots with sponge supports. When plants were in the cotyle-
don stage they were placed in growth chambers with a 16 hr day at 25 C.
Light intensity at plant level was 24 to 27 klux provided by a mixture
of fluorescent and incandescent lamps. The 14C-ethofumesate was uniformly
labeled in the benofuranyl ring with a specific activity of 1.34 uCi/umole.

.A stock solution was made by dissolving the ethofumesate in ethanol and

 

1Registered as NortronR, a trademark of Fisons Limited.

39

diluting it with formulated herbicide in distilled water. The ethanol
was evaporated with nitrogen before application. Data reported are the
means of two experiments with four replications each. After a 7 day
period of acclimatization and a selection for uniformity, plants were
transferred to foil-lined, 50 ml graduated tubes (one per tube) containing
4 x 10.6 M ethofumesate and nutrient solution. Transpiration was moni-
tored over time to determine if species differences existed between water
uptake and herbicide uptake. The tubes were replenished daily with the
ethofumesate-containing nutrient solution. One ml aliquots were taken
to chromatographically determine the % purity of the parent ethofumesate
at each time interval by thin layer chromatography (TLC).

Four replicate plants were harvested after 1, 3, and 7 days exposure.
One plant was used for radioautography and three for quantitative 14C
determination. At harvest, the roots were rinsed in three consecutive
water baths and blotted dry. The plants were placed on dry ice, freeze-
dried, and then radioautographed or divided into leaf, stem, and root
sections for dry weight determination and extraction. Plant parts were
homogenized twice in 50 ml 80% ethanol with a Sorvall Omni-Mixer. After
grinding, the plant extracts were filtered through Whatman No. 1 filter
paper under vacuum and rinsed with ethanol. The ethanol-insoluble resi-
due was collected for dry weight determination and combusted to quantita-
tively determine the ethanol-insoluble 14C material. A Packard 306 Tri-
Carb Sample Oxidizer was used to combust the tissue. Released 14CO2 was
trapped with 12 ml Carbo-SorbR and further diluted with 10 ml PermaflourR V
liquid scintillation solution. The ethanol-soluble filtrate was evaporated

in vacuo and the remaining aqueous residue partitioned twice with 40 ml

dichloromethane. The dichloromethane phase was sampled for radioactivity

.L ' L t
. l x V
. 11 Du
1 - ”.3

«\c

40

and chromatographic determination of 14C-ethofumesate and 14C-metabolites.
The aqueous layer was boiled for 2 hr with 12 N HCL to hydrolize any con-
jugates. After another extraction and partitioning with dichloromethane,
aliquots were taken of both aqueous and dichloromethane layers for addi-
tional radioassay and chromatography of metabolites released from conju-
gation. All aliquots were radioassayed by liquid scintillation spectro-
metry and 100 pl of each fraction spotted on 250 umeter think silica gel
G thin layer chromatography plates. The plates were radioautographed and
the l4C-labeled spots on the plate removed and radioassayed. All radio-

assay data was corrected for background with efficiency determined by

channels ratio method.
RESULTS AND DISCUSSION

During the first 3 days of exposure, ragweed and lambsquarter ab-
sorbed significantly more 14C-ethofumesate from the nutrient solution
than sugarbeet (Table l). Sugarbeet, an ethofumesate tolerant species,
absorbed low amounts of 14C. The highly susceptible redroot pigweed
absorbed a similar amount during this time. The greatest amount of 14C
was found in the highly tolerant common ragweed while the susceptible
lambsquarter ranked intermediate in 14C uptake. After 7 days there were
no differences in absorption among species. Therefore, these results
indicate that differences in root absorption of l4C-ethofumesate do not
explain differences in ethofumesate selectivity between these two toler-
ant and two susceptible species.

The distribution pattern of 14C-ethofumesate indicates rapid trans-

location of 14C to the leaf portion of the susceptible redroot pigweed

41

and lambsquarter species (Table 2). The 14C was more highly concentrated
in the root portion of the tolerant sugarbeet and common ragweed species.
The movement and accumulation increased with time for all species (Table

2 and Figures 1 to 4). It has been reported that foliar treatments of
ethofumesate act to inhibit photosynthesis and respiration in redroot pig-
weed (2). Conceivably, greater transport of 14C-ethofumesate to the leaf
portion of the susceptible redroot pigweed and lambsquarter could, in
part, account for response differences between susceptible and tolerant
plants.

Analysis of the ethanol-insoluble (non-extractable) 14C-labeled
residue revealed a significant interaction among species, plant component,
and length of exposure time (Table 3). Both sugarbeet and ragweed con-
tained a greater percentage of radioactivity in the ethanol-insoluble
fraction of the stem than either the leaf or root segments. The stem
portibn of the tolerant species was higher in radioactivity than that of
the two susceptible species. This response was particularly evident for
ragweed at all times for sugarbeet after 3 days exposure. Thus, the rapid
14C uptake by ragweed was counteracted by metabolism or binding of 14C
into the ethanol-insoluble fraction of the stem and leaf.

TLC analysis of crude ethanol/dichloromethane extracts of plants
following root treatment with 14C-ethofumesate provides evidence for
metabolism of ethofumesate by all species (Tables 4, 5, and 6). After 7
days exposure, ethofumesate metabolism in sugarbeet and ragweed differed
markedly from that of redroot pigweed and lambsquarter. Only a small
percentage of 14C was detected in the dichloromethane-soluble fraction,
particularly after 7 days exposure, in sugarbeet compared to the other

three species (Table 5). The majority of the 14C was possibly conjugated

with '

 

ble f:
ethof;
and r,
(21% x
and r.
expos;
1°C TE
susce;

Specia

be dep
A1thou

have d

 

 

 

sugarb
Plant

SPGCie
Sate 1
thn ‘
Sate j
“Ere 1
the o}

ethOf]

42

with water-soluble plant constituents. Acid hydrolysis of the water-solu-
ble fraction of leaf components released decreasing amounts of parent
ethofumesate with increased time of exposure for sugarbeet (85% to 11%)
and ragweed (69% to 36%). The opposite was observed for leaves of pigweed
(21% to 79%) and lambsquarter (40% to 75%) (Table 7). For both sugarbeet
and ragweed, the metabolism of parent ethofumesate increased with time of
exposure, particularly in the leaf segment (Table 6). The percentage of
14C remaining as unmetabolized ethofumesate was significantly greater in
susceptible redroot pigweed and lambsquarter than for the two tolerant
species. This difference was specially evident after 7 days exposure.

Differences in phytotoxicity of root-applied ethofumesate appears to
be dependent on both metabolism and translocation within the plant species.
Although both sugarbeet and ragweed are resistant species, they appear to
have differing mechanisms for detoxifying the parent ethofumesate. In
sugarbeet there was rapid conjugation with dichloromethane—insolub1e
plant constituents and relatively slower absorption than in the susceptible
species. And after 7 days, hydrolysis revealed only 11% parent ethofume-
sate remaining in the leaf portion of the dichloromethane-soluble frac-
tion (Table 7). Conversely, ragweed rapidly converted parent ethofume-
sate into dichloromethane-soluble metabolites. Few water-soluble products
were formed. Extremely slow metabolism in all plant parts contributed to
the observed susceptibility of redroot pigweed and lambsquarter to

ethofumesate.

43

LITERATURE CITED

Duncan, 0. N., W. F. Meggitt, and D. Penner. 1977. A mode of
action of ethofumesate. Weed Sci. Soc. Amer. Abstr. p. 84.

Duncan, D. N., W. F. Meggitt, and R. C. Bond. 1977. General weed
control evaluations in Michigan sugarbeets. Research Report N.
Centr. Weed Contr. Conf. 34:139.

Duncan, David N., W. F. Meggitt, and R. C. Bond. 1976. Weed
control evaluations at different stages of growth in sugarbeets.
Research Report N. Cent. Weed Contr. Conf. 33:170.

Hoagland, D. R. and D. I. Arnon. 1950. The water culture method
for growing plants without soil. California Agr. Exp. Sta. Circ.
347: 32 pp.

Holmes, H. M., R. K. Pfeiffer, and W. Griffiths. 1974. Pre-emergence
and post—emergence use of ethofumesate in sugarbeet. Proc. 12th
British Weed Cont. Conf. 493-501.

Sharpe, N., O. Segarceanu, L. Ciorlaus, I. Popovici, I. Clotan, and
C. Nagy. 1974. The efficiency of herbicides based on pyrazon,
ethofumesate, lenacil, and phenmedipham, used alone or in combi-
nation, in sugarbeet grown under Romanian conditions. Proc. 12th
British Weed Cont. Conf. 477-483.

44

Table l. Uptake of 14C-ethofumesate by sugarbeet and three weed species

grown in nutrient solution containing 4 x 10'6

M ethofumesate.

 

Time of exposure

 

 

 

1 day 3 day 7 day
Species (umole/mg whole plant dry wt)
Sugarbeet 25 aa 41 ab 83 de
Ragweed 69 cd 90 e 88 de
Pigweed 38 ab 56 be 81 de
Lambsquarter 49 bc 67 cd 71 cde
aMeans within columns and rows having identical letters are not signifi-

cantly different at the 5% level using Duncan's multiple range test.

Tabl:

Spec:

Sugar

Pigwe-

LambSL

 

a
Means
Cant}

45

Table 2. Distribution of 14C in sugarbeet and three weed species grown
in nutrient solution containing 4 x 10'6 M ethofumesate after
1, 3, and 7 days exposure.

 

Time of exposure

 

 

Plant 1 day 3 day 7 day
Species component (umole/mg dry wt)
Sugarbeet Leaf 29 aba 47 b—e 77 h-k
Stem 21 a 20 a 76 g-k
Root 21 a 33 ab 103 mn
Ragweed Leaf 45 bcd 67 f-i 69 f-j
Stem 100 lmn 88 klm 83 i-l
Root 129 o 165 p 169 p
Pigweed Leaf 87 j-m 78 h-k 114 no
Stem 6S e-i 58 d-g 83 i-f
Root 30 ab 54 c-f 53 c-f
Lambsquarter Leaf S6 c-f 53 c-f 93 klm
Stem 45 bcd 34 ab 67 f-i
Root 22 a 38 abc 61 d-h

 

aMeans within columns and rows having identical letters are not signifi-
cantly different at the 5% level using Duncan's multiple range test.

46

Table 3. Percent non-extractable radioactivity after 14C-ethofumesate
absorption for leaf, stem, and root components of 4 species
after 1, 3, and 7 days exposure.

 

 

 

Length of Plant component
exposure Leaf Stem Root
Species (days) (%) (%) (%)
Sugarbeet l 18 a—ea 18 a-e 6 ab
3 24 c—g 41 hi 17 a-e
7 38 gh 66 k 16 a-e
Ragweed l 8 ab 35 fgh 5 a
3 28 d-h 60 jk 8 ab
7 S3 ij 70 k 14 a-d
Pigweed l 16 a-e 20 b-e 8 ab
3 29 e-h 18 a-e 16 a—e
7 37 gh l8 a-e l6 a-e
Lambsquarter l 14 abc 34 fgh 13 abc
3 23 c-f 33 fgh l6 a-e
7 37 gh 32 e-h 25 c-g

 

aMeans within columns and rows having identical letters are not signifi-
cantly different at the 5% level using Duncan's multiple range test.

47

 

 

 

 

 

 

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48

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49

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50

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51

Figure 1. Translocation of 14C-ethofumesate in sugarbeet. The radio-
autograph (A) after 1, 3, and 7 days exposure to treatment
(left to right) and corresponding plant specimen (B).

52

 

53

Figure 2. Translocation of 14C-ethofumesate in ragweed. The radio—
autograph (A) after 1, 3, and 7 days exposure to treatment
(left to right) and corresponding plant specimen (B).

S4

 

55

Figure 3. Translocation of 14C-ethofumesate in redroot pigweed. The
radioautograph (A) after 1, 3, and 7 days exposure to treat-
ment (left to right) and corresponding plant specimen (B).

 

57

Figure 4. The translocation of l4C-ethofumesate in lambsquarter. The
radioautograph (A) after 1, 3, and 7 days exposure to treat-
ment (left to right) and corresponding plant specimen (B).

CHAPTER 4

PHYSIOLOGICAL BASES OF SUGARBEET (BETA VULGARIS) TOLERANCE TO

 

FOLIAR APPLICATION OF ETHOFUMESATE

ABSTRACT

Absorption, translocation, and metabolism of foliar-applied ethofume-
sate (2-ethoxy-2,3—dihydro-3,3-dimethy1-S-benzofuranyl methanesulphonate)
were studied to explain field observations showing differences in suscepti-

bility among sugarbeet (Beta vulgaris L.), common ragweed (Ambrosia

 

artemisiifolia L.), redroot pigweed (Amaranthus retroflexus L.), and com-

 

 

mon lambsquarter (Chenopodium album L.). In laboratory studies seedlings

 

of the highly susceptible species, pigweed and lambsquarter, absorbed
greater amounts of 14C-ethofumesate from foliar application than the
moderately susceptible ragweed and tolerant sugarbeet. Sugarbeet trans—
located very little 14C from treated foliage to untreated plant tissue.

All weed species translocated 14C-ethofumesate to untreated leaf tissue
when 14C-ethofumesate was applied to seedlings at the/two-leaf stage.
Ethofumesate was moved basipetally to the stem and root components of two-
leaf pigweed and lambsquarter seedlings. High percentages of 14C complexed
with polar constituents in sugarbeet seedlings. The amount of metabolites
recovered in the non-polar fraction depended on the stage of plant growth.

Total photosynthesis and respiration in pigweed was inhibited 4 hr after

foliar application and did not recover. CO2 uptake and evolution were

59

60

also inhibited in sugarbeet leaves but they recovered rapidly, depending
on age of plant at treatment. The stage of plant development was the key
factor in determining species response to foliar treatments of ethofume-
sate in terms of absorption, metabolism, and total photosynthesis and

respiration.

INTRODUCTION

Successful weed control in sugarbeet or any crop using foliar-applied
herbicides depends on the absorption and translocation of the biologically
active compound to the site of phytotoxic action in sufficient quantities
to kill the weed before metabolism can detoxify the compound. For the
chemical to be selective, the crop must either limit uptake or movement
from the treated areas, or must enhance deactivation of the potential
herbicide.

Ethofumesate is a potential postemergence herbicide for the selec—
tive control of broadleaf weeds in sugarbeet and is currently under experi~
mental permit for this purpose (3,7,8). Redroot pigweed and lambsquarter
are highly susceptible, and common ragweed moderately susceptible to
foliar applications of ethofumesate, depending on stage of growth at
treatment (3).

The purpose of this study was to determine the contribution of foliar
absorption, translocation, and metabolism to ethofumesate toxicity and
selectivity at the two-, four-, and six-leaf stages of plant development
of sugarbeet, redroot pigweed, ragweed, and lambsquarter. C02 uptake and
evolution were also studied for sugarbeet and redroot pigweed at two

growth stages.

61

MATERIALS AND METHODS

1 . . .
4C-absorption, translocation, and metabolism. Sugarbeet, common

 

ragweed, redroot pigweed, and lambsquarter were germinated in vermiculite
in the greenhouse and transferred to 1/2 strength Hoagland's nutrient
solution in foil-wrapped, 250 ml plastic pots with sponge supports.
Plants were grown to the desired stage of development (two-, four-, or
six-leaf), selected for uniformity, and placed in a growth chamber at 25 C
and 27 klux with a spec. act. = 1.35 pCi/pmole) was dissolved in ethanol
and additional formulated herbicide added to obtain a concentration approxi-
mating the use rate for foliar application, 1.69 kg/ha. A 10 p1 drop
(0.1 pci) of herbicide was placed in the middle of the upper leaf surface
of one of the first two true leaves of each plant species. The leaf was
held horizontal until the drop dried, after which the plants were moved
back to the growth chamber. Plants for the absorption portion of the
study were harvested 3 and 24 hours after treatment. The treated leaf
of each plant was rinsed with 20 ml of 50% ethanol to remove any remain-
ing herbicide. The plants were freeze-dried and dissected into treated
leaf, other leaves, stem, and root segments. All samples were combusted

4

with a Packard 306 Tri-Carb Oxidizer to determine the quantity of 1 C in

each plant part. Released 14CO was trapped with 12 ml Carbo-SorbR and

2
further diluted with 10 m1 PermaflourR V liquid scintillation solution.
The vials containing the sample were radioassayed by liquid scintillation
spectrometry and the data expressed as pg ethofumesate absorbed per g dry
weight. The treatments were replicated four times in a randomized split

block design.

Two replications for radioautography and three for quantitative

62

determination were harvested 1 and 5 days after treatment for the trans-
location and metabolism portions of the study. All plants were cultured
and treated as previously described. After washing the treated leaf with
50% ethanol, plants were frozen on dry ice, freeze-dried, and either
mounted for radioautography (l) or the treated leaf separated from the
rest of the plant for dry weight determination and extraction of the two
portions. Plant parts were homogenized twice in 50 ml 80% ethanol with
a Sorvall Omni-Mixer. After grinding, the plant extracts were filtered
through Whatman No. 1 filter paper under vacuum and rinsed with ethanol.
The ethanol-insoluble residue was collected for dry weight and combusted
for 14C determination. The ethanol-soluble filtrate was evaporated in
vacuo and the remaining aqueous residue partitioned twice with 40 ml
dichloromethane. Both phases (dichloromethane- and water-soluble) were
sampled for radioactivity and chromatographic determination of free 14C—
ethofumesate and l4C-metabolites. All aliquots were separated on 250
pmeter think silica gel G thin layer chromatography plates. The plates
were radioautographed and the 14C-labeled spots on the plate removed and
radioassayed. All radioassay data was corrected for background and

efficiency determined by channels ratio method.

Photosynthesis study. Four sugarbeet or pigweed plants per 946 ml

 

waxes cups were grown in soil until the plants had reached two different
stages of development, two- or six-leaf. The plants were grown in the
greenhouse supplemented with artificial lighting to provide a 16 hr day.
Temperature ranged from a medium of 20°C at night to a maximum of 33 C
during the day. Fourty-eight hours prior to measurement plants were
transferred to a growth chamber at 25 C in light of 27 klux with 14 hours

of day length. Plants received 28 hr light during this period.

63

Photosynthesis and respiration measurements were made by placing the cups,
one at a time, in a sealed, clear plexi-glass test chamber located in the
same growth chamber. The chamber was attached to a Beckman Model IR 215
C02 infrared gas analyzer. Compressed air for the open flow system was
passed through the chamber at a rate of 500 cc per minute. Measurements
were made at 0, 4, 24, 48, and 96 hours after the foliar treatments with
ethofumesate (2.24 kg/ha) and for comparative purposes, desmedipham

(ethyl m-hydroxycarbanilate carbanilate) (0.82 kg/ha). Plants were sprayed
in 285 l/ha at 2.11 kg/cm pressure. Leaf area was determined with an
automatic area meter (Lambda Instruments).

All data presented are the means of two experiments.
RESULTS AND DISCUSSION

Absorption of foliar-applied 14C-ethofumesate by sugarbeet and three
weed species was dependent on stage of growth on treatment and time of
exposure to the chemical (Table 1). The two susceptible species, lambs-
quarter and particularly pigweed, absorbed more ethofumesate at both the
two- and four-leaf stages of growth than sugarbeet. After 24 hr exposure
the moderately susceptible ragweed absorbed more than the tolerant sugar-
beet, the differential widening with increasing plant age. A previous
report indicated no increase in absorption by sugarbeet after 3 hr expo-
sure to ethofumesate (6). A significant increase in absorption was ob-
served with increased exposure (24 hr) to ethofumesate applied to two-leaf
sugarbeet and the three weed species. This differende was not observed
for sugarbeet at either the four- or six-leaf stages of growth.

Translocation also appeared to be a significant factor in selectivity.

64

Regardless of stage of growth at treatment, no significant accumulation
of 14C was observed in the untreated plant segments of sugarbeet 24 hr
after foliar application (Figure l and Table 2). However, all weed
species translocated 14C—ethofumesate to untreated leaf tissue (acropetal
movement) when applications of ethofumesate were made at the two—leaf
stage of development (Figures 2 to 4 and Table 2). Basipetal movement
of 14C to the stem and root components was detected only in two- and four-
leaf pigweed andtwo-leaf lambsquarter species. A similar distribution
pattern was observed 3 hr after application. The absorption and trans-
location data appeared highly consistent with the field information on
selectivity of foliar-applied ethofumesate to sugarbeet and associated
weed species at the three leaf stages of growth (2).

Few species differences were observed in the amount of 14C- etho-
fumesate (dichloromethane-soluble) recovered at any one stage of growth
or time of exposure (Tables 3, 4, and 5). After 5 days of exposure to
ethofumesate applied at the four- and six-leaf stages, a significant
increase in 14C-metabolites was detected in all species, but especially
in the weed species at the six-leaf stage. However, as much as 91% of
the total extractable 14C in sugarbeet was found in the water-soluble
residue. This percentage increased markedly from plants treated at the
two-leaf (59.9% after 5 days) to those treated at the four-leaf stage
(91.2%), with no additional increase detected in plants treated at the
six-leaf stage (90.3%). Complexing of parent ethofumesate and metabolites
with water-soluble plant constituents in sugarbeet leaves was a signifi-
cant factor in the detoxication process of root-applied l4C-ethofumesate

(4). Thus, the same mechanism appeared likely with foliar-applied etho-

fumesate on sugarbeet, particularly at the four- and six-leaf stages of

65

growth. Inactivation of ethofumesate by the weed species involved, to a
greater extent, breakdown of ethofumesate to organic-soluble metabolites.
The amount of dichloromethane-soluble l4C found in sugarbeet treated at
the four- and six-leaf stages was extremely small considering less than
10% of the total was recovered in this fraction. For both stages, less
than 40% was detected as metabolite. Therefore, the nature of the meta-
bolism appears to be different between the tolerant sugarbeet and the
three weed species.

Ethofumesate applications reduced the CO uptake of sugarbeet and

2
pigweed within 4 hr after treatment at both the two- and six-leaf stages
(Table 6). Total photosynthesis in pigweed did not recover within the
96 hr observation period for either growth stage. The six-leaf sugar-
beet recovered rapidly, but 96 hr were required to detect significant
recovery in sugarbeet treated at the two-leaf stage. Dark respiration
of ethofumesate-treated sugarbeet was reduced when applied to the two-

leaf but not the six-leaf stage of growth. For pigweed, CO evolution

2
was reduced regardless of stage of growth at treatment. Regarding recovery,
dark respiration paralleled photosynthetic activity. Desmedipham, reported
to be an effective photosynthetic and respiratory inhibitor (7), was in-
cluded in this study for comparison. This data confirms previous results
obtained with foliar-applied desmedipham and, in terms of selectivity,
indicates similarity to ethofumesate.

Ethofumesate appears to be a rapid inhibitor of reSpiration and
photosynthesis. The inhibition followed by recovery of sugarbeet, but
not pigweed, indicates that metabolism of ethofumesate is involved in

selectivity. At the two-leaf stage of sugarbeet where photosynthetic re-

covery was not apparent for 4 days (Table 6), metabolism of parent

66

ethofumesate was also slow (Table 3). However, recovery of CO2 uptake
was rapid (within 24 hr) at the six-leaf stage (Table 6) where 85% of
extractable 14C was complexed with polar plant constituents after 24 hr
exposure to 14C-ethofumesate (Table 5).

Several factors may have contributed to the observed selectivity to
foliar applications of ethofumesate. For the youngest of seedlings, rapid
and continued absorption, extensive accumulation in untreated plant com-
ponents, particularly leaves, slow metabolism, and inhibited photosynthe-
sis all appeared to play an active role in susceptibility of redroot pig-
weed and lambsquarter to foliar applications of ethofumesate. The stage
of plant development was the primary factor in determining species re-
sponse to ethofumesate treatment relative to absorption, translocation,

metabolism, and CO2 uptake and evolution.

67

LITERATURE CITED

Crafts, A. S. and S. Yamaguchi. 1964. The autoradiography of
plant material. Calif. Agr. Exp. Sta. Ext. Serv. Manual 35,
143 pp. ‘

Duncan, 0. N., W. F. Meggitt, and R. C. Bond. 1976. .Weed control
evaluations at different stages of growth in sugarbeet. Research
Report N. Cent. Weed Contr. Conf. 33:170.

Duncan, 0. N., W. F. Meggitt, and D. Penner. 1977. A mode of
action of ethofumesate. Weed Sci. Soc. Amer. Abstr. p. 84.

Duncan, 0. N., W. F. Meggitt, and D. Penner. 1978. The basis for
selectivity of root-applied ethofumesate in sugarbeet and three
weed species. Weed Sci. (Submitted).

Eshel, Y., E. E. Schweizer, and R. L. Zimdahl. 1976. Sugarbeet
tolerance of post-emergence applications of desmedipham and
ethofumesate. Weed Res. 16:249-254.

Eshel, Y., R. L. Zimdahl, and E. E. Schweizer. 1976. Basis for
interactions of ethofumesate and desmedipham on sugarbeets and
weeds. Weed Sci. 24:619-626.

Hendrick, L. W., W. F. Meggitt, and D. Penner. 1974. Basis for
selectivity of phenmedipham and desmedipham on wild mustard,
redroot pigweed, and sugarbeet. Weed Sci. 22:179-184.

Holmes, H. M., R. K. Pfeiffer, and W. Griffiths. 1974. Pre-
emergence and post-emergence use of ethofumesate in sugarbeet.
Proc. 12th British Weed Cont. Conf. 493-501.

Table 1. Absorption of foliar applied 14

68

C-ethofumesate by sugarbeet and

three weed species as influenced by stage of growth at appli-
cation and time of exposure.

 

 

 

Exposure Stage of growth at treatment
time two-leaf four-leaf six-leaf
Species (hr) (pg/g dry weight)
Sugarbeet 3 52.4 b-ea 2.4 a l 0 a
24 151.6 gh 13.5 abc 7.6 ab
Ragweed 3 196.0 h 50.2 a-e 55.5 b-e
24 346.0 j 67.7 de 61.1 cde
Pigweed 3 398.1 k 293.6 i 19.2 a-d
24 936.9 m 558.7 1 55.2 b-e
Lambsquarter 3 444.9 k 74 4 ef 10 l ab
24 540.4 1 301.3 ij 121.0 fg

 

aMeans within columns and rows having identical letters are not signifi-
cantly different at the 5% level using Duncan's multiple range test.

69

Table 2. Distribution of 14C-ethofumesate 24 hr after foliar application
to sugarbeet and three weed species as influenced by stage of
growth at application.

 

Plantpparts

 

 

Stage of Treated other

growth leaf leaves Stem Root

Species (leaves) (pg/g dry weight)
Sugarbeet 2 138.2 b8 8.0 a 3.5 a 2.2 a
4 ll 9 a 0 2 a 0 8 a 0 7 a
6 6 9 a 0 2 a 0 2 a 0 3 a
Ragweed 2 228.8 c 87.5 b 17.4 b 14.0 a
4 50.9 a 15.8 a 1.0 a 1.9 a
6 50.1 a 9.0 a 1.3 a 1.8 a
Pigweed 2 373.0 e 368.8 d 85.6 b 110.0 b
4 320.5 d 189.2 c 30.3 a 19.0 a
6 28.5 a 12.8 a 13.4 a 2.0 a
Lambsquarter 2 383.0 e 119.5 b 21.0 a 17.6 a
4 247.1 c 31.0 a 11.5 a 12.6 a

 

aMeans within columns having identical letters are not significantly dif-
ferent at the 5% level using Duncan's multiple range test.

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.cuzoem mo eweum weeH-me ecu ue OeHoemm ueeHm Neom ou euemessmocuesu 0eHHmme ueHHom mo EmHHoceuez .m eHceH

eH

73

Table 6. Percent of initial total photosynthesis of two species influ-
enced by postemergence herbicide application and stage of
growth at treatment.

 

 

 

Stage of Time after treatment (hr)
growth Herbicide 4 24 48 96
(leaves) Species (% of initial photosynthetic rate)
2 Ethofumesate b a
Sugarbeet 52* fgh 34 c-f 30 b-e 67* hi
Redroot pigweed 54* ghi 20 a-e 18 a-d 22* a-e
Desmedipham
Sugarbeet 31* b—e 63 hi 66 hi 126* m
Redroot pigweed 18* a-d 9 a 7 a 14* ab
6 Ethofumesate ,
Sugarbeet 64* hi 98 kl 93 k1 108 klm
Redroot pigweed 73* ij 39 efg 24 a-e 15* abc
Desmedipham
Sugarbeet 62* hi 64 hi 90 jk 112 lm
Redroot pigweed 37* d-g 8 a 7 a 6* a

 

aMeans followed by the same letters are not significantly different at
the 5% level using Duncan's multiple range test.

bAsterisks indicate significance between the amount of photosynthesis
prior to and 4 hr or 96 hr after herbicide treatment using students
"T" test.

74

Table 7. Percent of initial dark respiration of two species as influenced
by postemergence herbicide application and stage of growth at
treatment.

 

 

 

Stage of Time after treatment (hr)
growth Herbicide 4 24 48 96
(leaves) Species (% of initial respiration rate)
2 Ethofumesate b a
Sugarbeet 42* def 31 bcd 38 cde 67* ghi
Redroot pigweed 75* hij 22 abc 9 a 11* a
Desmedipham
Sugarbeet 48* d-g 64 ghi 90 jk 100* kl
Redroot pigweed 39* c-f 22 abc 15 ab 15* ab
6 Ethofumesate
Sugarbeet 80 ij 119 lm 140 n 143* n
Redroot pigweed 78* ij 67 ghi 42 def 42* def
Desmedipham
Sugarbeet 64* ghi 62 ghi 89 jk 112 lm
Redroot pigweed 91 jk 88 jk 55 efg 58* fgh

 

aMeans followed by the same letters are not significantly different at
the 5% level using Duncan's multiple range test.

bAsterisks indicate significance between the amount of photosynthesis
prior to and 4 hr or 96 hr after herbicide treatment using students
"T" test.

75

Figure 1. Translocation of 14C—ethofumesate in sugarbeet. The radio-
autographs (A) at the two-, four-, and six-leaf stages of

growth (left to right) and corresponding plant specimens (B).
Arrows indicate treated leaves.

76

 

77

Figure 2. Translocation of l4C—ethofumesate in common ragweed. The
radioautographs (A) at the two-, four-, and six—leaf stages
of growth (left to right) and corresponding plant specimens
(B). Arrows indicate treated leaves.

79

Figure 3. Translocation of 14C—ethofumesate in redroot pigweed. The
radioautographs (A) at the two-, four-, and six-leaf stages
of growth (left to right) and corresponding plant specimens
(B). Arrows indicate treated leaves.

8O

 

81

Figure 4. Translocation of 14C—ethofumesate in common lambsquarter. The
radioautographs (A) at the two-, four-, and six-leaf stages of

growth (left to right) and corresponding plant specimens (B).
Arrows indicate treated leaves.

 

CHAPTER 5

SUMMARY AND CONCLUSIONS

Studies were conducted in the field to evaluate the various factors
influencing ethofumesate and other postemergence herbicide treatments on
sugarbeet. Greenhouse and laboratory studies were initiated to determine
the basis for the observed interaction of sequential herbicide combina—
tions in the field, and to study the physiological bases for sugarbeet
tolerance to soil- and foliar-applied ethofumesate.

Preemergence application of the combination of ethofumesate plus TCA
caused greater suppression than pyrazon plus TCA when followed by a post-
emergence herbicide treatment to field grown sugarbeets. Additionally,
sugarbeet tolerance and weed control depended largely on the stage of
plant growth at time of foliar application. Foliar treatment at the two-
to four-leaf stage provided minimal sugarbeet injury with optimal weed
control results. Depending on temperature and light intensity subsequent
to foliar application of herbicides, time-of—day at application may also
play an important role in determining the degree of selectivity to
ethofumesate. On a cloudless day where the ambient temperature reached
32 C, mid-afternoon treatment combinations were less phytotoxic and pro-
vided equal or greater weed control compared to morning or evening treat-
ments.

Exposure of sugarbeet to ethofumesate and TCA decreased the

83

84

epicuticular wax deposition on the leaf surfaces. Greater absorption of
14C-herbicides was observed in plants that received preemergence treat-
ments of ethofumesate and TCA as compared to pyrazon or a control.
Therefore, the basis for the interaction of sequential herbicide combi-
nations was increased absorption of foliar applications due to reduction
in epicuticular leaf wax deposition from soil-applied herbicides.

The basis for selectivity of ethofumesate in sugarbeet and associ-
ated weed species varied with manner of application. For root-applied
ethofumesate, slow translocation to the leaves and rapid metabolism with-
in sugarbeet and ragweed compared to pigweed and lambsquarter appeared
related to species differences in phytotoxicity. Absorption, transloca-
tion, and metabolism all contributed to the observed selectivity of
foliar applications of ethofumesate. As with the field study, response
to foliar treatment varied primarily with stage of plant development.

For the youngest seedlings, rapid and continued absorption, extensive
accumulation in untreated plant components, particularly leaves, and slow
metabolism all played an active role in susceptibility of pigweed and
lambsquarter to foliar applications of ethofumesate. Stage of growth
also determined species response to photosynthesis after foliar treatment
with ethofumesate. The implication, therefore, is that both applied and
basic oriented researchers must remain cognizant of potential differences
in response to treatment of plants in varied stages of morphological and
physiological growth.

In conclusion, it is apparent from these studies why variations
exist in selectivity of ethofumesate in sugarbeet. The preplant or pre-
emergence herbicide used, stage of growth of sugarbeet and weed species

at treatment, and environmental factors should all be considered when

85

selecting the specific foliar herbicide treatment. Obviously, the weed
population is also an important consideration. The time is past for the

"spray and pray" approach to weed control.

10.

11.

12.

13.

86

LITERATURE CITED

Arndt, R., R. Rusch, H. Benzner, and K. V. Gierke. 1970. Die
Beeinflussung der Selektivitat von phenmedipham durch verschiedene
faktoren. Z. Pfanzenkr. Sonderh. V:89-93.

Bethlenfalvay, G. and R. F. Norris. 1975. Phytotoxic action of
desmedipham: Influence of temperature and light intensity.
Weed Sci. 23:499-503.

Bischof, F., W. Koch, J. C. Majumdar, and F. Schwerdtle. 1970.
Retention, penetration and verlust von phenmedipham in
Abhangigkeit von einigen factoren. A. Pflanzenkr. V: Sonder.
pp. 95-102.

Crafts, A. S. and S. Yamaguchi. 1964. The Autoradiography of plant
material. Calif. Agr. Exp. Sta. Ext. Serv. Manual 35. 143 pp.

Davis, D. G. and K. F. Dusbabek. 1973. Effect of diallate on foliar
uptake and translocation of herbicides in pea. Weed Sci. 21:16-18.

Dawson, J. H. 1975. Cycloate and phenmedipham as complimentary
treatments in sugarbeet. Weed Sci. 23:478-485.

Dewey, O. R., P. Gregory, and R. K. Pfeiffer. 1956. Factors affect—
ing the susceptibility of peas to selective dinitro-herhicides.
Proc. 3rd Brit. Weed Control Conf. 1:313-326.

Duncan, D. N., W. F. Meggitt, and R. C. Bond. 1976. Weed control
evaluations at different stages of growth in sugarbeet. Research
Report N. Cent. Weed Contr. Conf. 33:170.

Duncan, D. N. and W. F. Meggitt. 1977. Sugarbeet weed control
evaluations for field and lab - 1976. Proc. 19th Reg. Meeting
Amer. Soc. Sugarbeet Technol. pp. 38-41.

Duncan, 0. N., W. F. Meggitt, and D. Penner. 1977. A mode of
action of ethofumesate. Weed Sci. Soc. Amer. Abstr. p. 84.

Duncan, D. N., W. F. Meggitt, and R. C. Bond. 1977. General weed
control evaluations in Michigan sugarbeets. Research Report N.
Cent. Weed Contr. Conf. 34:139.

Duncan, D. N., W. F. Meggitt, and D. Penner. 1978. Increased
activity from interactions of ethofumesate combinations in
sugarbeet. Weed Sci. Soc. Amer. Abstr. p. 94.

Duncan, D. N., W. F. Meggitt, and D. Penner. 1978. The basis for
selectivity of root-applied ethofumesate in sugarbeet and three
weed species. Weed Sci. (Submitted).

14.

15.

16.

17.

18.

19.

20.

22.

23.

24.

25.

26.

87

Ekins, W. L. and C. H. Cronin. 1972. NC 8438, a promising new broad
spectrum herbicide for sugarbeet. J. Amer. Soc. Sugarbeet Technol.
17:134-143.

Eshel, Y., E. E. Schweizer, and R. L. Zimdahl. 1976. Sugarbeet
tolerance of postemergence applications of desmedipham and
ethofumesate. Weed Res. 16:249-254.

Eshel, Y., R. L. Zimdahl, and E. E. Schweizer. 1976. Basis for in-
teractions of ethofumesate and desmedipham on sugarbeet and weeds.
Weed Sci. 24:619-626.

Flore, J. A. and M. J. Bukovac. 1974. Pesticide effects on the
plant cuticle: 1. Response of Brassica oleracea L. to EPTC as
indexed by epicuticular wax production. Proc. Amer. Soc. Hort.
Sci. 99(1):34-37.

 

Gentner, W. A. 1966. The influence of EPTC on external foliage
wax development. Weeds 14:27-31.

Hammerton, J. L. 1967. Environmental factors and susceptibility
to herbicides. Weeds 15:330-336.

Hendrick, L. W., W. F. Meggitt, and D. Penner. 1974. Basis for
selectivity of phenmedipham and desmedipham on wild mustard,
redroot pigweed, and sugarbeet. Weed Sci. 22:179-184.

Hoagland, D. R. and D. I. Arnon. 1950. The water culture method
for growing plants without soil. California Agr. Exp. Sta.
Circ. 347: 32 pp.

Holmes, H. M., R. K. Pfeiffer, and W. Griffiths. 1974. Pre-emergence
and post-emergence use of ethofumesate in sugarbeet. Proc. 12th
British Weed Cont. Conf. 493-501.

Juniper, B. E. 1957. The effect of pre-emergent treatment of peas
with trichloroacetic acid on the submicroscopic structure of the
leaf surface. New Phytol. 58:1-5.

Kolattukudy, P. E. 1965. Biosynthesis of wax in Brassica oleracea.
Biochemistry 4:1844-1855.

 

Laufersweiler, H. and C. M. Gates. 1972. Response of weeds and
sugarbeets to EP-475, a phenmedipham analog. J. Amer. Soc.
Sugarbeet Technol. 17:73-110.

Leavitt, J. R. C., D. N. Duncan, D. Penner, and W. F. Meggitt. 1978.
Inhibition of epicuticular wax deposition on cabbage by ethofume-
sate. Plant Physiol. (In Press).

27.

28.

29.
30.
31.

32.

33.

88

Norris, R. F. and R. A. Lardelli. 1976. Influence of time of day
at spraying on activity of phenmedipham and desmedipham. Res.
Prog. Rep., West. Soc. Weed Sci. pp. 143-146.

Pfeiffer, R. K., O. R. Dewey, and R. T. Brunskill. 1959. Further
investigation on the effect of pre-emergence treatment with
trichloroacetic and dichlorpropionic acids on the subsequent
reaction of plants to other herbicidal sprays. Proc. 4th Int.
Cong. Crop Protection 1:523—525.

Private communication with the F a M Beet Sugar Foundation Research
Group.

Putnam, Alan R. and Donald Penner. 1974. Pesticide interactions in
higher plants. Residue Reviews 50:73-110.

Schweizer, E. E. 1976. Persistence and movement of ethofumesate in
soil. Weed Res. 16:37-42.

Sharpe, N., O. Segarceanu, L. Ciorlaus, I. Popivici, I. Clotan, and
C. Nagy. 1974. The efficiency of herbicides based on pyrazon,
ethofumesate, lenacil, and phenmedipham, used alone or in combi-
nation, in sugarbeet grown under Romanian conditions. Proc. 12th
British Weed Cont. Conf. 477-483.

Winter, S. R. and A. F. Wiese. 1978. Phytotoxicity and yield re-
sponse of sugarbeet (Beta vulgaris) to a mixture of phenmedipham
and desmedipham. Weed Sci. 26:1-4.