5-(2,6-Difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-1, 2-isoxazoline as a useful rice herbicide

Article abstract of DOI:10.1021/jf051284f

5-(2,6-Difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-1, 2-isoxazoline derivative was synthesized, and its herbicidal activity was assessed under glasshouse and flooded paddy conditions. 5-(2,6-Difluorobenzyl) oxymethyl-5-methyl-3-(3-methylth

Full text of DOI:10.1021/jf051284f

J. Agric. Food Chem. 2005, 53, 8639−8643 8639
5-(2,6-Difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-
1,2-isoxazoline as a Useful Rice Herbicide
IN TAEK HWANG,* HYOUNG RAE KIM, DONG JU JEON, KYUNG SIK HONG,
JONG HWAN SONG, AND KWANG YUN CHO
Korea Research Institute of Chemical Technology, Yuseong, Taejon 305-606, Korea
5-(2,6-Difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-1,2-isoxazoline derivative was
synthesized, and its herbicidal activity was assessed under glasshouse and flooded paddy conditions.
5-(2,6-Difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-1,2-isoxazoline demonstrated good
rice selectivity and potent herbicidal activity against annual weeds at 125 g of a.i. ha-1 under
greenhouse conditions. Soil application of this compound showed complete control of barnyardgrass
to the fourth leaf stage at 250 g of a.i. ha-1. Field trials indicated that this compound controlled annual
weeds rapidly with a good tolerance on transplanted rice seedlings by postemergence and soil
application. This compound showed a low mammalian and environmental toxicity in various
toxicological tests.
KEYWORDS: Annual weeds; barnyardgrass; isoxazoline; sulfonylurea; toxicity
INTRODUCTION
controlling various kinds of weeds, while some of them lack
the ability to control gramineous weeds including barnyardgrass.
Instead of a sequential application, a premixture, “one-shot”
herbicide was quickly developed, which contained sulfonylurea
(i.e., bensulfuron-methyl, pyrazosulfuron-ethyl, or imazosulfur-
on), dominant in rice-planted areas, today. Also, the request
has been made for a new herbicide whose characteristics include
low environmental pollution or harmful effects, high activity,
low toxicity, high selectivity, and low persistence (5-8).
Throughout the world, rice is considered to be a major food
crop, especially in southeast Asia. The yield of rice is considered
to be significantly reduced when weeds are not controlled. In a
paddy, there are many weeds of various species such as annuals
and perennials and broad leaves and sedges, and the composition
of weeds changes, depending upon the climate, area, and soil
condition. Among various weeds, the barnyardgrass is noxious
in both transplanted and direct-seeded rice cultivation because
of its ecological similarity to rice. Many types of herbicides,
including soil- or foliar-applied herbicides, have been developed
and used to control barnyardgrass. Most of the herbicides can
control barnyardgrass at younger than 2 leaf stages with soil
application; however, older than 3 leaf stages of barnyardgrass
is hardly controlled with soil-applied herbicides. Differences
in ambient temperature in rice-growing areas may affect
barnyardgrass germination and growth rates, enabling the weed
to grow past the susceptible stage and escape control in some
areas (1-4).
Rice growers have been waiting anxiously for the introduction
of new potent herbicides that can selectively control annual and
perennial weeds, especially including the late stage of barn-
yardgrass by a 1-time application. Recently, highly active ALS
(acetolactate synthase or acetohydroxy acid synthase) inhibiting
herbicides have been developed and used worldwide, and their
formulations with a combination of various herbicides to control
barnyardgrass showed the ability of controlling all weeds in 1
time, called “one-shot” herbicides. It is the reason that these
ALS-inhibiting sulfonylurea herbicides are very effective in
5-Benzyloxymethyl-5-methyl-3-aryl-1,2-isoxazolines deriva-
tives were introduced in 1989 by BASF(Ref). These compounds
are known to have the herbicidal activity and selectivity to rice
with an unknown mechanism of action. A large number of
analogues have been reported in which various substituents
contain alkyl or benzene derivatives at the 3 position of
isoxazoline ring and substitution at the 5 position with methyl
or benzyloxymethyl groups. We focused on a new chemical
group, 5-(2,6-difluorobenzyl)oxymethyl derivatives and evalu-
ated the herbicidal performance of these isoxazoline derivatives
in a greenhouse. The compounds studied here have a novel 2,6-
difluorobenzyl oxymethyl group introduced at the 5 position
of the isoxazoline moiety (Figure 1). 5-(2,6-Difluorobenzyl)-
oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-1,2-isoxazo-
line exhibits an excellent herbicidal activity on barnyardgrass
with a wide application window from the pre-emergence up to
the 4th leaf stage and good crop compatibility to transplanted
rice (9-12).
The synthesis of a new isoxazoline derivative, its herbicidal
activity under greenhouse conditions, field trial for “one-shot”
herbicide, and its toxicological evaluation results are described
in this paper.
* To whom correspondence should be addressed. E-mail:
ithwang@krict.re.kr.
10.1021/jf051284f CCC: $30.25
© 2005 American Chemical Society
Published on Web 10/01/2005

8640 J. Agric. Food Chem., Vol. 53, No. 22, 2005
Hwang et al.
NO2S: C, 60.52; H, 5.08; N, 4.15; S, 9.50. Found: C, 60.53; H, 5.20;
N, 4.14; S, 9.43. UV λmax: 279.5 cm-1
Screening under Greenhouse Conditions. Three rice seedlings (cv.
Dongin) at 2.5 leaf stages were transplanted at a 2-cm depth in a pot
(surface area, 140 cm2) filled with muddy loam soil (clay, 14%; total
carbon, 1.5%; pH 5.6). Eight annual weed seeds were sown at 0.5∼1.0-
cm depths in the same pot. The pots were maintained under flooded
conditions at a 3-cm depth of water at 28-33 °C (day) and 20-26 °C
(night) in a greenhouse. The stock solution of test compounds in acetone
and water (50/50 by volume) was gently added to the water surface at
a prescribed rate of 5 days after transplanting. A total of 3 weeks after
the application, the herbicidal efficacy and rice injury was evaluated
on a visual scale of 0 (inactive or no damage) to 100 (complete kill of
weed or crop). Final results were presented as the average of triplicates.
Combination Experiment. Three rice seedlings (cv. Dongin) of 2.5
leaf stages were transplanted at a 3-cm depth in a pot (surface area,
500 cm2). A total of 10 annual and perennial weed species were sown
at 0.5∼1.0-cm depths in the same pot. The test compound and several
sulfonylurea in acetone were mixed and applied to the water surface at
13 days after seeding (DAS). A total of 3 weeks after the application,
the herbicidal activity was evaluated on a visual rating scale as described
above.
Field Trial. Field experiments were conducted in the year 2002 at
the experimental field in the Korean Research Institute of Chemical
Technology, Taejon, Korea. The soil was a silty to sandy loam soil
with a composition of 51% sand, 39% silt, and 10% clay. The content
of organic matter was 1.2%, and the pH of the soil was 5.9. The field
was rotavated and leveled in submerged conditions, and rice seedlings
(3 leaf stages, cv. Donjin) were transplanted with a transplanting
machine to an approximately 3-cm depth with 30-cm row spacing on
May 10th. To evaluate the herbicidal activity, the pregerminated seed
of annual weed species and rhizomes of perennial weeds were
additionally sown within each plot (2 × 3 m2). The test compounds
were formulated as granules (2/0.7% G, 600/21 g of a.i. ha-1) of the
following composition: test compound, 2.0/0.7 g; sodium tripolyphos-
phate, 2 g; sodium dodecylbenzene sulfonate, 0.1 g; talc, 30 g; and
bentonite, 65.2 g. The granule was dropped uniformly on the water
surface of the plot at a prescribed rate 15 days after transplanting the
rice seedlings. Rice injury was estimated by visual rating on a 0∼100
scale. Weed control at 45 days after application was determined as the
average of triplicates by the comparison of each weed species remaining
in the quadrat (0.5 × 0.5 m2) with those in the untreated.
Figure 1. Organic synthesis and chemical structures.
MATERIALS AND METHODS
Synthesis. Isoxazoline derivatives were synthesized as described in
our patent (12). Figure 1 described the final steps of the synthesis from
3-methyl-2-thiophene carboxaldoxime to 5-(2,6-difluorobenzyl)oxym-
ethyl-5-methyl-3-(3-methylthiophen-2-yl)-1,2-isoxazoline (compound
A).
3-Methyl-2-thiophenecarboxaldoxime. Freshly distilled 3-methyl-
2-thiophenecarboxaldehyde (126.0 g, 1.0 mol) was dissolved in ethanol/
water solution (200 mL/150 mL), and hydroxylamine hydrochloride
(76.5 g, 1.1 mol) was added during 15 min at 10-15 °C with good
stirring. A solution of NaOH (44.0 g, 1.1 mol) in water (50 mL) was
added dropwise to the reaction mixture, and it was stirred for an
additional 15 min at room temperature. The reaction mixture was
concentrated by rotary evaporation to precipitate white crystalline solids.
The precipitates were filtered and dried under vacuum to afford
3-methyl-2-thiophenecarboxaldoxime (139.0 g, 98.5%).
5-Hydroxymethyl-5-methyl-[3-(3-methylthiophen-2-yl)]-1,2-isox-
azoline. To a solution of 3-methyl-2-thiophenecarboxaldoxime (139.0
g, 0.98 mol) in DMF (300 mL) was added N-chlorosuccinimde (152.2
g, 1.14 mol) by potions for 45 min at 30-40 °C. After the reaction
mixture was stirred for an additional 1 h, it was poured into methylene
chloride (1000 mL). The solution was washed with aqueous 1 N HCl
solution (200 mL × 2) and brine (300 mL × 2), dried over MgSO4,
and filtered. The filtrate was placed in a 2-L round-bottomed flask,
and a mixture of 2-methylpropen-1-ol (86.6 g, 1.2 mol) and triethy-
lamine (118.0 g, 1.2 mol) was added to the mixture by dropping in a
funnel for 30 min at 5 °C. The reaction mixture was washed with brine
(200 mL × 2), dried over MgSO4, and concentrated by rotary
evaporation to give a pale yellow solid. A total of 50 mL of ethyl acetate
and 250 mL of hexane were added to the solids with good shaking,
and then, the suspension was cooled in an ice bath. The solid precipitates
were filtered and washed with hexane to give 5-hydroxymethyl-5-
methyl-3-(3-methylthiophen-2-yl)-1,2-isoxazoline as an ivory solid
(186.0 g, 90%).
Toxicology. Acute toxicity, genetic toxicity, and aquatic toxicity tests
were performed according to the OECD standard procedure (13-15).
LC50 data for compound A was obtained from a mouse for acute toxicity
and Oryzias latipes and Daphnia magna for aquatic toxicity. For genetic
toxicity test, stock solutions of these compounds were prepared by
dissolving the compounds in dimethyl sulfoxide. Chinese hamster lung
fibroblast (CHL) cells were maintained in minimum essential medium
supplemented with 5% fetal bovine serum (GIBCO BRL, Grand Island,
NY). Cells were harvested using 0.2% trypsin and seeded onto Ø 50-
mm culture dishes. The cells were then allowed to grow at 37 °C in a
5% CO2-95% air-humidified incubator.
5-(2,6-Difluorobenzyl)oxymethyl-5-methyl-3-(3-methyl-
thiophen-2-yl)-1,2-isoxazoline. To
a
solution of 5-hydroxy-
methyl-5-methyl-3-(3-methylthiophen-2-yl)-4,5-dihydroisoxazole (105.5
g, 0.5 mol) in DMF (400 mL) was added NaH (60% in mineral oil,
24.0 g, 0.6 mol) during 15 min at 40 °C, and the mixture was stirred
for 15 min at that temperature. A solution of 2,6-difluorobenzyl bromide
(124.0 g, 0.6 mol) in DMF (60 mL) was added to the reaction mixture
during 15 min, and the reaction temperature increased to 60-70 °C.
The reaction mixture was stirred for an additional 1 h at that temperature
and poured into ice water (500 mL). The solution was extracted with
ethyl acetate (500 mL × 2), and the organic layer was washed with 1
N HCl solution (200 mL × 2) and brine (200 mL × 2). The organic
layer was dried over MgSO4 and concentrated to form as oil. The oil
was purified by silica gel column chromatography (300 g, 1:20 ethyl
acetate/hexane), and the crude product was recrystallized in hexane to
give 5-(2,6-difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-
2-yl)-1,2-isoxazoline as a white crystalline solid (100.0 g, 60%). mp:
RESULTS AND DISCUSSIONS
Synthesis. As mentioned above, 5-benzyloxymethyl-1,2-
isoxazolines were described as herbicides and we discovered
that when we substituted R groups with phenyl or aminocarbonyl
groups (12). They showed good herbicidal activity against weeds
including barnyardgrass in paddy fields. Also, we substituted
various aromatic groups, furans, and thiophenes at the 3 position
in 5-benzyloxymethyl-1,2-isoxazoline and evaluated their her-
bicidal effects under submerged paddy conditions (12). Among
them, thiophene derivatives showed significant herbicidal activ-
ity under rice paddy conditions with good safety to the
transplanted rice. Various 5-benzyloxymethyl-5-methyl-3-
thiophenyl-1,2-isoxazolines were prepared from substituted
thiophenocarboxyaldoxime by several steps described above.
The modifications of substituents on the thiophene ring and
1
45-46 °C. H NMR (CDCl3) δ: 1.42 (s, 3H), 2.41 (s, 3H), 2.95 (d,
1H, J ) 16.5 Hz), 3.41 (d, 1H, J ) 16.5 Hz), 3.53 (dd, 2H, J ) 10.0,
15.9 Hz), 4.68 (s, 2H), 6.82-6.89 (m, 3H), 7.20-7.25 (m, 2H). MS
m/z (relative intensity): 338 (17.8), 337 (42.5), 180 (87.3), 137 (100),
127 (53.6). IR (KBr, cm-1): 3104.0, 2973.2, 2928.2, 2882.7, 1626.8,
1594.1, 1471.0, 1234.7, 1097.5, 1056.6, 786.0. Anal. Calcd for C17H17F2-

A Useful Rice Herbicide
J. Agric. Food Chem., Vol. 53, No. 22, 2005 8641
Table 1. Herbicidal Activity of Compound A on the Annual Paddy Weeds Treated at 5 DA(S)Ta
annual weed species
LIDPY ROTIN
87 100
rate (g/ha)
rice(TR)
ECHOR
SCPJU
MOOVA
ANEKE
CYPDI
LUDPR
1000
500
250
125
62.5
0
0
0
0
0
100
100
100
100
63
50
37
0
0
0
100
100
100
100
20
70
23
0
0
0
100
100
100
100
100
100
100
100
100
100
53
50
33
33
100
100
100
30
a DA(S)T, days after (seeding) transplanting; TR, transplanted rice; rice(TR), transplanting 2.5 leaf stages of rice seedlings; ECHOR, Echinochloa oryzicola; SCPJU,
Scirpus juncoides ROXB.; MOOVA, Monochoria vaginalis PRESL.; LIDPY, Lindernia pyxidaria L.; ROTIN, Rotala indica KOEHE.; ANEKE, Aneilema keisak HASSK.;
CYPDI, Cyperus difformis L.; LUDPR, Ludwigia prostrata ROXB. Results are evaluated 3 weeks after application by visual rating scales of 0−100.
5-benzyl ring were mainly performed. In general, isoxazolines
attached at the 2 position of thiophene ring showed better
herbicidal activity than those attached at the 3 position. In case
of 3-(thiophen-2-yl)-isoxazolines, 3 substituents such as methyl
and bromine in thiophene and the 5-(2,6-difluorobenzyl)-
oxymethyl group increased the herbicidal activity along with
the selectivity for rice (12).
Herbicidal Activity and Selectivity under Greenhouse
Conditions. Compound A, 5-(2,6-difluorobenzyl)oxymethyl-
5-methyl-3-(3-methylthiophen-2-yl)-1,2-isoxazoline, showed the
best results in herbicidal activity against paddy weeds and safety
to rice. This compound also showed good safety to transplanted
rice at 1000 g of a.i. ha-1 and potent herbicidal activity on
annual weeds, such as Echinochloa oryzicola, Monochoria
Vaginalis, Rotala indica, Cyperus difformis, and Ludwigia
prostrate, at a rate of 62.5∼125 g of a.i. ha-1 when applied at
5 days after transplanting (DAT). Even at the rate of 62.5 g of
a.i. ha-1, this compound showed complete control of Cyperus
difformis and Ludwigia prostrata tested. However, Scirpus
juncoides, Lindernia pyxidaria, and Aneilema keisak were not
controlled by this compound even at the rate of 1000 g of a.i.
ha-1 (Table 1).
Figure 2. Control values of compound A against the leaf stages of
barnyardgrass under greenhouse conditions.
This compound showed excellent control efficacy to 2 and 3
leaf stages (LS) of barnyardgrass at 62.5 g of a.i. ha-1; however,
250 g of a.i. ha-1 was required to control 4 LS of
barnyardgrass (Figure 2).
toxicity with an LC50 of 1.9 and 2.7 mg/L to Oryzias latipes
and Daphnia magna, respectively. They did not show any
harmful effects on the Chinese hamster lung fibroblast (CHL)
cells, being negative in both mutation and chromosome aber-
ration tests (Table 4). These results were sufficient toxicological
data for pesticide registration in Korea.
Combination Activity. As shown in Table 2, a combination
effect of compound A and five sulfonylurea herbicides was
evaluated against six annual and four perennial weeds in a pot
test under greenhouse conditions. All of these combinations were
safe to the transplanting rice and showed excellent weed control
activity to these weeds tested. A combination with bensulfuron,
cyclosulfamuron, halosulfuron, and azimsulfuron showed the
additive effect to the Echinochloa oryzicola. Aeschynomene
indica was also effectively controlled in the combination of
bensulfuron, but the combination of pyrazosulfuron showed an
antagonistic interaction to Scirpus juncoides. These results
showed that the 300 g of a.i. ha-1 of this compound was enough
for the purpose of these combinations.
Field Trial. The combination of compound A and pyrazo-
sulfuron (2/0.7%, 600/21 g of a.i. ha-1) granules showed
excellent weed control (g98%) efficacy against annual and
perennial weeds treated at 15 days after transplanting. The
reference of molinate/pyrazosulfuron (5/0.7%, 1500/21 g of a.i.
ha-1) granules also showed low injury and herbicidal activity;
however, the test compound showed better efficacy compared
to the reference (Table 3). This mixture induced slight injury
to the transplanting rices at 1200/42 g of a.i. ha-1, twice the
recommended rate.
In the recent year, many types of herbicides have been
introduced for selective control of annual weeds, especially
including the late stage of barnyardgrass and perennial weeds
as “one-shot” herbicides in paddy rice fields. Most of the
herbicides can control barnyardgrass at younger than 2 leaf
stages with soil application; however, older than 3 leaf stages
of barnyardgrass are hardly controlled with soil-applied herbi-
cides (1-3). We focused on the new chemical group, 5-ben-
zyloxymethyl-1,2-isoxazoline derivatives, and evaluated the
herbicidal performance of these isoxazoline derivatives in a
greenhouse and field trials. Among these compounds, 5-(2,6-
difluorobenzyl)oxymethyl-5-methyl-3-(3-methylthiophen-2-yl)-
1,2-isoxazoline was identified to have excellent efficacy on
barnyardgrass, being in wide growth stages from the 2 leaf to
4 leaf stage, and good crop compatibility to transplanted rice.
Also, we evaluated the herbicidal properties in soil and a
combination effect of this compound with sulfonylurea herbi-
cides as a one-shot herbicide. Furthermore, mammal toxicity
was investigated as informal methods.
Toxicity. Acute toxicity (LD50 data) of compound A to mice
was over 5000 mg/kg. This compound showed low aquatic

8642 J. Agric. Food Chem., Vol. 53, No. 22, 2005
Hwang et al.
Table 2. Combination Activity between Compound A and Several Sulfonylureasa
rate
(g/ha)
ORYSA
(TR)
herbicide
ECHOR
SCPJU
MOOVA
ANEKE
LUDRP
AESIN
SAGPY
ELOKU
SAGTR
CYPSE
com. A
+
+
+
+
+
PYR
0/21
300/21
600/21
0/51
300/51
600/51
0/60
300/60
600/60
0/54
300/54
600/54
0/15
10
0
0
0
0
0
0
0
10
20
10
10
0
100
100
100
60
100
100
60
100
100
90
100
100
95
100
100
50
50
50
60
60
50
50
50
50
50
70
60
60
100
100
80
90
90
90
90
90
90
80
90
90
90
90
80
100
100
100
60
40
40
100
100
100
60
100
100
100
100
100
90
100
90
90
90
90
80
80
80
100
100
80
100
90
70
80
100
30
70
70
70
50
70
60
70
70
60
60
70
70
60
50
60
95
100
100
90
100
100
90
100
100
100
100
100
95
90
80
80
80
80
80
90
80
60
80
90
90
80
80
80
100
98
98
95
95
95
100
95
com. A
com. A
com. A
com. A
BEN
CYC
HAL
HAL
70
100
100
100
100
100
100
100
90
90
100
100
100
100
100
100
300/15
600/15
0
0
100
100
100
100
95
100
90
a Herbicide was applied at 13 days after transplanting (TR). PYR, pyrazosulfuron; BEN, bensulfuron; CYC, cyclosulfamuron; HAL, halosulfuron; AZY, azimsulfuron.
Results are evaluated 3 weeks after application by visual rating scales of 0 100.
−
Table 3. Herbicidal Activity and Rice Injury of Compound A in Combination with Pyrazosulfuron under a Submerged Paddy Field
rice injurya
control value (%)
-
1
treatment
application (g of a.i. ha
)
R
D
ECHORb
other annualsc
perennialsd
totale
compound A/pyrazosulfuron (granule)
molinate/pyrazosulfuron (granule)
600/21
1500/21
10
10
30
20
98.8
95.9
98.3
94.5
97.9
96.5
98.3
95.6
a Rice injury, transplanted rice at three leaf stages of seedling; rice injury, where 0 indicates no visible effect and 100 indicates complete death of plants. R, recommended
rate; D, double rate. b ECHOR, Echinochloa oryzicola. c Other annuals included Scirpus juncoides, Monochoria vaginalis, Lindernia pyxidaria, Rotala indica, Aneilema
keisak, Cyperus difformis, and Ludwigia prostrata. d Perennials included Cyperus serotinus, Sagittaria pygmaea, Eleocharis kuroguwai, and Sagittaria trifolia. e Total means
the average control values of ECHOR, other annuals, and perennials.
LITERATURE CITED
Table 4. Toxicological Data for Compound A
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genetic
toxicity
aquatic
toxicity
acute toxicity
mouse
chromosome
aberration test
Oryzas
latipes
Daphnia
magna
mutation
negative
compound A
>5000 mg/kg
negative
1.9 mg/L
2.7 mg/L
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C.; Kim, K. U. Ecology of weed occurrence and establishment
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(7) Hwang, I. T.; Hong, K. S.; Choi, J. S.; Kim, J.-S.; Yu, J. H.;
Ko, Y. K.; Ryu, J. W.; Chang, H. S.; Kim, D.-W.; Cho, K. Y.
Herbicidal and biological characteristics of a new benzenesulfo-
nylurea compound, K-11451, under submerged paddy condition.
Pestic. Sci. 1999, 55, 578-580.
In transplanting rice cultivations, herbicide application has
been usually carried out around 10 days after transplanting. It
is the reason for securing rice safety from herbicidal crop injury.
However, many kinds of weeds might have occurred and grew
up to 2 leaf stages of seedlings during these periods. This
compound showed good safety to transplanted rice at 1000 g
of a.i. ha-1 and herbicidal activity to the aged barnyardgrass.
These advantages were more active and valuable to rice
cultivation as a one-shot herbicide. It is the reason of sulfonyl-
urea herbicides that is very effective in controlling various kinds
of weeds other than gramineous weeds, including barnyardgrass.
A combination effect with several sulfonylurea herbicides was
safe to the transplanting rice and showed excellent weed control
activity to annual and perennial weed species. It is suggested
that these results might have a good possibility for developing
a mixture with sulfonylurea herbicide as a one-shot herbicide
for rice cultivation.
In conclusion, 5-(2,6-difluorobenzyl)oxymethyl-5-methyl-3-
(3-methylthiophen-2-yl)-1,2-isoxazoline will be selected as the
most useful herbicide in paddy rice from the results of the pot
tests in a greenhouse. Its excellent herbicidal performance has
also been confirmed in field trials and by investigation of its
mammalian toxicity.
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