SELECTMTY or PHEMMEDIPHAM _:
(METHYL___ M HYDROXYCARBANILATE  _1 j
M METFYLCARBAMLATE) AND ‘ ~- ‘-
ETHYL M HYDROXYCARBANILATE
CARBAMLATE we saw BEET

 

Thesis for the Degree of Ph D.
MICHIGAN STATE UNIVERSITY
LARRY WAYMAN HENDRICK

A 1973 A

 

LIBIwr ARY

Michigm State
University

 

This is to certify that the

thesis entitled

Selectivity of Phenmedipham (Methyl g—Hydroxycarbanilate
fi-Methylcarbanilate) and Ethyl E—Hydroxycarbanilate
Carbanilate in Sugar Beet

presented by

Larry Wayman Hendrick

has been accepted towards fulfillment
of the requirements for

Ph.D. Crop & Soil Sciences

degree in

 

 

Major professor

Date April 20, 1973

 

0-7 639

   
 
     

ramnmc av "
HOAG a SBNS' E

_ BOOK BINDERY INC.

LRY BINDERS

ABSTRACT
SELECTIVITY OF PHENMEDIPHAM (METHYL MfHYDROXYCARBANILATE
flfMETHYLCARBANILATE) AND ETHYL MfHYDROXYCARBANILATE
CARBANILATE IN SUGAR BEET
By

Larry Wayman Hendrick

Phenmedipham (methyl mrhydroxycarbanilate memethyl-
carbanilate) and EP-475 (ethyl mrhydroxycarbanilate
carbanilate) were applied to sugar beet (Beta vulgaris L.)
locations in different years. Broadleaf weed control was
obtained at rates of 1.12 to 1.68 kg/ha (l to 1.5 lb/A) or
slightly less when in combination with other herbicides.
No herbicidal treatment reduced root yield or the sugar
content, even when a high level of foliar inhibition was
observed. EP-N75 must be included as a postemergence

treatment to obtain effective redroot pigweed (Amaranthus

 

retroflexus L.) control. Studies in the laboratory were
conducted to observe the effect of phenmedipham and EP—u75

on photosynthesis of wild mustard [Brassica kaber (DC.)

 

L.C. Wheeler "pinnatifida" (Stokes) L.C. Wheeler], redroot
pigweed, and sugar beet. Sugar beet recovered from the
initial inhibition of photosynthesis due to herbicide
application but wild mustard did not. Photosynthesis in
redroot pigweed was permanently inhibited by EP-h75 but

was temporarily inhibited by phenmedipham. Further labora—
tory studies were conducted to determine the basis for

selectivity of these two herbicides in these three species

 

 

 

v‘ I
’I

Larry Wayman Hendrick

by evaluating spray retention, absorption, translocation,
and metabolism. Selectivity can not be explained by
differences in Spray retention or absorption. Only acro—
petal translocation of this herbicide was observed. Redroot
pigweed translocated more EP-u75 than phenmedipham. Sugar
beet metabolized both herbicides quickly but wild mustard
did not. Redroot pigweed metabolized phenmedipham quickly
but metabolized EP-H75 slowly. This difference in metabo-
lism was the difference in the rate of the initial detoxi-

cation reaction involving the parent herbicide.

SELECTIVITY OF PHENMEDIPHAM (METHYL flfHYDROXYCARBANILATE
flfMETHYLCARBANILATE) AND ETHYL MfHYDROXYCARBANILATE
CARBANILATE IN SUGAR BEET

By

Larry Wayman Hendrick

A THESIS

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

DOCTOR OF PHILOSOPHY

Department of Crop and Soil Sciences

1973

kdfivv ACKNOWLEDGEMENTS

The author wishes to gratefully acknowledge the
assistance of Dr. William F. Meggitt in conducting this
study and in making the rewarding experience at M.S.U.
possible. To Dr. Donald Penner is extended a special
acknowledgement for his laboratory guidance. The author
wishes to thank Dr. Neil Jenny of Nor-Am Agricultural
Chemicals for his technical assistance. Also the
assistance of Drs. J. M. TiedJe, C. J. Pollard, and

G. J. Hogaboam is gratefully acknowledged.

ii

TABLE OF CONTENTS

ACKNOWLEDGEMENTS . . . . . . . . . . . . .

LIST OF TABLES . . . . . . . . .

LIST OF FIGURES . . . . . . . . . . . . . . . .

INTRODUCTION . . . . . . . . . . . .

CHAPTER 1: CARBANILATES AND RELATED HERBICIDES
Weeds and Crops . .

Efficacy of Phenmedipham and EP— A75 in Sugar
Beets . . . . . . . . . . . . . . .

Phenmedipham and Soils
Effect of Phenmedipham on Photosynthesis . .
Factors for Selectivity of Herbicides

A. Retention of Herbicides on Leaves

B. Absorption and Translocation of
Herbicides . . . .

C. Metabolism of Carbamates
D. Metabolism of Phenmedipham and EP—A75

CHAPTER 2. SELECTIVE USE OF PHENMEDIPHAM AND EP-
A75 ON WILD MUSTARD, REDROOT PIGWEED, AND SUGAR

BEET . . . . . . . . . . . . . . . .
Abstract . . . . . . . . . . . . . . . . .
Introduction . . . . . . . .

Materials and Methods . . . . . . .
Results and Discussion . . .
Literature Cited . . . . . . .

iii

Page
ii

vii

\O\DO\U'IUU

l6
l6
l6
18
20
30

Table of Contents (Cont.) Page

CHAPTER 3: BASIS FOR SELECTIVITY OF PHENMEDIPHAM
AND EP-N7S ON WILD MUSTARD, REDROOT PIGWEED, AND

SUGAR BEET . . . . . . . . . . . . . . . . . . . 31
Abstract . . . . . . . . . . . . . . . . . . 31
Introduction . . . . . . . . . . . . . . . . 32
Materials and Methods . . . . . . . . . . . . 35
Results and Discussion . . . . . . . . . . . A3
Literature Cited . . . . . . . . . . . . . . 66

CHAPTER A: SUMMARY AND CONCLUSIONS . . . . . . . 67
LIST OF REFERENCES . . . . . . . . . . . . . . . . 70
APPENDICES . . . . . . . . . . . . . . . . . . . . 7“

iv

LIST OF TABLES

Table Page
CHAPTER 2

1. Visual weed control ratings of postemergence
and preemergence plus postemergence herbicidal
combinations in sugar beets in Lenawee County,
Michigan, 1971 . . . . . . . . . . . . . . . . 21

2. Visual weed control ratings of postemergence
and preemergence plus postemergence herbicidal
combinations in sugar beets in Lenawee County,
Michigan, 1972.. . . . . . . . . . . . . . . . 22

3. Visual weed control ratings of postemergence
and preemergence plus postemergence herbicidal
combinations in sugar beets in Saginaw County,
Michigan, 1971 . . . . . . . . . . . . . . . . 23

A. Visual weed control ratings of postemergence
and preemergence plus postemergence herbicidal
combinations in sugar beets in Saginaw County,
Michigan, 1972 . . . . . . . . . . . . . . . . 2A

5. Visual weed control ratings of double postemer-
gence and preemergence plus double postemergence
combinations in sugar beets in Bay County,

Michigan, 1972 . . . . . . . . . . . . . . . . 25

6. Yields of sugar beets in Lenawee County, Michi-
gan, 1971 . . . . . . . . . . . . . . . . . 28

7, Kilograms recoverable white sugar per 1000 kg
of sugar beet roots in Bay County, Michigan, 1972 29

CHAPTER 3

1. Mean percent of initial total photosynthesis of
three species due to herbicide treatment . . . AA

2. Mean percent of initial dark respiration of three
species due to herbicide treatment . . . . . . A5

List of Tables (Cont.)

Table Page

3. Amount of 1uC-herbicide retained on leaves of
three species . . . . . . . . . . . . . . . . A9

A. Absorption of l[AC-herbicides .

. . . . . . 50
5. Percent of 14C from absorbed herbicide trans-

located acropetally in the same leaves of three
species . . . . . . . . . . . . . . . . . . . 60

6. Percent of translocated luC-herbicides meta-

bolized after 5 and 2A hr . . . . . . . . . 62

vi

LIST OF FIGURES

Figure

CHAPTER 3

1. Molecular structure of EP- A75 (top) and phen-
medipham (bOttom) o o o o o o o o o o o

2. Sealed plastic chamber used for photosynthesis
and respiration studies . . . . . . . . . .

3. Photomicrographs of lower leaf surfaces of
treated and untreated plants . . . . . . . . .

A. Translocation of l[AC-phenmedipham (C) and lAC_
EP-A75 1 day after foliar application . . . .

5. Translocation of l[AC-phenmedipham (A) and 1AC_
EP-A75 6 days after foliar application . . . .

6. Distribution of root applied luC-phenmedipham

7. Distribution of root applied lL‘C-EP-A75 .

8. Chromatographic separation of lLAC-phenmedipham
metabolites using solvent system II . . . .

9. Chromatographic separation of luC-EP-A75 meta-

bolites using solvent system II . . . . . . .

vii

Page

33

36

A7

51

53
56
58

63

6A

INTRODUCTION

It has been shown that weeds have the potential to
harm crop plants and thus cause economic loss (5, 31, Al,
A3). In Michigan sugar beets, redroot pigweed is a major
annual broadleaf weed problem.

A new postemergence herbicide, EP—A75 (ethyl T?
hydroxycarbanilate carbanilate) has been reported to kill

redroot pigweedl

(l, 9, 26). Phenmedipham (methyl m:
hydroxycarbanilate memethylcarbanilate) is an analog of
EP-A75 that exhibits little or no activity on redroot
pigweed. The purpose of this research was to study the
use and selectivity of EP-A75 and phenmedipham in sugar

beets.

 

1Dawson, J. H. 1971. Effects of herbicides on sugar
beets. Weed Sci. Soc. Amer. Abstr. No. 3.

CHAPTER 1
Carbanilate and Related Herbicides
Weeds and Crops

Under a noncompetitive situation, one redroot pigweed
plant can produce 229,000 seeds and wild mustard can pro-
duce 1,200 to 2,700 seeds per plant (35, 22). But when
there were 60 redroot pigweed plants per 0.8A sq m, 5,200
viable seeds were produced per plant (35).

Brimhall, g§_al. (5) found that redroot pigweed den—
sities of one per eight sugar beets or greater reduced
the root weight of beet roots and beet tops but did not
affect percentage sugar. This reduction in yield was
attributed to competition for light. On a plant basis,
broadleaf weeds reduced sugar beet root yield more than
grass weeds (5, A3). .

Weatherspoon and Schweizer (A1) found a significant
reduction in root yield and total pounds of sucrose per

acre with only one kochia (Kochia scoparia (L) Schrader)

 

plant per 7.5 meters of sugar beet row. Percent sucrose
was significantly reduced only when there was one kochia

plant or more per 30.5 cm of row.

1

Miller found that any density of weeds used reduced

 

1Miller, J. R. 1963. An evaluation of competition
between weeds and sugar beets (Beta vulgaris L.). Ph.D.
Thesis. Michigan State University, East Lansing. 85p.

 

sugar beet yield if the weeds remained in the beets longer
than A weeks. The percent sucrose of the harvested root
was not affected by weed competition.

Shadbolt and Holm (31) showed a loss in yield in
vegetable row crops due to present of redroot pigweed and
water hemp (Acnida sp.).

Efficacy of Phenmedipham and EP-A75
in Sugar Beets

 

Arndt and Kotter (1) showed that postemergence appli-
cation of phenmedipham was more selective in cotyledonary
sugar beets and weeds at 0.25 kg/ha, and in older sugar

beets at 0.50 kg/ha or more, on common chickweed (Stellaria

 

media (L.) Cyrill), (Senecio vulgaris L.), common lambs-

 

quarters (Chenopodium album L.), henbit (Lamium amplexicaule

L.), white mustard (Sinapis alba, Grey), and galinsoga

 

(Galinsoga parviflora, Gav), knapweed (Centaurea cyanus

 

L.), bedstraw (Galium aparine L.), and (Algpecurus

 

myosuroides Huds). Redroot pigweed at these growth stages
showed little susceptibility at these rates but showed
susceptibility at rates injurious to the sugar beet.
Dexter (9), studying various herbicides used for weed
control in sugar beet, found that no individual herbicide
gave good broad spectrum weed control unless postemergence
applications of phenmedipham or pyrazon (5-amino-A-chloro-
2-phenyl-3 (2H)-pyridazinone) plus dalapon (2,2-dichloro-

propionic acid) followed a preemergence or preplant

incorporated treatment. Initial sugar beet injury increased
with the use of combinations but no yield reductions
resulted.

Dawson2 found that sugar beets were tolerant of phen—
medipham but were injured under certain unfavorable weather
conditions. However, injury was temporary and the sugar
beets recovered.

Schweizer and Weatherspoon (30) found that phenmedi-
pham did not satisfactorily control pigweed seedlings that
had two to five leaves but was controlled by EP-A75.

EP—A75 may injure sugar beets more than phenmedipham but
sugar beet tolerance and weed control may be improved by
a mixture of phenmedipham plus EP-A75.

Edwards (11) applied Schering formulation No. A075
containing 16.7 percent (w/w) phenmedipham at 1.12 kg/ha on
red beets and obtained good control of most annual broad—
leaved weeds in very young stages. A spray volume of
187 L/ha gave better weed control than other volumes used.

Holmes (17) also applied Schering formulation No.

A075 at 1.12 kg/ha and found that it gave postemergence
control of most important annual broadleaved weeds except
prostrate knotweed (Polygonum aviculare L.) in sugar beets
and did not affect crop stand, yield of roots, or sugar

content.

 

2Dawson, J. H. 1971. Effects of herbicides on sugar

beets. Weed Sci. Soc. Amer. Abstr. No. 3.

Miller and NalewaJa (26) applied phenmedipham with
various additives in the field and greenhouse and found
that nonphytotoxic oils were more effective than surfac-
tants as additives to phenmedipham on green foxtail
(Setaria virdis (L) Beauv.), yellow foxtail (Setaria
glauca (L.) Beauv.), redroot pigweed, or common lambs-
quarters. No additive used enhanced herbicidal activity
on kochia or wild mustard. Linseed oil reduced the
herbicidal activity of phenmedipham on kochia.

Van der Zweep3

, et_a1, measured l“002 assimilation
in sugar beet as affected by single drop applications of
phenmedipham solutions. They detected a local inhibition
of photosynthesis and no systemic effect and concluded

that uniform foliar coverage was necessary to kill

susceptible plants.
Phenmedipham and Soils

Kossmanu considered uptake from soil of phenmedipham
to be insignificant due to the chemical's inherent pro-
perties of strong adsorption in upper layer of soil, its

slight water solubility (3 ppm), and its high sensitivity

 

3Van der Zweep, W., J. L. P. Van Oorschot, and A.
Reisler. 1969. Laboratory studies on the selectivity of
phenmedipham. Scientific and practical experience in using
phenmedipham for weed control in beets, Berlin, January
1969. Abstr. (of conf. sponsored by) Schering AG. 1969.

p. 10-11.

“Kossman, K. 1969. Phenmedipham residues in plant
and soil. Scientific and practical experience in using
phenmedipham for weed control in beets, Berlin, January
1969é Abstr. (of conf. sponsored by) Schering AG. 1969.
p. l -20.

to hydrolyzing agents. He also found that phenmedipham
is continuously decomposed in the slightly acid soils of
low organic matter content used for beet production (23).
Half-lives of 28 to 55 days were recorded, depending on
experimental conditions and soil type. In the field

the formulated herbicide penetrated only very little
beyond a depth of 12.7 cm.

Sonawane and Knowles (33) examined decomposition of
phenmedipham and meaminophenol in alkaline soil and found
that phenmedipham is hydrolyzed to mgaminophenol via
methyl mrhydroxycarbanilate. In the soil the memethyl-
phenol can undergo physical adsorption and chemical

complexing with soil components.
Effect of Phenmedipham on Photosynthesis

El-Sharkawy and Hesketh (12) measured the rate of CO2
fixation in several species and found that pigweed had
twice the fixation rate of sugar beet and a fixation rate
equal to that of corn (Egg mays L. "Funks G711A"), bermu-
dagrass (Cynodon lactylon (L.) Pers. "Coastal") and grain
sorghum (Sorghum vulgare L. "Hegari"). The redroot pig-
weed had similar leaf anatomical characteristics to the
above tropical grasses.

Chen, g£_§l. (7) presented data that supports the
hypothesis that many high photosynthetic capacity plants,

which also includes many crOp plants,are very competitive

plants and often become serious weeds. Usually plants

such as redroot pigweed with high photosynthetic CO2
fixation rates have a low CO2 compensation concentration.

Good (1A) noted that the atomic configuration common
to all Hill reaction inhibitors may be represented by

R'-N-fi-R", where X represents a nitrogen or oxygen atom.

H X
The nitrogen must be attached to a group of considerable
size, but it must not sterically alter the activity of
the nitrogen.

Van Overbeek (39) noted that although srtriazines,
phenylureas, and acylanilides have similar biological
actions, they are dissimilar in structure. Their biologi-
cal activity must not be due to covalent bond reactions.
As also noted by Good above, the similarity these classes
of herbicides have must be responsible for their biologi-
cal activity, obtained by hydrogen bonding of the common
NH group and C=0 or C=N groups to protein of an enyzme
involved in oxidation of water.

Shaw (32) found a high degree of correlation between
molecular configuration and herbicidal activity of various
carbamates.

Kotter and Arndt (2A) found that phenmedipham causes

a rapid decrease of CO assimilation in both resistant

2
and susceptible plants, but a resistant plant such as
sugar beet soon recovers. Dark respiration of sugar beet
was inhibited later in time than was CO2 assimilation.
Dark respiration of sugar beet was inhibited less than

that of mustard. The latter was permanently affected
but sugar beet recovered.

Arndt and Kotter (1) used starch content as an indi-
cator of the photosynthesis rate of wild mustard and sugar
beet as influenced by treatment of phenmedipham. He
found that the starch content of wild mustard dropped
greatly 2A hours after treatment. In isolated chloroplasts
they found no difference in the inhibition of the Hill
reaction of a sensitive plant compared to a resistant
specie. By using an infrared CO2 gas analyzer to measure
photosynthesis in intact plants, they found that phenmedi-
pham suppressed CO2 assimilation in sugar beet and weeds
but sugar beet and redroot pigweed completely recovered
and the other weeds did not. The rapid recovery of sugar
beet and redroot pigweed after treatment was attributed
to the possibility of rapid metabolism or difference in
absorption.

Willenbrink5 found a 90 percent inhibition of the
photosynthetic rate in intact wild mustard (Sinapis
arvensis L.) with phenmedipham. Further metabolic experi-
ments indicated that during photosynthesis it is the Hill

reaction which is inhibited by phenmedipham.

 

5Willenbrink, J. 1969. The action of phenmedipham
on the CO fixation during photosynthesis in young sugar
beet leav 8. Scientific and practical experience in
using phenmedipham for weed control in beets, Berlin,
January 1969. Abstr. (of conf. sponsored by) Schering
AG. 1969. p. 7-9.

Factors for Selectivity_pf Herbicides

 

Buchel (6) stated that all the work with chloroplasts
on mechanism and maximum activity had no relation to the
selectivity of herbicides. He went on to say that a
selective herbicide is the result of an empirical long
range field testing and is more a statistical event than
a result of scientific design. He believed that the work
with chloroplasts does not help significantly and that
more fundamental plant physiology and experiments with
intact species are necessary.

Robertson and Kirkwood (28) stated that if the
effectiveneSs of a herbicide is dependent on the concen—
tration of the chemical reaching the site of action, then
any factor that affects the rate of accumulation at that
site must be considered in the overall view of the mode

of action of the herbicide.

A. Retention of Herbicides on Leaves

 

Hibbitt (16) used wild oat (Avena fatua L.) and flax

 

(Linum usitatissimum L.) to study retention of sprays on

 

leaf surfaces. With growth of wild oat, an increase in
amount of spray retained per plant and per unit weight of
plant occurred. A constant volume of spray per plant was
retained on flax as it grew, related to a decrease in
projected surface area which is exposed to spray as a

proportion of the whole. Also, cotyledons retain greater

lO

amounts of spray per unit weight than true leaves.

B. Absorption and Translocation of Herbicides

Robertson and Kirkwood (29) reviewed several factors
influencing absorption of herbicides. Mature leaves
absorb less than expanding leaves due to the thick cuti—
cles. Rapid penetration is possible through the thin
cuticle at veins and the midrib. Higher moisture conditions
will swell the hydrophilic groups of the cuticle, pushing
the apolar wax units apart promoting apoplastic absorption
of water-soluble herbicides. The heavy esters of 2,A-D
(2,A-dichlorOphenoxyacetic acid) are absorbed greater than
other formulations of 2,A-D but must be converted to the
acid moiety before translocation.

Initial studies6 indicated that very little leaf-
applied phenmedipham could be found in the roots of sugar
beet or in the top and root residue even 28 days after
application. Phenmedipham content in sugar beet tops
reached a maximum at 1A days after application.

Bischof, e£_al. (3) found that high light intensity
increased the phenmedipham content in sugar beet and
white mustard (Sinapis alba, Grey). Sugar beet was damaged
at temperatures of 30 and A0 C but the decline of phen-

medipham content in both beets and mustard was quicker at

 

6Jenny, N. Personal communication. Nor-Am Agricul-
tural Chemicals, Woodstock, Illinois.

11

higher temperatures than at lower temperatures. Both
sugar beet and mustard absorb phenmedipham from nutrient
solutions and from foliar application in similar amounts.
One hour after leaf application, the largest portion of
the absorbed compound had already penetrated, which was
only a small portion of that applied. Greatest pene-
tration occurred when the sugar beet and mustard had full

cotyledonary leaves and one-half formed first true leaves.

C. Metabolism of Carbamates

Kearney (20) isolated and characterized an enzyme
obtained from Pseudomonas sp. that will hydrolyze car-
banilate compounds to aniline and alcohol analogs. It
also exhibits amidase activity as it will hydrolyze some
acylanilides but not phenylureas.

James and Prendeville (18) used smartweed (Polygonum
lapathifolium L.), redroot pigweed, and tomato (Lycoper-

sicum esculentum Mill.) to study metabolism of chlor—

 

propham (isopropyl mechlorocarbanilate). They found a
similar conversion to B-glucosides in all species. There
was no modification of the aromatic ring, hydrolysis of
the ester linkage, or conversion to an N—hydroxy deriva—
tive. They projected that the isopropyl portion must be

oxidized at the -CH3 group to -CH OH, thus glycoside for-

2
mation could occur readily.
Still (36) examined metabolism of root applied

propanil (3',A'-dichloropropionanilide) in rice (Oryza

l2

sativa L.) plants and found that the parent compound is
degraded to 3,A-dichloroaniline and propionic acid. The
3,A-dichloroaniline was first complexed as N-(3,A-dich-
lorophenyl)—glucosylamine, and then to other unidentified
complexes.

Yih (A2) used foliar applied prOpanil on rice plants
to investigate metabolism of the herbicide, finding similar
results as Still (37). But he found that the aniline-
carbohydrate complexes were minor and that the major por-
tion of the 3,A-dichloroaniline is complexed to lignin.
The parent compound did not complex to lignin.

Mann, gt_al. (25) found that carbanilates inhibited
amino acid utilization by susceptible species, occurring
very soon after contact of the herbicide with plant
tissue. He noted that carbamate herbicides and proteins
have a common structure, the peptide bond.

Chin, et_al. (8) studied metabolism of swep (methyl
3,A-dichlorocarbanilate) in A—week old rice plants,
finding a stable swep-lignin metabolite in the straw,
hulls, and bran, but no residue in the endosperm.

Still and Mansager (37) studied metabolism of root-

applied chlorpropham in soybean (Glycine max (L.) Merr.)

 

plants and found there was acropetal translocation in
these plants and that the carbanilate bond was not broken
in metabolism. The polar metabolites of chlorpropham
were not translocated once formed in the root or shoot.

They suggested that the chlorpropham phenyl nucleus was

l3

hydroxylated or oxidized.

Studies conducted by Dittert and Higuchi (10) on
hydrolysis of carbamates in alkaline solutions strongly
suggested that initial cleavage would be expected to occur
at the ester bond. The rate of hydrolysis would depend
upon the degree of substitution of the nitrogen.

Bordeleau and Bartha (A) found that azobenzene
residues can be formed from variously substituted aniline
degradation products of aniline based herbicides in soil.

Bartha and Pramer (2) established that prOpanil
decomposes in soil to carbon dioxide and 3,A-dichloro-
aniline, and the latter forms 3,3',A,A'-tetrachloroazo-

benzene. All reactions involved soil microorganisms.

D. Metabolism of Phenmedipham and EP-A75

Sonawane and Knowles (3A) administered EP-A75 and
phenmedipham orally to white rats and studied the meta-
bolism of these two compounds excreted in urine. They
found that both chemicals were rapidly metabolized to
ethyl mehydroxycarbanilate and methyl mehydroxycarbanilate,
respectively. Both metabolites subsequently went to
meaminophenol, and then were N-acetylated to form 3'hydroxy-
acetanilide. All of these metabolites were found com-
plexed to natural plant components such as glucuronic
acid.

Kotter (10) found that phenmedipham at 3.3 x 10-5 M

had no influence on the enzymes catalase, peroxidase,

1A

and transaminase in vitro, and slight inhibition on
glutamate dehydrogenase. There was no effect on citric
acid cycle enzymes. There was a strong affinity between
phenmedipham and chloroplast membranes, and some adsorp-
tion by the chloroplasts was found.

Kassebeer (11) found that a larger amount of phen-
medipham entered the foliage of sugar beet and various
weeds within the first A hours after application. Eight
hours after treatment, translocation of phenmedipham within
the plant was observed, moving mainly in the direction of
the transpiration stream. A very rapid distribution of
the compound was observed in wild mustard. Also 8 hours
after treatment the beets had decomposed 20 to A0 percent
of the compound while the weeds used decomposed only
traces of it. All the plants used, except sugar beet,
decomposed most of the phenmedipham into methyl mghydroxy—
carbanilate and into memethylaniline, which in turn can
combine with water soluble compounds in plants. Sugar
beets decomposed phenmedipham in a different manner than
the weeds. In another study, Kassebeer (l9) pointed out
that even though leaves of some plants are killed, the
plant may survive due to a protected growing point and
lack of basipetal translocation of phenmedipham. He
found that sugar beet rapidly absorbed phenmedipham but
metabolized it rapidly, as did redroot pigweed, but
with slightly slower metabolism. Some susceptible species

had comparably slower metabolism and also slower absorption

15

of phenmedipham. It was concluded that there was no
single path of metabolism to account for selectivity but
rather the plant species inactivated phenmedipham in
different ways. Neither uptake nor rate of degradation
alone explained the selectivity of phenmedipham on species
tested. There was a straight relationship between suscep-
tibility of various species and their content of parent
material since resistant species have a lower and suscep—
tible species have a higher content of active ingredient,
which is a function of both absorption and metabolism.

Knowles and Sonawane (21) investigated the fate of
foliar applied EP-A75 in sugar beet over a 90-day period,
and found that the amount of parent compound decreased and
decomposition products increased during this time. The
major metabolite was ethyl mghydroxycarbanilate. Also,
smaller amounts of mfaminophenol and very polar compounds
were evident.

Looking at possible breakdown products of phenmedi-
pham, and of EP-A75 due to structural similarities, three
different reactions could be expected as the first degra-
dation steps, as typical of methyl- and phenylcarbamates
(15). These are:

(1) direct combination with plant constituents,

(2) hydroxylation of the compounds,

(3) cleavage of the ester linkages of the compounds.

CHAPTER 2

Selective Use of Phenmedipham and EP-A75 in Michigan
for Weed Control in Sugar Beets

Abstract

Research was conducted to examine the possible use of
phenmedipham (methyl mehydroxycarbanilate memethylcarbani-
late) and EP-A75 (ethyl mfhydroxycarbanilate carbanilate)

for weed control in sugar beets (Beta vulgaris L.).

 

Various treatments of phenmedipham, EP-A75 and pyrazon
(5-amino-A—chloro-Z-phenyl-3(2H)-pyridazinone) were applied
to sugar beets postemergence with and without a preemergence
treatment of pyrazon + TCA (trichloroacetic acid) at various
locations in different years. Weed control was greater
with preemergence plus postemergence combination than with
pre- or postemergence alone. Crop injury resulting from
combination treatments did not affect yields. Double post-
emergence applications did not adversely affect the crop

or recoverable sugar content compared to single post-
emergence treatments. EP-A75 was necessary for redroot

pigweed (Amaranthus retroflexus L.) control.

Introduction

Effective herbicidal weed control in Michigan sugar
beets frequently involves the combined use of preemergence

and postemergence applications. The trend toward minimum

16

l7

labor used in sugar beet fields necessitates total weed
control.

The preemergence herbicide treatment often used on
heavier soils in Michigan is a pyrazon plus TCA at A.5
kg + 6.7 kg/ha (A lb + 6 lb/A). In a favorable environ-
ment, good control of many broadleaf and grass weeds is
obtained. However, frequently an application of a post-
emergence herbicide such as phenmedipham is needed to
control many of the escaped broadleaf weeds or some
grasses (l, 2, 3, A). Redroot pigweed is an annual broad-
leaf weed that phenmedipham will not control. EP-A75, an
analog of phenmedipham, is effective on pigweed (8).

Phenmedipham and EP-A75 have phytotoxic activity only
when applied as a foliage treatment. Upon contact with
soil, the chemicals are no longer active1 (5, 9).

Phenmedipham and EP-A75 may cause foliar injury to
sugar beets under adverse environmental conditions or when
used in combinations with preemergence herbicides. However,
crop stand, final yield, and sugar content are usually
not affected2 (2, A, 8). Addition of nonphytotoxic oils
or concentrates will increase herbicidal activity of these

compounds on many weed species (6, 8).

 

1Kossman, K. 1969. Phenmedipham residues in plant
and soil. Scientific and practical experience in using
phenmedipham for weed control in beets, Berlin, January
1969é Abstr. (of conf. sponsored by) Scherling AG. 1969.
p. l -20.

2Dawson, J. H. 1971. Effects of herbicides on sugar
beets. Weed Sci. Soc. Amer. Abstr. No. 3.

18

The objective of this research was to examine the
possible use of phenmedipham and EP-A75 for weed control
in sugar beets, by evaluating the efficacy, effect on
yield, and effect on recoverable sugar content of the

sugar beet root by these compounds.

Materials and Methods

 

To evaluate the efficacy of these two compounds,
research plots were maintained on farmers' sugar beet
fields at different locations in Michigan. Plot size was
3 or A 70-cm (28 in) wide rows by 13.5 m (A5 feet) long
arranged in a randomized complete block design with three
replications. All applications were broadcast by a
tractor-mounted sprayer in 215 L/ha (23 gpa) of water (7).

In 1971, preemergence and postemergence treatments
alone and in combination were applied to sugar beets on
a sandy loam soil with A percent organic matter in Lenawee
County, Michigan. Preemergence treatments were applied
on April 12 and postemergence treatments were applied on
May 11, when the sugar beet was in the 2-1eaf stage. Rain—
fall within 1 week after preemergence treatment was 1.3
cm (0.5 in) and the total rainfall received for a 3-week
period after application was 1.7 cm (0.7 in), the latter
being 70 percent below the seasonal mean.

At a second location in 1971, similar applications
were made on a clay loam soil with 12 percent organic

matter in Saginaw County, Michigan. Preemergence

19

applications were made on April 23 and postemergence
applications were made on June 2, when sugar beets had
full leaves. Rainfall within 1 week after preemergence
application was 0.2 cm (0.1 in) and within A weeks was
l.A cm (0.6 in), the latter being 56 percent below the
seasonal mean.

In 1972, the soil used in Lenawee County was a sandy
loam with 2 percent organic matter. Preemergence treat—
ments were applied on April 28 and the postemergence
treatments applied on May 17, when the first part of
sugar beet leaves were one-half expanded. Rainfall
within 1 week after preemergence application was 3.5 cm
(l.A in), and within A weeks after application was 7.3
cm (2.9 in), which approximates the seasonal mean.

In 1972, a second location was used in Bay County,
Michigan with a sandy clay loam soil with 33 percent
organic matter. Preemergence treatments were applied on
May 9 and postemergence treatments applied on June 5,
when the sugar beet was in the two-leaf stage, and again
on June 1A on selected plots. Rainfall within 7 days
after preemergence application was 0.5 cm (0.2 in) and
within A weeks was 2.1 cm (0.8 in), the latter being 52
percent below seasonal mean.

Visual ratings of herbicidal effectiveness were
usually obtained 1 to 2 weeks after postemergence appli-
cation. Ratings on crop injury represent initial crop

injury. Yields were taken in 1971 at Lenawee County by

20

harvesting the center two rows of the A-row plots. In
1972, juice from samples of sugar beet roots were taken
from plots in Bay County and analyzed for percent recover-
able sugar at Michigan Sugar Company, Saginaw, Michigan.

Yields and sugar contents were analyzed for significant

differences.
Results and Discussion

The weed control due to postemergence and preemer-
gence plus postemergence herbicide combinations are shown
in Tables 1, 2, 3, A, and 5. Crop injury due to postemer-
gence applications only was low except for the combina-
tions shown in Table 1. Especially notable was the lack
of sugar beet injury due to two postemergence applications
(Tables A, 5). Stand counts were made in 1972 but no
significant differences due to treatments were observed.3

In general, weed control was greater with a combina-
tion of treatments. When more than 10 cm (0.A in) of
rain fell the first week after preemergence application,
the best weed control was obtained (Tables 1 and 2). Due
to drier soil conditions at two locations, the preemergence
application resulted in poor weed control (Tables 3 and A).
However, when the postemergence treatments were applied,

a substantial increase in weed control was obtained over

 

19 3Meggitt, W. F. and L. W. Hendrick, unpublished data,
72.

 

A.q Sande Esfioomocozov onBAMSUmQqun

.mn\wx w~.m + :m.m pm <09 + consume mo Umpmfimcoo soameHaaam oUHOHnAoQ oocownoEoonQ one
.Hafix no Honpcoo mpoHQEoouOH .Hompcoo o: no manncfi ocuo

21

 

 

 

 

 

m
A.5 5.0 5.0 0.0 0.0 0.0 . soapsoaaoas
oocmwnosoumoa oz
0.0H o.oa o.m o.m o.oH >.H wo.a mmzlmm
o.oa 0.0H o.m o.m n.m 0.0 NH.H mmzlmm
0.00 o.oa 0.: m.m 0.0H m.o mm.a momzm
o.oa o.oa 0.: m.m m.m o.o NH.H momzm
0.0a 0.0a m.a 0.0 m.0 5.0 00.H saneflooesona
0.0H o.oa o.m w.m o.m o.o mH.H Emnaficoecocm
o.oa o.oa 0.m m.» o.m o.o ma.a+zm.m assuacoa
Icons + coumpzm
Asn\wx0
whoppmSU ooozwfig manna“ mpmpmmSU ooozwaa manna“ oumm pcmspmona
Imnqu poonvom mono n amnemq pooncom mono
coapwcHnEoo
mocowaosoumoa + oocowpoEoonm maco oocowposopmom
.Hema .cawanofiz .seesoo
oozmcoq CH muoon human CH mQOHpMCHnEoo mmnfioannon oocmwhoaopmon
mafia monoMAoEomna new mocowhoEoumoa mo mwcaumu HOMucoo coo: Hm3m0> .H manme

22

.0:\&& mm.0 + 0m.m pm 009 + coumpma mo 000000000 coapmofifiaam 000000L0£ 00:0wm0800pa 0:9

 

 

.A.q mfiaomfifimHE0pa0 000000600 0003m0m 000 .A.q 000090Ho momasppomv 0cmfimnsm
0800 £003 A.q Eznam 520000020300 090pnmsvwnsma 0000000800000 no 000000000 m0>00a000pm

 

 

.Hafix no Hoppcoo 000H0800u0H .Hoppsoo 0: Lo mashed ocuom

0.0 0.0 0.0 0.0 0.0 0.0 . eofieaosaoos
00:0wp0a0umoa 02
0.0a 0.00 m.H I I 0.0 mm.a mmzumm
0.0a 0.00 0.H m.0 0.H 0.0 q m.m+:m.0 H00 + mmzumm
0.0a 0.0a N.H m.H ~.H 0.0 A m.m+mH.H HHO + momzm
0.0a 0.0 0.0 0.0 ~.H 0.0 mm.a momzm
0.0a 0.0a m.H 0.: 0.H 0.0 NH.H momzm
0.0a m.m 0.0 0.H 0.0 0.0 00.H EmnafivmeC0£m
0.0a m.m 0.H 0.m m.H m.0 A m.m+mH.H H00
+ 50QQHO0EC0£m

0.0a 0.0a 0.H 0.0 m.H m.0 q m.m H00 +
+0m.0+am.m masumm + sonohsm

0.0H 0.0a 0.m 0.: m.m m.0 0 0.m Hfio + escafieos

 

 

 

 

+zm.0+:m.m IQ0£Q + commemm
necxmx0
m0>00a 0003wfiq means“ nm0>00a 0003wH0 madnCH 000m 0208000AB
Icmonm poon00m 0090 Icmonm poomu0m mono
soapmcfinEoo
00:0wp0s0pmoa + 0000wn0600nm maco 00:0mp080umom
0.mnma .cmwanoaz
.zucsoo 0030004 :0 00000 newSm ca mcofip00Hnsoo 000000090: 00:0wm0E0
upmoa mSHQ 0oc0wh050000 0:0 00:0MA0800000 ho madame Hoppcoo 0003 stmfi> .m 0anmb.

23

.00\00

00.0 + 00.: 00 000 + 0000000 00 000000000 00000000000 000000000 000000000000 00B

0003 .0.0 00000 0000o0m00000 0000000000000 0000000000000 00 000000000 00>00000o0m

 

 

.A.0 0000>0o>000 0000000000 000030000 0003 0000

0

.0000 00 0000000 00000000u00 .0000000 00 00 000000 00u00

 

 

 

 

 

0.0 0.0 0.0 0.0 0.0 0.0 u so00sofi0aas
0000000000000 02
0.0 0.0 0. 0.0 0.0 0.0 00.0 mpzumm
0.0 m.0 m. 0.0 0.0 0.0 00.0 000-00
0.0 0.00 m. 0.0 0.0 0.0 00.0 00020
0.0 0.0 0. 0.0 0.0 0.0 00.0 00020
0.00 0.0 0. 0.0 0.0 0.0 00.0 000000000000
0.00 0.0 0. 0.0 0.0 0.0 00.0 000000000000
m.0 0.0 0. 0.0 0.m 0.0 00.0+0m.m 000000000000
+ 0000000
020000
00>000 0003000 000000 000>000 0003000 000000 0000 000000000
100000 0000000 0000 I00o0m 0000000 0000
00000000000
0000000000000 + 000000000000 0000 0000000000000
0.0000 .00000000
.000000 3000000 00 00000 00000 00 000000000000 0000000000 000000000
10000 0000 000000000000 000 0000000000000 00 0000000 0000000 0003 00000> .0 00009

2h

.00\0x m0.0 + 00.: 00 009 + 0000000 00 000000000 00000000000 000000000 000000000000 009

.0.0 000000>000000 0000000000 000300000 0000>
10000000 000 0.0 00000000000000 0000000<v 0003000 000000 .A.0 0000>00>000 0000000000
000030000 0003 0000 000 0.0 00000 000000000000 0000000000000 00 000000000 00>0000000m

 

 

 

 

 

 

 

 

0

.0000 00 0000000 00000000uo0 .0000000 00 00 000000 00no0

m.m 0.0 0.0 0.0 0.0 0.0 1 00000000000
0000000000000 02
0.0 0.00 0.0 0.0 0.0 0.0 00.0 000100
0.0 0.0 0.0 0.0 0.0 0.0 0 0.0+:0.0 000 + 000100
0.0 0.0 0.0 0.0 0.0 0.0 0 0.0+m0.0 000 + 00020
0.00 0.0 0.0 0.0 0.0 0.0 00.0 00020
0.00 0.0 0.0 0.0 0.0 0.0 00.0 00020
0.00 0.0 0.0 0.00 0.0 0.0 00.0 000000000000
0.00 0.0 o 0.0 0.0 0 0.0+m0.0 000 +
000000000000

0.0 0.0 0.0 0.0 0.0 0.0 0 0.0+ 000 + m0:
0m.o+:0.0 100 + 0000000

0.00 m.0 m.0 0.0 0.0 0.0 0 0.m+ 000 + 00000000
m0.0+0m.m 10000 + 0000000

Amn\0xv
00>000 0003000 000000 000>000 0003000 000000 0000 000000009
100000 0000000 0000 100000 0000000 0000
00000000000 00000
100000000 + 000000000000 0000 0000000000000

 

0.0000
.00000002 .000000 000 00 00000 00000 00 000000000000 0000000000 000000000
10000 0000 000000000000 000 0000000000000 00 0000000 0000000 0003 00000> .0 00009 e

25

.m£\wx m>.m + w:.: an ¢oe + cowmmzq no nmpmfimcoo coameHaqam mvfiofinmms mocmemEmme mne

 

A.q Ednam Esacoaocmnov mumphmscmnsmq

 

 

 

 

 

n
.HHHx no Hoppcoo mpmHQEoouoa .HOApcoo on no mmsfiCfi ocuom
m.m 0.0 0.0 0.0 0.0 0.0 n soameHHgmm
mocmwhmsmumoa oz
o.oa o.oa m.a m.m w.m m.o :w.o
mm.H muzumm
o.oa w.m o.m m.m m.m ~.H AA m.m
+mm.mvm Hao + mmznmm
m.m o.od w.m o.oa m.m m.m q w.m+mm.o
q w.m+mH.H Hfio + momzm
m.m m.m o.H ~.m m.m m.o Arm.ovm momZm
o.oH 5.: m.m o.oa 5.: o.H zm.o
mm.a smnaficmecmzm
0.0H 0.: ~.H m.m ~.H o.H q m.m+mm.o HHo
A m.m+mH.H + EmQQHUmECmnm
m.m 0.0H m.H o.m m.m m.H AA w.m+ Hfio +
om.o+:m.mvm mpzumm + cONmpzm
0.0H m.m ~.H ~.m H.m m.H A m.m
+mm.o+:m.m
q m.m HHo + amnafluma
+mH.H+:m.m Icmna + coumhmm
Amg\mxv
mpmpprU Ummswfia magnCH mumppmSU Ummzwda abancfi mpmm ucmEpwmAB
ImnEMA poonomm mono Imnemq uoonnmm memo
mnemEpmmpp mocmwuwsmumoa mace mpcmEummgp
mansou + mocmwnmEmmpm mocmwpmSmpmoa mansoa
«.muma

.cmwfinofiz .mpcsoo mam CH mummn nmwsm cfi mcofipmcanEoo mocmwnmfimpmoq mansoc

mafia mocmwgmsmmaa cam mocmwnmEmpmoa mansoc mo mwcfipmp Hoppsoo Ummz adamfi>

.m manme

26

postemergence applications alone. This indicates that,
even though no visual toxicity to susceptible weeds was
seen, the preemergence treatment affected these plants

sufficiently to allow much greater phytotoxicity by the
postemergence herbicides.

Phenmedipham controled redroot pigweed as well as
many other broadleaf weeds in the cotyledonary and prior
to the full two-leaf stage (Table 1). Larger redroot
pigweed plants were not controlled by phenmedipham, but
activity was increased when pyrazon was added to the
postemergence mixture (Tables 2, 3, h, and 5) (2, 8).
EP-M75 controlled pigweed effectively at 0.8 kg/ha
(3/u lb/A) a.i. with a nonphytotoxic oil or 1.12 kg to
1.68 kg/ha (1 lb to 1.5 lb/A) or greater without an oil.

Mixtures of phenmedipham and EP-H75 can also be
used. Lower rates of SN503u, a 1:1 mixture of phenmedipham
and EP-M75, controlled many broadleaves, but higher rates
were necessary to control pigweed.

If the weeds had not emerged, a postemergence appli-
cation of a herbicide alone that does not exhibit soil
activity after application was not effective (Table 2).

A high amount of crop injury was observed with
herbicide combinations at Lenawee County in 1971 (Table 1).

With this amount of initial foliar inhibition, it seemed

 

Designation by Nor-Am Agricultural Chemicals,
Woodstock, Illinois.

27

possible that yields would be affected. However, an
analysis of variance performed on yields of various plots
showed there were no significant differences among the
mean yields (Table 6).

Also of concern was the effect of herbicides on the
recoverable sugar content in the root. As shown in Table
7, an analysis of variance indicated no significant
differences due to single or double applications of post-
emergence treatments combined with the preemergence
treatment.

It was advantageous to use combinations of preemer-
gence and postemergence herbicides to obtain the greatest
amount of weed control in sugar beets and not adversely
affect the yields of roots even though considerable foliar
injury results. Split applications of postemergence
herbicides gave excellent weed control. Sugar beet injury

and recoverable sugar content was not adversely affected.

28

Table 6. Yields of sugar beets in Lenawee County, Michigan,

 

 

1971.a
Postemergence
treatment Rate Mean Yield
(kg/ha) (lOOCvkg/ha)
Pyrazon + phenmedipham 2.2u+1.12 66-8
Pyrazon + phenmedipham
+ oil 2.2h+0.8u+3.8 L 60.5
Phenmedipham 1.12 59.1
Phenmedipham 1.68 66.3
SN503 1.12 70.1
SNSOB 1.68 59.6
EP-u75 1.12 73-0
EP-fl75 1.68 70.3
No postemergence
treatment - 67.6
Check — 67.4

 

8‘All above treatments, except the check, received a preemer-
gence application of pyrazon + TCA at 3.36 + 6.72 kg/ha.

The above means were not significantly different by an AOV
at the 5 percent level.

29

Table 7. Kilograms recoverable white sugar per 1000 kg of
sugar beet roots in Bay County, Michigan, 1972.

 

 

 

 

Postemergence
treatment Rate Weight
(ks/ha) (ks)
Receiving two_postemergence treatments
No postemergence application 150-5
Pyrazon + phenmedipham 2.24+l.l2+3.8 L
+ 011 2.2u+o.56+1.12 149.6
Pyrazon + EP-475 + 011 2(2.2u+o.56+1.12) 139.4
Phenmedipham + oil 1.12+l.12
0.56+l.12 146.5
EP-475 + 011 2(o.84+1.12) 153.4
Phenmedipham 1.68
0.84 138.3
EP-475 1.68
0.84 148.8
EP-475 0.84
0.84 143.1
SN503 0.84
0.84 148.9
SNSO3 1.68 147.4
SN503 1.68
0.84 151.8
SN503 + oil l.l2+l.12
o.56+1.12 140.0
SNSO3 + oil 1.68+1.12
0.8u+1.12 155.8
Receiving one postemergence treatment
Pyrazon + EP-475 + 011 2.2u+o.56+1.12 136-3
EP-475 + oil O.84+1.12 157-0
EP-475 + oil l.l2+l.12 150-0
EP-475 1.68 150-7
SN503 1.12 ' 145.6
SNSO3 1.68 146-2
SN503 + oil l.l2+l.12 140.2
SNSO3 + 011 1.68+1.12 149.5
Check - 154-5

 

aAll above treatments, except the check, received a pre-
emergence application of pyrazon + TCA at 4.48 + 6.72

kg/ha. The above means were not significantly different

by an AOV at the 5 percent level.

Literature Cited

Arndt, F. and C. Kotter. 1968. Zur selektivitat von
phenmedipham als nachauflaufherbizid in Beta-
ruben. Weed Res. 8:259-271.

Dexter, A. G. 1971. Weed control and crop injury from
herbicide combinations used in sugar beets. Proc.
North Cent. Weed Contr. Conf. 26:60.

Edwards, C. J. 1969. Experiments in the field perfor-
mance of phenmedipham. Proc. 9th Br. Weed Contr.
Conf. p. 575-579-

Holmes, H. M. 1969. Phenmedipham activity and selec-
tivity under U.K. conditions. Proc. 9th Br. Weed
Contr. Conf. p. 580-585.

Kossman, K. 1970. Uber abbaugeschwindigkeit und
verteilung von phenmedipham im boden, 1970. Weed
Res. 10:349-359.

Miller, D. and J. D. Nalewaja. 1973. Effect of
additives upon phenmedipham for weed control in
sugar beets. Weed Sci. 21:67-70.

Norris, R. F. 1973. Crystallization of phenmedipham
from aqueous emulsions. Weed Sci. 21:6-10.

Schweizer, E. E. and D. M. Weatherspoon. 1971.
Response of sugar beets and weeds to phenmedipham
and two analogs. Weed Sci. 19:635-639.

Sonawane, B. R. and C. O. Knowles. 1971. Phenmedipham

and mgaminophenol decomposition in alkaline soil.
Bull. Environ. Cont. Toxicol 6:322-327.

30

CHAPTER 3

Basis for Selectivity of Phenmedipham and EP-475
on Wild Mustard, Redroot Pigweed, and Sugar Beet

Abstract

Studies were initiated to determine the basis for selec-
tivity of phenmedipham (methyl-mfhydroxycarbanilate memethyl
carbanilate) and EP-475 (ethyl mrhydroxycarbanilate carbani—

late) on wild mustard [Brassica kaber (DC.) L.C. Wheeler

 

"pinnatifida" (Stokes) L.C. Wheeler], redroot pigweed

(Amaranthus retroflexus L.) and sugar beet (Beta vulgaris

 

L.) by evaluating spray retention, absorption, transloca-
tion and metabolism. Total photosynthesis in wild mustard
was severely inhibited in less than 5 hr after foliar
application of either herbicide and did not recover. Total
photosynthesis in sugar beet was slightly inhibited but
recovered during the observation period. Photosynthesis
in redroot pigweed recovered from a treatment of phenmedi-
pham but did not recover when treated with EP-475. There
were no differences observed in spray retention on the
leaf surfaces between the herbicides or among the species.
Differences in foliar absorption of the herbicide also
did not indicate why the herbicides differed in their
activity on redroot pigweed. Within 5 hr after herbicide
application, redroot pigweed had translocated more EP-475
than phenmedipham from the site of absorption. Within 5

hr after application, sugar beet had metabolized a large

31

32

amount of phenmedipham and EP-475, but wild mustard had
not. In this time redroot pigweed had metabolized a large
amount of phenmedipham but little EP-475. The key factor
explaining selectivity appeared to be at the initial
detoxication reaction of the parent compound as similar
amounts of various metabolites were found in all three

Species treated with each herbicide.

Introduction

 

The herbicides phenmedipham and EP-475 (Figure l) are
both applied postemergence to sugar beets for control of
many broadleaf and some grass weeds (1, 4, 6, 12). However,
only EP-475, an analog of phenmedipham, controls redroot
pigweed once it reaches the two leaf or older stage.

Phenmedipham and EP-475 both contain the peptide bond
structure common to many photosynthetic inhibitors (5, 11).

Phenmedipham has been shown to inhibit CO assimilation by

2
isolated chloroplasts from both susceptible and resistant
plants (1). However, with intact plants, the susceptible
plants did not recover from the initial inhibition of CO2
assimilation as did resistant plants1 (1, 9). Research

using isolated chloroplasts did not explain the basis for

 

lWillenbrink, J. 1969. The action of phenmedipham on
the CO fixation during photosynthesis in young sugar beet
leaves. Scientific and practical experience in using
phenmedipham for weed control in beets, Berlin, January
1969. Abstr. (of conf. sponsored by) Schering AG. 1969,
7-9.

33

.1000000o
emeafiemeemnd 000 Adopv masnmm

.HO whfipodhum .HMHSOGHOE

.H mmswfim
Emnmaooeconm
mmo -
OIZIQIOI IZIQIOIMmo
m o m o
meanmm

\J
G 12-0-0: fi\ -zuouoummo-mm0

m 0 m o

34

selectivity of these herbicides on certain plant species (3).
Kassebeer2 (7) found that the greater part of the phenmedi-
pham applied had been absorbed into plants 4 hr after
treatment. Only acrOpetal movement from the site of appli-
cation was observed, and this was evident within 8 hr after
treatment. In wild mustard, a rapid distribution through-
out the plant was observed. Bischof (2) found that sugar
beet and white mustard (Brassica hirta Moench) absorbed
similar amounts of foliar-applied phenmedipham.

Sugar beet, and redroot pigweed to a lesser degree,
rapidly metabolized phenmedipham to less toxic compounds
(7). EP-475 was also metabolized in sugar beet in time
(8). Bischof (2) found that neither uptake nor rate of
degradation alone explained the selectivity of phenmedipham
but rather a combination of the two factors producing a
high or low amount of active ingredient in the plants.

The purpose of this research was to find the basis
for selectivity of phenmedipham and EP-475 in sugar beet,
redroot pigweed, and wild mustard by evaluating spray
retention, absorption, translocation and metabolism. The
latter specie is susceptible to both compounds, whereas

redroot pigweed is susceptible to only EP—475.

 

2Kassebeer, H. 1969. The absorptioB, translocation
and decomposition of phenmedipham markedl C and 3H in young
beets (Beta vulgaris) and weeds. Scientific and practical
experience in using phenmedipham for weed control in beets,
Berlin, January 1969. Abstr. (of conf. sponsored by)
Scherling AG. 1969, p. 15.

35

Materials and Methods

Four pigweed plants, or three to four mustard plants,
or four sugar beet plants per 909-m1 cup were grown in
greenhouse soil until the plants had eight, six, and four
leaves, respectively. The plants were grown in the growth
chamber at 25 C in light of 24,000 to 27,000 lux with 16
hr of day-length. Photosynthesis and respiration measure-
ments were made by placing the cup of plants one at a time
in a sealed clear plastic test chamber (Figure 2) which in
turn was located in a growth chamber similar to that in
which the plants were grown, and attaching the test chamber
to a Beckman Model IR215 CO2 infrared gas analyzer by means
of TygonR tubing. Air from a compressed air source was
passed through the chamber at a rate of 500 cc per min.

Results were recorded on the Beckman Ten-Inch Laboratory
Potentiometric Recorder. VThe analytical system was adjusted
to zero on the recorder with nitrogen and to 50% deflection
with compressed air without plants in the chamber. The
plants were then placed in the plastic test chamber, the
lights were turned on which permitted the plants to photo-

synthesize, thereby lowering the CO content of the effluent

2
gas, until the recorder gave a straight horizontal line
response which indicated that equilibrium had been obtained.
The lights were turned off allowing the plants to respire.
This increased the CO2 content of the effluent gas until

again the recorder gave a straight horizontal line response.

36

Figure 2.

Sealed plastic chamber used for photosynthesis
and respiration studies.

 

_.1 _‘__——~_____4___

   

1.0

a. I , 1

... . I I

.r:

 

_ _ ..
....a aim-25.. . ____—==

 

ll)..||ll.lJ.)

38

One unit of change on the recorder paper was equivalent

to 6.46 mg of CO2 per min (Appendix A). Measurement on
these plants was taken prior to treatment and 4, 30, 45,
and 85 hr after treatment. Plants were sprayed topically
in a "movable boom" spray chamber with formulations of
either herbicide at 1.7 kg/ha in 280 L/ha of water and 2.1

R 80041:)3 nozzle tips.

kg/sq cm at 4.8 km/hr with TeeJet

' After the 85 hr observation, the leaves of the plants
were removed and stapled onto paper and photocopied. A
planimeter was used to obtain the leaf surface area from
the photocopy.

Retention of phenmedipham and EP—475 was studied by
spraying foliage of wild mustard, redroot pigweed, and
sugar beet with uniformly side-chain ring labelled l4C_
herbicide. Species were germinated and grown in greenhouse
soil in 909-ml cups in growth chambers at 25 C under conti-
nuous light with 24,000 to 27,000 lux. The cups were
randomized daily within the chamber. When sprayed, wild
mustard had three leaves, pigweed had five to six leaves
and sugar beet has two leaves. All treatments had three

replications. The lac-phenmedipham had a specific activity

0f 5.5 mCi/millimole and was 96% pure; 1“

C-EP-475 had a
specific activity of 1.95 mCi/millimole and was 98% pure.
Spraying was done as described above at the rate of 1.1

kg/ha ai of cold formulated herbicide spiked with 1 uCi

 

3Spraying Systems Company, Wheaton, Illinois.

39

(or 2 uCi in second experiment) of radioactive herbicide
per 100 ml of solution.

After application, the plants were allowed to dry and
then the leaves were removed and rinsed in 45 to 50 ml of
acetone for 15 sec to elute the herbicide from the leaf.
Leaf areas were obtained in the same manner as described
above. The amount of radioactivity obtained was determined
by Packard Tri-Carb Liquid Scintillation Spectrometer. The
scintillation solution used consisted of 0.1 g of 1,4-bis
[2-(4-methyl-5-phenyloxazolyl)J-benzene (dimethyl-POPOP),
5.0 g of 2,5-diphenyloxazole (PPO), 50.1 g of naphthalene,
380 m1 of toluene, 380 ml of 1,4-dioxane, and 240 ml of
absolute ethanol.

Translocation of these two herbicides in the three
species was studied by using ll‘C-—herbicides foliarly applied
into lanolin rings. The species were germinated in vermi—
culite and transplanted into #7 white quartz sand in 909-ml
cups at the cotyledon stage. These cups were watered
subterraneally with full—strength Hoagland's solution. The
growth chamber environmental conditions were 25 C under
continuous light at 24,000 to 27,000 lux. The cups were
randomized daily within the chamber.

When treated, wild mustard had four to six leaves,
pigweed had six to eight leaves and sugar beet had two
leaves. A 5 to 6-mm diameter lanolin ring was centered
at the basipetal end of the second oldest leaf on each

of two replications. A 5—ul drop containing 0.1 uC of

 

 

Illlll I]! I'll,
Illll’ll’ \llll: 111' III:

40

the radioactively labelled herbicide was placed into the
lanolin ring, allowed to dry, and the plants returned to

the growth chamber. The radioactive herbicides were
dissolved in EP-475 solvent system“: water (l:20,v/v)(10).
After each time period of l, 3, or 6 days after application,
the lanolin ring was removed, roots washed free of sand

and the intact plants freeze-dried. These plants were then
mounted onto white absorbent paper and radioautographed
using Kodak No-screen X-ray film.

To determine the type of distribution of the herbicides
within the plants, a root uptake study was done. The species
were germinated in vermiculite and transplanted into #7
white quartz sand at the cotyledon stage in the growth
chamber. The plants were watered subterraneally with full-
strength Hoagland's solution. The environmental conditions
used throughout were 25 C under continuous light at 13,000
to 16,000 lux. When wild mustard was in the four leaf
stage, pigweed in the six leaf stage, and sugar beet in
the two to four leaf stage, the plants were washed free
of sand and transferred into 20 x 80 mm vials containing
10 m1 of l/2-strength Hoagland's solution. The plants
were supported by a foam rubber stopper. After equilibra-
tion for 24 hr in the growth chamber, this solution was

replaced with 10 m1 of l/2-strength Hoagland's spiked with

 

“Supplied by Nor-Am Agricultural Chemicals, Woodstock,
Illinois.

41

l uC of either radioactively labelled herbicide per 200 m1

of solution and replaced in the growth chamber. Twelve

hr later the plants were taken out of the vials, roots

washed twice in distilled water, mounted onto white absorbent
paper, and radioautographed.

Studies on absorption and metabolism of these compounds
by the three species mentioned were conducted in the growth
chamber. The three species were germinated and grown in
greenhouse soil in 909-ml cups in the growth chamber at 25 C
in continuous light of 13,000 to 16,000 lux. At the same
stage as above, 0.1 uC of each labelled herbicide was applied
to the second oldest leaf of each species into a 7 to 8-mm
ink-marked ring centered at the basipetal portion of the
leaf. Care was taken not to allow spreading of the applied
droplet outside of the ink ring. There were three repli-
cations per treatment.

After 5 and 24 hr, the treated leaf was removed and
three types of extractions made. The area of the treated
leaf that was acropetal to the point of application was
cut off and designated as "tip". The area within the
inked ring was cut out of the leaf, rinsed in acidified
acetone for 15 sec, and set aside, labelled as "spot".
Acidified acetone was prepared by adding 1 m1 of l N HCl
into 1 L of acetone. The acetone rinse was collected into
56-ml bottles, which should contain all ll‘C-labelled
herbicide that was not absorbed into the cellular tissue.

The spot and tip tissue each were homogenized in a Sorvall

1:2

Omni-Mixer for 2 min in 15 ml of acidified acetone. The
homogenate was vacuum filtered through #5 filter paper
into 57-gm bottles and the collected residue weighted and
combusted by the Schoniger combustion method (13). The
three acetone-soluble leaf fractions collected from one
leaf were treated similarly in the rest of the procedure.
The bottles were flash-evaporated, chilled, and 200 ml of
cold methanol added. Of this, 50 ul was spotted onto 250
nm thick (20 by 20 cm) silica gel GF-254 (Brinkmann Instru-
ments) thin layer chromatography (TLC) plates developed in
chloroform: isopropylether (9:1,v/v)(hereafter called
solvent system I) and radioautographed. Any position,
except at that Rf equivalent to the parent material, on
the plate that exposed the X-ray was scraped from the
plate, eluted with methanol, filtered into 28-ml bottles,
dried by flash evaporation and chilled. Of the 200 ul of
methanol added to the bottle, 150 ul was spotted on similar
TLC plates as above and developed in a more polar solvent
system, butanol:water:acetic acid (12:5:3, v/v/v) (hereafter
called solvent system II) and then radioautographed. The
positions that were equivalent in Rf of the parent material
were scraped in liquid scintillation vials and radioassayed.
The TLC plates that were developed in the more polar
solvent system were delineated into four areas according
to the greater prominance of exposed areas to the X-ray
film, scraped into liquid scintillation vials, and radio-

assayed.

43

Results and Discussion

 

Phenmedipham and EP-475 application reduced the CO2
uptake of all three species within 4 hr after treatment
(Table 1). Total photosynthesis in wild mustard was greatly
reduced by both chemicals and did not recover within the
85 hr observation period. Sugar beet was not as adversely
affected and recovered with time. Total photosynthesis of
pigweed was greatly reduced but showed recovery in the plants
sprayed with phenmedipham but not in plants sprayed with
EP-475.

Arndt and Kotter (1) and Willenbrink5 also found that
phenmedipham inhibited photosynthesis in sugar beet, redroot
pigweed, and wild mustard but photosynthesis in sugar beet
and redroot pigweed recovered with time.

Dark respiration of phenmedipham-treated wild mustard,
redroot pigweed, and sugar beet and EP-475-treated sugar
beet was not reduced (Table 2). However, dark respiration
of EP-475-treated wild mustard and redroot pigweed was
reduced and did not increase with time. Arndt and Kotter
(1) found that dark respiration of wild mustard was per—

mantly inhibited by phenmedipham but sugar beet recovered

 

SWillenbrink, J. 1969. The action or phenmedipham on
the CO2 fixation during photosynthesis in young sugar beet
leaves. Scientific and practical experience in using phen—
medipham for weed control in beets, Berlin, January 1969.
Abstr. (of conf. sponsored by) Schering AG. 1969, p. 7-9.

1!:
'L,"

 

44

Table 1. Mean percent of initial total photosynthesis of

three species due to herbicide treatment.

 

Hours After Treatmenta

 

 

Herbicide
Species 4 30 45 85
Phenmedipham
Wild mustard *b 17.2 abc 12.7 abc 16.5 abc 23.3 00
Redroot
pigweed 33.3 d 49.0 e 52.9 e 71.6 f
Sugar beet * 83.9 fg 100.9 hi 99.6 hi 106.9 1
EP-475
Wild mustard * 17.4 abc 6.9 a 9.2 ab 14.2 abc
Redroot
pigweed 15.7 abc 4.4 a 5.1 a 22.5 bcd
Sugar beet * 79.8 fg 91.5 gh 83.8 fg 88.9 gh

 

aMeans followed by like letters are not significantly different

at the 5% level using Duncan's Multiple Range Test.

b

Asterisks indicate significance between the amount of photo-
synthesis prior to and 4 hr after herbicide treatment using
students "T" test.

45

Table 2. Mean percent of initial dark respiration of three
species due to herbicide treatment.

 

Hours After Treatmenta

 

 

 

 

Herbicide
Species 4 30 45 85
Phenmedipham
Wild mustard 69.6 a-e 61.1 a—d 57.5 abc 53.9 abc
Redroot
pigweed 86.6 d-i 91.8 e-i 97.1 r-1 111.6 hi i
Sugar beet 77.3 c—h 94.7 g-i 96.8 hi 106.1 1 L,
EP-475
Wild mustard *b 71.7 b-f 47.0 ab 55.5 abc 60.3 a—d
Redroot
pigweed * 74.0 b-g 59.0 a-d 41.8 a 55.2 abc
Sugar beet 87.8 e-i 90.4 e-i 104.0 i 92.8 e-i

 

aMeans followed by like letters are not significantly diff-
erent at the 5% level using Duncan's Multiple Range Test.
bAsterisks indicate significance between the amount of photo-
synthesis prior to and 4 hr after herbicide treatment using
Student's "T" test.

46

in time. Neither the effect of these herbicides on photo-
synthesis nor respiration explained the selectivity. A
decrease in photosynthesis can result from the closing of
the stomates. Using clear fingernail polish, impressions
of the lower surfaces of treated and untreated plants were
made and photographed (Figure 3). Observations over a
large area (1 sq cm) of the impressions indicated little or
no difference in stomate aperture.

There were no significant differences in the amount of
herbicide retained on the upper surfaces of leaves between
the two herbicides or among the three species (Table 3).

So this factor did not contribute to selectivity. At 5 hr
after treatment, there were no differences in the amount of
herbicide absorbed between the herbicides or among the species
(Table 4). At 24 hr after treatment, more phenmedipham was
absorbed by these plants, except for pigweed which absorbed
both chemicals in similar amounts. Bischof (2) also found
that sugar beet and white mustard absorbed phenmedipham in
similar amounts. The absorption of phenmedipham by redroot
pigweed and sugar beet and of EP-475 by wild mustard and
sugar beet had increased significantly between 5 and 24 hr
after application. Thus the plant species continued to
absorb herbicide during the time observed.

Once the herbicide has been absorbed, it may translocate
to other plant parts. Phenmedipham and EP-475 were not
translocated basipetally (Figure 4) from the point of

application, even 6 days after application (Figure 5).

47

 

Figure 3.

Microphotographs of lower leaf surfaces of
EP-475 treated wild mustard (A), redroot
pigweed (B), sugar beet (C); phenmedipham
treated wild mustard (D), redroot pigweed (E),
sugar beet (F); untreated wild mustard (G),
redroot pigweed (H), sugar beet (I).

 

49

Table 3. Amount of luC-herbicide retained on leaves of

three species.a

 

 

Herbicide Species DPM/6.5 sq cm

Phenmedipham Wild mustard 254
Redroot pigweed 292
Sugar beet 221

EP-475 Wild mustard 241
Redroot pigweed 285
Sugar beet 190

 

aThe above means were not significantly different by an
AOV at the 5% level.

50

Table 4. Absorption of 1L‘C-herbicides.

 

 

 

Herbicide Species Percent absorptiona
5 hr 24 hr

Phenmedipham Wild mustard 37.3 b 59.0 b
Redroot pigweed 22.4 ab *b 54.2 ab

Sugar beet 31.6 ab * 72.1 b

EP-475 Wild mustard 17.6 a * 39.2 a
Redroot pigweed 25.7 ab 39.1 a

Sugar beet 22.5 ab * 39.9 a

 

aMeans within a column followed by like letters are not
significantly different at the 5 percent level as determined
by Duncan's Multiple Range Test.

bAsterisks between two means indicates significance using
Student's "T" test.

51

Figure 4.

Translocation of luC-phenmedipham (C) and l4C_

EP-475 (D) in sugar beet (left), redroot pigweed
(center), and wild mustard (right) 1 day after
foliar application. The treated plants are at
top; the corresponding radioautographs are at
the bottom.

 

 

ah“ u.—

 

(“H-“'1‘
5
L -

 

 

53

 

Figure 5.

Translocation of luC-phenmedipham (A) and l4C_

EP-475 (B) in sugar beet (left), redroot pigweed
(center), and wild mustard (right) 6 days after
foliar application. The treated plants are at
top; the corresponding radioautographs are at
the bottom.

 

—__...._

 

 

55

However, there was acropetal translocation of both herbicides.
Kassebeer6 (7) observed that translocation of phenmedipham
was solely acropetal. A difference in the distribution of
the herbicides in the leaves can be seen when the herbicides
were supplied to the roots (Figures 6 and 7). There was
very little uptake of both herbicides in sugar beet, major
restriction to the major veins in pigweed, and a more
diffuse distribution in wild mustard.

Five hr after foliar application, wild mustard appeared 1

14

to translocate more C-herbicide acrOpetally from the point

 

of application than the sugar beet but the difference was
not statistically significant (Table 5). Redroot pigweed
did translocate significantly more EP-475 than phenmedipham.
Indications of higher amounts of EP-475 in redroot pigweed
could not be detected on the radioautographs due to the
veinal localization. There were no differences in the amount
of translocation between herbicides or among species 24 hr
after foliar application except that wild mustard continued
to acropetally translocate EP-475 in significant amounts
between 5 and 24 hr after application.

Of these amounts that did translocate acropetally within
the treated leaf, differences in amount of parent compound

metabolized can be seen 5 hr after foliar application (Table

 

6Kassebeer, H. 1971. Aufnahmegeschwindigkeit, metab-
olismus and verlagerung von phenmedipham bei verschieden
empfindlichen pflanzen. A. fur Pflanzenkrankheiten und
Pflanzenschutz 18:158—174.

56

Figure 6.

Distribution of root applied l[JO—phenmedipham

in wild mustard (left), redroot pigweed (center),
and sugar beet (right). The treated plants are

on top; the corresponding radioautograph is at
the bottom.

 

58

 

Figure 7.

Distribution of root applied luC-EP-475 in
wild mustard (left), redroot pigweed (center)
and sugar beet (right). The treated plants

are on top; the corresponding radioautograph
is at the bottom.

 

60

 

 

 

Table 5. Percent of 1“C from abSorbed herbicide translocated
acropetally in the same leaves of three species.
Percent l“C translocateda

Herbicide Species 5 hr 24 hr
Phenmedipham Wild mustard 22.3 ab 32.4 ab

Redroot pigweed 18.3 ab 28.1 ab

Sugar beet 10.7 a 33.0 ab
EP-475 Wild mustard 29.5 b *b 43.7 b

Redroot pigweed 57.7 c 36.5 ab

Sugar beet 21.2 ab 21.1 a

 

 

aMeans within a column followed by like letters are not
significantly different at the 5% level as determined by

Duncan's Multiple Range Test.

b
Students'

"T"

test.

Asterisks between two means indicate significance using

up

1 J"

61

6). Wild mustard did not metabolize as much phenmedipham
or EP-475 but sugar beet did.

As the three species metabolized both herbicides, com-
plexing with polar plant components was quick (Appendix B-l,
B-2, and B-3). Very small amounts of radioactivity was
found at Rf's other than those equal to the origin and
parent compound when the extracts were chromatographed in
solvent system I. Redroot pigweed metabolized large amounts
of phenmedipham but metabolized only small amounts of EP-475.
Metabolism of the herbicide continued between 5 and 24 hr
after application. Redroot pigweed had metabolized such
large amounts of phenmedipham 5 hr after application that
the increase in the amount metabolized 19 hr later was not
significantly different.

Kassebeer (7) had previously reported that sugar beet,
and redroot pigweed to a lesser degree, rapidly metabolized
phenmedipham. Knowles (8) found that foliarly applied
EP-475 was metabolized with time by sugar beet.

Much of the above metabolized material remained at the
origin of the TLC when chromatographed in the solvent system
I. When rechromatographed in the solvent system II, l4C_
labelled compounds were distributed as illustrated in
Figures 8 and 9. The ratio of the different metabolites
for each species within either time period were similar for
both herbicide treatments. So the ratio of various meta-

bolites was not a factor in the basis for selectivity.

If the ratio of various metabolites were similar and the

62

Table 6. Percent of translocated luC-herbicide metabolized

after 5 and 24 hr.

 

Percent metabolizeda

 

 

Herbicide Species 5 hr 24 hr

Phenmedipham Wild mustard 30.16 b *b 67.79 bc
Redroot pigweed 70.32 c 74.43 cd
Sugar beet 65.74 c * 83.28 d

EP-475 Wild mustard 12.81 a * 33.37 a
Redroot pigweed 17.61 b * 62.61 b
Sugar beet 67.06 c * 93.69 c

 

aMeans within a column followed by like letters are not
significantly different at the 5% level as determined by
Duncan's Multiple Range Test.

bAsterisks between two means indicates significance using
Students' "T" test.

 

63

Wild Mustard
50 I 5 hr 7’

"0 a 24hr

    

Pbramuage
oftxmal
'6

20

10

 

Hangman:
oftxmal

 

:imarlket

Peraamage
oftxmal

V

 

A B C D

Figure 8. Chromatographic separation of phenmedipham
metabolites using solvent system II. Rf
for A81.00-0.86; B=O.86-0.72; C=0.72-0.62;
D=0.62-0.49.

64

Wtklnmnand

 

SO'IShr

40

Pbraflumge
oftxmal

   

Panxmmflme
oftxmal

 

Shearlkmt

50 '
40

  

- 3O _

7

  
 

Penmwmage
oftxmal

10 V

 
 

A B C D

Figure 9. Chromatographic separation of EP-475 metabolites
using solvent system II. Rf for A=1.00-0.86;
B-O.86-0.72; C=0.72—O.62;D=0.62-0.49.

65

rates of possible changes between metabolites are similar,
the site of differential metabolism must be in the first
detoxication reaction involving the intact parent compound.
Selectivity of EP-475 and phenmedipham on redroot
pigweed can be explained by increased translocation and
decreased metabolism of EP-475. The metabolites acted in a
polar manner, which could be conjugates of polar plant

materials.

10.

11.

Literature Cited

Arndt, F. and C. Kotter. 1968. Zur selektivitat von
phenmedipham als nachauflaufherbizid in Beta-
ruben. Weed Res. 8:249-271.

Bischof, Von F., W. Koch, J. C. Majumdar, and F.
Schwerdtle. 1970. Retention, penetration, and
loss of phenmedipham related to varying factors.
Z. Pflanzenkrankheiten (Pflanzenpathologie)
Pflanzenschutz. Sonderh. V:95-102.

Buchel, K. H. 1972. Mechanisms of action and structure
activity relations of herbicides that inhibit
photosynthesis. Pest. Sci. 3:89-110.

Edwards, C. J. 1969. Experiments in the field perfor-
mance of phenmedipham. Proc. 9th Br. Weed Contr.

Conf., p- 575-579.

Good, E. 1962. Inhibitors of photosynthesis as herbi-
cides. World Review of Pest Cont. 1:19-28.

Holmes, H. M. 1969. Phenmedipham activity and selec-
tivity under U.K. conditions. Proc. 9th Br. Weed
Contr. Conf., p. 580-585.

Kassebeer, H. 1971. Aufnahmegeschwindigkeit, metabo-
lismus and verlagerung von phenmedipham bei versch-
ieden empfindlichen pflanzen. Z. fur Pflanzenkran-
kheiten und Pflanzenschutz 18:158-174.

Knowles, 0. and B. Sonawane. 1972. Ethyl mehydroxycar-
banilate carbanilate (EP-475) metabolism in sugar
beets. Bull. Environ. Cont. Toxicol. 8:73-76.

Kotter, C. and F. Arndt. 1968. Der Einfluss von phen—
medipham auf die CO -Aufnahme und die dunkelatmung
von zuckerruben und senf in Abhzngigkeit von
pflanzenalter. J. Int. Inst. Sugar Beet Res. 3:
126-133.

Norris, F. 1973. Crystallization of phenmedipham from
aqueous emulsions. Weed Sci. 21:6—10.

Schweizer, E. E. and D. M. Weatherspoon. 1971. Res-

ponse of sugar beets and weeds to phenmedipham and
two analogs. Weed Sci,19:635-639.

66

 

12.

13.

67

Van Overbeek, J. 1962. Physiological responses of
plants to herbicides. Weeds 10:170-174.

Wang, C. H. and D. L. Willis. 1965. Radiotracer
methodology in biological science. Prentice-Hall,
Inc., New Jersey, p. 363-364.

 

CHAPTER 4

Summary and Conclusions

Studies in the field and greenhouse were conducted to
evaluate the effect of phenmedipham and EP-475 on sugar
beet, redroot pigweed, and wild mustard. Areas of investi-
gation were efficacy in the crop and effects on yield and
sugar content in the field. The effect on photosynthesis
as related to spray retention, absorption, translocation,
and metabolism were studied in the laboratory.

The results of these investigations are summarized as
follows:

1. Combinations of preemergence and postemergence
herbicides were usually needed for effective weed control.

2. Crop injury resulting from herbicide combinations
did not affect final root yield.

3. No treatment affected the recoverable sugar content
of the sugar beet root.

4. Phenmedipham used as a postemergence herbicide will
control many common problem broadleaf weeds except redroot
pigweed in sugar beet fields.

5. EP-475 alone or in combination with phenmedipham
was necessary for redroot pigweed control.

6. At least 0.6 kg/ha (0.5 1b/A) of EP-475 was needed
to obtain the needed redroot pigweed control.

7. Photosynthesis in sugar beet, redroot pigweed, and

wild mustard was reduced within 5 hr after application of

68

69

either phenmedipham or EP-475 and the amount of reduction
and recovery was directly related to the susceptibility of
the specie.

8. There were no significant differences in spray
retention on the leaf surface between both herbicides or
among the species.

9. Differences in herbicide absorption did not help
explain the difference in activity of the two herbicides
on pigweed.

lO. Herbicide translocation was solely acropetal.

ll. Redroot pigweed translocated more EP-475 from the
site of application than phenmedipham.

12. Significant amounts of herbicide continued to be
translocated with time up to 24 hr after treatment.

13. Early distribution of both herbicides when root
applied was very diffuse in wild mustard and primarily
localized in the veins in redroot pigweed; however, sugar
beet leaves appeared to contain even less herbicide in the
primary veins than redroot pigweed.

l4. Differences in the rate of metabolism of the
parent compounds accounted for the difference in the
susceptibility of the species, the susceptible species did
not metabolize large amounts of herbicides quickly whereas
the resistant species did.

15. Since there was little differences in the ratio
of various metabolites between the two herbicides, the key
difference in metabolism was the initial detoxication reaction

involving the parent compound.

 

 

LIST OF REFERENCES

10.

LIST OF REFERENCES

Arndt, F. and C. Kotter. 1968. Zur selektivitat von
phenmedipham als nachauflaufherbizid in Beta-

ruben. Weed Res. 8:259-271. rm]

Bartha, R. and D. Pramer. 1967. Pesticide trans-
formations to aniline and azo compounds in soil.
Science 156:1617-1618.

Bischof, Von F., W. Koch, J. C. Majumdar, and F.
Schwerdtle. 1970. Retention, penetration, and I

 

loss of phenmedipham related to varying factors.
Z. Pflanzenkrankheiter (Pflanzenpathologie)
Pflanzenschutz. Sonderh. V:95-102.

Bordeleau, L. M. and R. Bartha. 1970. Azobenzene
residues from aniline-based herbicides; evidence
for labile intermediates. Bull. of Environ.
Cont. Toxicol. 5:34-37.

Brimhall, P. B., E. W. Chamberlain, and H. P. Alley.
1965. Competition of annual weeds and sugar beets.
Weeds 13:33-35.

Buchel, K. H. 1972. Mechanisms of action and structure
activity relations of herbicides that inhibit
photosynthesis. Pest. Sci. 3:89-110.

Chen, T. M., R. H. Brown, and C. C. Black. 1970. CO,
compensation concentration, rate of photosynthesis,
and carbonic anhydrase activity of plants. Weed
Sci. 18:399-403.

Chin, W. T., R. P. Stanovick, T. E. Cullen and G. C.
Hdkang. 1964. Metabolism of swep by rice. Weeds
12:201-205.

Dexter, A. G. 1971. Weed control and crop injury from
herbicide combinations used in sugar beets. Proc.
North Cent. Weed Contr. Conf. 26:60.

Dittert, L. W. and T. Higuchi. 1963. Rates of hydro-

lysis of carbamate and carbonate esters in alka-
line solution. J. of Pharm. Sciences 52:852-857.

70

11.

12.

13.

14.

15.

16.

17.

18.

19.

20.

21.

22.

71

Edwards, C. J. 1969. Experiments in the field per-
formance of phenmedipham. Proc. 9th Br. Weed
contra confo, p. 575-579.

El-Sharkawy, M. and J. Hesketh. 1965. Photosynthesis
among species in relation to characteristics at
leaf anatomy and CO2 diffusion resistance. Crop
Sci. 5:517-521.

Geiger, D. R. and D. A. Cataldo. 1969. Leaf struc-
ture and translocation in sugar beet. Plant
Phy81010 un:u5-5uo

Good, N. E. 1962. Inhibitors of photosynthesis as
herbicgdes. World Review of Pest Control
1:19-2 .

Herrett, R. 1969. In Kearney, P. C. and D. D. Kaufman
(eds.) Degradation of herbicides. Marcel Dekker,
Inc., New York, p. 113-145.

Hibbith, C. J. 1969. Growth and spray retention of
wild oat and flax in relation to herbicidal selec-
tivity. Weed Res. 9:95-107.

Holmes, H. M. 1969. Phenmedipham activity and selec-
tivity under U.K. conditions. Proc. 9th Br. Weed
Contr. Conf., p. 580-585.

James, C. S. and G. N. Prendeville. 1969. Metabolism
of chlorpropham (isopropyl m-chlorocarbanilate)
in various plant species. J. Agr. Food Chem.
17:1257-1260.

Kassebeer, Von H. 1971. Aufnahmegeschwin-digkeit,
metabolismus and verlagerung von phenmedipham
bei verschieden empfindlichen pflanzen. Zeits-
chrift fur Pflanzenkrankheiten und Pflanzenschutz
18:158-174.

Kearney, P. C. 1965. Purification and properties of
an enzyme reSponsible for hydrolyzing phenyl-
carbamates. J. Agr. Food Chem. 13:561-564.

Knowles, C. O. and B. R. Sonawane. 1972. Ethyl
m-hydroxycarbanilate carbanilate (EP-475) metabolism
in sugar beets. Bull. Environ. Cont. Toxicol.
8:73-76.

Korsmo, E. 1930. Unkrauter in ackerbau der neuzeit.
Translated and edited by H. W. Wollenweber.
Julius Springer, Berlin.

 

11

 

23.

24.

25.

26.

27.

28.

29.

30.

31.

32.

33-

72

Kossman, K. 1970. Uber abbaugeschwindigkeit und
verteilung von phenmedipham im boden, 1970.
Weed Res. 10:349-359.

Kotter, C. and F. Arndt. 1968. Der Einflub von phen-
medipham auf die COz-Aufnahme und die dunkelatmung
von zuckerruben und senf in Abhzngig keit von
pflanzenalter. J. Int. Inst. Sugar Beet Res.
3:126-133.

Mann, J. D., L. S. Jordan and B. Day. 1965. The
effects of carbamate herbicides on polymer synthe- '
sis. Weeds 13:63-65. I

Miller, S. D. and J. D. Nalewaja. 1973. Effect of
additives upon phenmedipham for weed control in 1
sugar beets. Weed Sci. 21_67-70.

 

Norris, R. F. 1973. Crystallization of phenmedipham T
from aqueous emulsions. Weed Sci. 21:6-10. f

Robertson, M. M. and R. C. Kirkwood. 1969. The mode
of action of foliage-applied translocated herbi-
cides with particular reference to the phenoxy-
acid compounds:II. The mechanism and factors
influencing translocation, metabolism and bio-
chemical inhibition. Weed Res. 9:94-120.

Robertson, M. M. and R. C. Kirkwood. 1969. The mode
of action of foliage-applied translocated herbi-
cides with particular reference to the phenoxy-
acid compounds:I. The mechanism and factors
influencing herbicide absorption. Weed Res.
9:224-240.

Schweizer, E. E. and D. M. Weatherspoon. 1971. Res-
ponse of sugar beets and weeds to phenmedipham
and two analogs. Weed Sci. 19:635-639.

Shadbolt, C. A. and L. G. Holm. 1956. Some quanti-
tative aspects of weed competition in vegetable
crOps. Weeds 4:111-123.

Shaw, W. C. and C. R. Swanson. 1953. The relation of
structural configuration to the herbicidal pro-
perties and phytotoxicity of several carbamates
and other chemicals. Weeds 2:43-65.

Sonawane, B. R. and C. O. Knowles. 1972. Phenmedi-
pham and m-aminophenol decomposition in alkaline
soil. Bull. Environ. Cont. Toxicol 6:322-327.

34.

35-

36.

37.

38.

39-

40.

41.

42.

43.

73

Sonawane, B. R. and C. O. Knowles. 1972. Comparative
metabolism of two carbanilate herbicides (EP-475
and phenmedipham) in rats. Pest. Biochem. and
Physiol. 1:472-482.

Stevens, 0. A. 1957. Weights of seeds and numbers
per plant. Weeds 5:46-55.

Still, G. 1968. Metabolism of 3,4-dichloropropionani-
lide in plants: the metabolite fate of the 3,4-
dichloraniline moiety. Science 159:992-993.

Still, G. G. and E. R. Mansager. 1971. Metabolism E a
of isoprOpyl 3-chlorocarbanilate by soybean plants. .
Jo Agr. FOOd Chemo 196879-88“.

Swalwell, J. G. 1971. Betanal E-lessons from 1971
spraying season. British Sugar Beet Review

40:87-89. J

Van Overbeek, J. 1962. Physiological responses of "
plants to herbicides. Weeds 10:170-174.

 

Wang, C. H. and D. L. Willis. 1965. Radiotracer
methodology in biological science. Prentice-Hall
Inc., New Jersey, p. 363-364.

Weatherspoon, D. M. and E. E. Schweizer. 1971. Com-
petition between sugar beets and five densities
of kochia. Weed Sci. 19:125-128.

Yih, R. Y., D. H. McRae and H. F. Wilson. 1968.
Metabolism of 3',4'dichlorOpropionanilide: 3,4—
dichloroaniline-lignin complex in rice plants.
Science 161:376-377.

Zimdahl, R. L. and S. N. Fertig. 1967. Influence
of weed competition on sugar beets. Weeds 15:
336-339-

APPENDICES

 

 

74

APPENDIX A

Method of recorder chart paper conversion to ug/COZ/min.

Compressed air flow rate 500 cc/min

CO2 content of compressed air 330 ppm or .033 percent

Molecular weight of CO 44

2
Standard volume 22.4 1/mo1e

22.4 1 contains 1 mole of gas

.5 l/min contains .0223 M (g/l) of gas/min
1 mole of gas contains .033 percent C02 -6
therefore .022 M/min contains 7. 59 x 10

or 7.359 x 10- x 44 = 3.23 x 10’ g COZ/min
or 3.23 mg CO /min 8R323 ug CO /min
therefore on geckman #101283 gecorder paper 1 unit
change = 6.46 ug CO2/min

M CO2/min

 

75
APPENDIX B-1

100

'II 5 hr
90' "24 hr

80,-
70 i

60

50 -

40

Percentage of Total

30

\\\\\\\\\\‘

20

   
 

10

O
[.1
M

100 .

III Suhr
80 224 hr

70 ‘
60

50 _

40 -

Percentage of Total

30 “
20

10

/’

   

0 1 2 3 P

'Chromatographic separation of labelled acetone soluble extracts
from phenmedipham (top) and EP-475 (bottom) treated wild mustard
using solvent system I. Rf for O(origin)=0.00-0.04; 1=0.04-
0.11; 2=0.11-0.20; 3=0.20-0.35; P(parent)= 0.35-0.48.

76
APPENDIX B-2

100

III 5 hr
9' 25324 hr

80

70
60

Percentage of Total

 

100

70
60-

50

40

Percentage of Total

30

20

\\\\W

10

     

O

0

l 2 3 P
Chromatographic separation of labelled acetone soluble extracts
from phenmedipham (top) and EP-475 (bottom) treated redroot
pigweed using solvent system I. Rf for 0(origin)-0.00-0.04;
180.04-0.11; 2=0.ll-0.20; 3=0.20-0.35; P(parent)=0.35—0.48.

77
APPENDIX B-3

100-

5 hr
90‘

80 “2“ hr

70-

60'

50-
40——

30 -

Percentage of Total

20~

10

 

100
90

4': U1
D" D‘
"3 "S

N.

80

7O
60

\\\\\\\\V

50

  

40-

Percentage of Total

30-
20-

10

0 1 2 3 P

Chromatographic separation of labelled acetone soluble extracts
from phenmedipham (tOp) and EP-475 (bottom) treated sugar beet
using solvent system I. Rf for 0(origin)=0.00-0.04; 1=0.04-O.1l;

2=0.11-O.20; 3=0.20-O.353 P(parent)=0.35-O.48.

 

-

0

ERS

 

MICIIWIWITIWKIUIWHVI H 4444er
3 1293 0301L 1434