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FORMESAFEN
CASRN: 72178-02-0
For other data, click on the Table of Contents
Human Health Effects:
Skin, Eye and Respiratory Irritations:
Mild skin irritant; mild to moderate eye irritant (rabbits).
Probable Routes of Human Exposure:
Occupational exposure to fomesafen may occur through inhalation of spray mists
and aerosols and dermal contact with this herbicide during or after its application
or at workplaces where fomesafen is produced. (SRC)
Emergency Medical Treatment:
Animal Toxicity Studies:
Non-Human Toxicity Excerpts:
In the present paper we describe needle-shaped and granular cytoplasmic inclusions
in the liver cells of mice and rats with experimental porphyria biochemically
resembling human porphyria cutanea tarda. The inclusions were inconspicuous
in routine histological slides. The ferric ferricyanide reduction reaction,
however, enabled us to demonstrate their shape and location within the hepatic
lobule. Needle-shaped inclusions are considered to represent a structure specifically
seen in experimental porphyrias resembling porphyria cutanea tarda. These structures
are similar to the inclusions seen in human porphyria cutanea tarda.
The results of quantitative structure-activity relationship (QSAR) analysis
on a structurally diverse group of peroxisome proliferators are reported. The
relative potencies of 11 peroxisome proliferators (with respect) to clofibric
acid) for induction of palmitoyl-CoA oxidation in rat hepatocyte cultures appear
to be determined by a combination of lipophilicity (logP descriptor) and calculated
binding affinity (logK) to a model of the mouse liver peroxisome proliferator-activated
receptor alpha (mPPARalpha) ligand-binding domain. It is possible that desolvation
of the putative binding site and ligand ionization may also play a role in activation
of the mouse liver peroxisome proliferator-activated receptor alpha.
Field studies were conducted to determine rhizomatous johnsongrass and barnyardgrass
control with clethodim, quizalofop-P-ethyl, fluazifop-P, sethoxydim, fenoxaprop-ethyl,
and quizalofop-P-tefuryl applied alone and with lactofen, imazaquin, chlorimuron,
and formesafen. Graminicides applied alone controlled johnsongrass and barnyardgrass
83 to 99%. Of the graminicides evaluated, clethodium was the most antagonistic
of the broadleaf herbicides toward the activity of graminicides. Clethodim mixed
with imazaquin reduced johnsongrass control as much as 64% and mixed with chlorimuron
reduced barnyardgrass control as much as 52%. Quizalofop-P-tefuryl was least
affected by broadleaf herbicides and formesafen was least antagonistic in mixtures
with graminicides.
The effect of the protoporphyrinogen oxidase-inhibiting herbicide formesafen
on liver porphyrin accumulation was studied in long-term high-dose experiments.
Formesafen caused liver accumulation of uroporphyrin and heptacarboxylic porphyrin
when fed at 0.25% in the diet to male ICR mice for 5 mos. (Formesafen-treated
mice: 52 nmol uroporphyrin, 21 nmol heptacarboxylic porphyrin/g liver; control
mice: traces of uroporphyrin, heptacarboxylic porphyrin not detected). Uroporphyrinogen
decarboxylase activity was depressed to about 25% of control values. Iron treatment
accelerated the development of this porphyria cutanea tarda-like experimental
porphyria both in ICR and C57B1/6J mice. In contrast to other uroporphyrinogen
decarboxylase inhibitors, formesafen treatment did not increase the cytochrome
P450IA-related activities and the amount of P450IA2 protein was shown to be
significantly decreased by Western immunoblotting. Thus, formesafen is a unique
chemical that inhibits both the oxidation of protoporphyrinogen as well as the
conversion of uroporphyrinogen to caproporphyrinogen. However, the accumulation
of highly carboxylated porphyrins is evident only after prolonged treatment
with high doses of the herbicide.
One important factor which may influence the extent and rate of percutaneous
absorption is the dosing vehicle. The purpose of the experiments described was
to compare the effect of dosing vehicles of different polarities on the absorption
of two herbicides across rat skin in vivo. Rats were dosed dermally with either
fluazifop-butyl (logP(oct) 4.5) or formesafen sodium salt (logP(oct) -1.2) in
propylene glycol (PG), octanol (OCT), or ethyl decanoate(ED), and the amount
of radioactivity excreted in urine was determined. Absorption rates were estimated
from the urinary excretion data and from blood kinetic data derived from intravenously
dose rats. For fluazifop-butyl the average rate of absorption (x10(-2) ug/hr-1
+/- SE) was not greatly influenced by the dosing vehicle (octanol, 2.94 +/-
0.08; ethyl decanoate 3.66 +/- 0.10; propylene glycol, 3.95 +/- 0.32) despite
relatively large differences in solubility (propylene glycol, 38 mg/ml; octanol,and
ethyl decanoate, > 600 mg/ml). These results were consistent with the finding
that there was at most only a twofold difference in the epidermal membrane:vehicle
partition coefficients (km). In contrast, the absorption rate of formesafen
from propylene glycol (1.98 +/- 0.04) was approximately half that of ethyl decanoate
(3.98 +/- 0.06) and octanol (4.49 +/- 0.08) for the first 30 hr after application
and was in keeping with solubility data (propylene glycol, 638 mg/ml; octanol,
12 mg/ml; ethyl decanoate, < 10 mg/ml). At later time points the absorption
of formesafen from propylene glycol increased; this is discussed in relation
to the penetration-enhancing properties of propylene glycol.
Carryover potential of imazaquin (0.14 kg ai/ha), chlorimuron plus metribuzin
(0.06 + 0.36 kg/ha), and formesafen (0.28 kg/ha) to snap bean, watermelon, cucumber,
mustard, and sunflower was evaluated in Arkansas in 1987 to 1989. Crops were
direct-seeded into treated plots at various times after application. Imazaquin
and chlorimuron plus metribuzin injured sunflower, watermelon, cucumber, and
mustard when planted 16 wk following application in one of two years. Formesafen
injured all crops initially but did not injure snap bean, sunflower, watermelon,
and cucumber planted 16 wk after application. In experiments in which herbicides
were applied to soybean, fall-planted spinach and mustard were injured in one
of two years.
The effects of the herbicides formesafen oxyfluorfen, oxadiazon, and fluazifop-butyl
on porphyrin accumulation in mouse liver, rat primary hepatocyte culture and
HepG2 cells were investigated. Ten days of herbicide feeding (0.25% in the diet)
increased the liver porphyrine in male C57B1/6J mice from 1.4 +/- 0.6 to 4.8
+/- 2.1 (formesafen) 16.9 +/- 2.9 (oxyfluorfen) and 25.9 +/- 3.1 (oxadiazon)
nmol/g wet weight, respectively. Fluazifop-butyl had no effect on liver porphyrin
metabolism. Formesafen, oxyfluorfen and oxadiazon increased the cellular porphyrin
content of rat hepatocytes after 24 hr of incubation (control, 3.2 pmol/mg protein,
formesafen, oxyfluorfen and oxadiazon at 0.125 mM concentration 51.5, 54.3 and
44.0 pmol/mg protein, respectively). The porphyrin content of HepG2 cells increase
from 1.6 to 18.2, 10.6 to 9.2 pmol/mg protein after 24 hr incubation with the
three herbicides. Fluazifop-butyl increased hepatic cytochrome P450 levels and
ethoxy- and pentoxyresorufin O-dealkylase (EROD and PROD) activity, oxyfluorfen
increased pentoxyresorufin O-dealkylase activity. Peroxisomal palmitoyl CoA
oxidation increased after formesafen and fluazifop treatment to about 500% of
control values both in mouse liver and rat hepatocytes. Both rat hepatocytes
and HepG2 cells can be used as a test system for the porphyrogenic potential
of photobleaching herbicides.
1. The three-dimensional structure of a portion of the ligand-binding domain
of the mouse liver peroxisome proliferator-activated receptor (PPAR) described
by Issemann and Green (1990) has been modelled from amino acid sequence data.
2. By inspection of the three-dimensional structure of the portion of the peroxisome
proliferator-activated receptor ligand-binding domain, a putative binding site
for peroxisome proliferation, consisting of one isoleucine, one lysine and two
phenylalanine moieties (residues 354, 358, 359 and 361, respectively), has been
identified. 3. The interaction of 12 peroxisome proliferators with the putative
peroxisome proliferator-activated receptor binding site has been investigated
and energetics of binding calculated from ligand-bound and ligand-free receptor
geometries. 4. The interaction data have been used to establish quantitative
structure-activity relationships (QSARs) between peroxisome proliferator binding
and either peroxisome proliferator-activated receptor activation in COS1 cells
or induction of palmitoyl-CoA oxidation in rat hepatocyte cultures. 5. The results
are discussed in terms of the role of peroxisome proliferator-activated receptor
in the mechanism of initiation of peroxisome proliferation in rodent liver.
Two field experiments were established in 1988 and 1989 in southeast Missouri
to evaluate several herbicides and herbicide combinations for giant ragweed
control in soybean. In 1988, a timely rainfall was not received for soil-applied
herbicides and giant ragweed control was less than 75%. However, in 1989 soil
moisture was sufficient for uptake of soil-applied herbicides and early season
giant ragweed control was generally greater than 80%. Chlorimuron, chlorimuron
plus 2,4-DB, (4-(2,4-dichlorophenoxy)butanoic acid) imazaquin plus 2,4-DB, acifluorfen
followed by naptalam plus 2,4-DB, formesafen, and imazethapyr applied to 2.5
to 5 cm giant ragweed controlled more than 85% in 1988. In 1989, all POST treatments
except imazaquin controlled more than 8.1% of giant ragweed 2 wk after treatments.
Imazethapyr controlled seedling giant ragweed at heights up to 12-25 cm. Giant
ragweed regrowth and/or reinfestation and giant ragweed seed production occurred
with all herbicide treatments.
Field studies were conducted from 1986 through 1988 to evaluate various herbicides
for yellow nutsedge control and peanut yields. Three applications of pyridate
provided control comparable to two applications of bentazon with yellow nutsedge
regrowth beginning 3 to 4 wk after application depending on moisture conditions.
Crop oil concentrate did not improve the activity of pyridate. Flurtamone provided
control comparable with that of metolachlor. Nutsedge control with formesafen
was erratic with peanut injury noted. peanut yields did not reflect the competitive
nature of nutsedge.
Field studies were conducted at three locations in Louisiana (USA) over two
years to evaluate mid-season, foliar-applied acifluorfen, formesafen, and lactofen
for hemp sesbania control in soybean. Acifluorfen and formesafen were applied
POST at 30, 40, 50, 60, 70, 140, and 280 g ai/ha. The data fit a quadratic model
and log transformations were made to determine differences between treatments.
Hemp sesbania control was highly correlated with herbicide rate for each herbicide.
Averaged over rates of application, acifluorfen, and formesafen provided equivalent
control of hemp sesbania, which was greater than that achieved with lactofen.
The minimum effective rate of acifluorfen or formesafen for 80 and 100% control
of 50- to 60-cm hemp sesbania was 50 and 140 g ai/ha, respectively. The minimum
effective alctofen rate to provide at least 80% control was 220 g/ha.
Field studies were conducted to identify herbicides suitable for improved
control of hairy nightshade, redroot pigweed, and common lambsquarters in pinto
beans. Formesafen at 0.25 kg ai/ha did not adequately control these weeds. Clomazone
at 0.5 kg ai/ha controlled common lambsquarters but only suppressed the growth
of redroot pigweed and hairy nightshade. Ethalflurlin at 0.8 to 1.1 kg ai/ha
gave excellent initial control of these weeds but did not control later flushes
of hairy nightshade. Imazethapyr applied PPI or POST at 50 to 75 g ai/ha controlled
hairy nightshade, redroot pigweed, and common lambsquarters throughout the growing
season. Imazethapyr combined with ethalfluralin gave superior weed control and
resulted in greater yields than the most commonly used herbicides in pinto beans
in western Canada.
Research was conducted to determine the tolerance of flue-cured tobacco to
formesafen and the potential for weed control in tobacco with formesafen. Treatments
consisted of formesafen at 0.4 or 0.6 kg ai/ha applied pretransplant incorporated
(PTI), pretransplant (PRE-T), post-transplant (POS-T), postemergence over-top
(POT), or post-directed (PD). Tobacco injury within 30 days of application was
as high as 30%, but tobacco recovered and few significant differences in tobacco
yield, grade index, or prices were observed except where formesafen was applied
pretransplant incorporated at 0.6 kg/ha. Tobacco tolerance relative to time
of application was generally pretransplant = postemergence over-top > post-transplant
= pretransplant incorporated. Florida pusley and large crabgrass control was
> 80% for all formesafen treatments. Yellow and purple nutsedge control was
approximately 30% before cultivation.
The postemergence-active herbicides lactofen, formesafen, and acifluorfen
were applied to established matted-row strawberry plants (Fragaris x annanassa)
and evaluated for broadleaf weed control and foliar phytotoxicity. Strawberries
were evaluated for yield and fruit quality. Treatments were applied following
June renovation. All herbicide treatments resulted in acceptable control of
broadleaf weeds present at the time of application; however, sicklepod (Cassia
obtusifolia) germinated after herbicide application. All treatments caused foliar
development. Formesafen and acifluorfen were the only herbicides to suppress
runner count. Yield the following year were not reduced by herbicide treatments.
The response of crop and weed species to herbicides within the same family
may vary considerably. The detrimental effect of late seedling of soybeans (Glycine
max (L.) Merr.) is expressed as a reduction in individual plant yield components.
Any temporary suppression in plant growth due to herbicides may cause additional
yield reductions. Field studies were conducted to determine the response of
15 weed species and soybeans to acifluorfen, formesafen, and lactofen, and the
effect of these herbicides on foliar injury and seed yields of determinate soybeans
when seeded at post-optimal dates. Herbicides were applied to weeds and soybeans
at 3 wk after seeding and to soybeans in the V4 to V5 stage when grown under
weed-free conditions. Weed control was similar with all three herbicides. Differences
observed in weed control among herbicides appeared to be of little practical
importance. Soybeans exhibited differential herbicides tolerance (formesafen
> acifluorfen > lactofen ). Soybean injury increased as rates of acifluorfen
and lactofen increased, but was not affected by increasing rates of formesafen.
Soybean seed yields were not reduced by herbicides. Determinate soybeans seed
at post-optimal dates appear to recover from foliar injury caused by these herbicides
and seed yields are not affected.
Non-Human Toxicity Values:
LD50 Rat (male) oral 1250-2000 mg/kg
LD50 Rat (female) oral 1600 mg/kg
Ecotoxicity Values:
LD50 Mallard ducks oral >5000 mg/kg
LC50 Salmo gairdneri (rainbow trout) 680 mg/l/96 hr
LC50 Lepomis macrochirus (bluegill sunfish) 6030 mg/l/96 hr
Metabolism/Pharmacokinetics:
Absorption, Distribution & Excretion:
The use of organofluorine compounds has increased throughout this century,
and they are now ubiquitous environmental contaminants. Although generally viewed
as recalcitrant because of their lack of chemical reactivity, many fluorinated
organics are biologically active. Several questions surround their distribution,
fate, and effects. Of particular interest is the fate of perfluoroalkyl substituents,
such as the trifluoromethyl group. Most evidence to date suggest that such groups
resist defluorination, yet they can confer significant biological activity.
Certain volatile fluorinated compounds can be oxidized in the troposphere yielding
nonvolatile compounds, such as trifluoroacetic acid. In addition, certain nonvolatile
fluorinated compounds can be transformed in the biosphere to volatile compounds.
Research is needed to assess the fluorinated impurities present in commercial
formulations, and the transformation products generated by biochemical processes
and/or oxidation in the troposphere.
Mechanism of Action:
Using extracts from suspension-cultured cells of soybean (Glycine max cv.
Mandarin) as a source of active enzymes, the activities of glutathione transferases
(GSTs) catalyzing the conjugation of 1-chloro-2,4-dinitrobenzene (CDNB) and
selective herbicides were determined to be in the order 1-chloro-2,4-dinitrobenzene-ethyl.
glutathione transferase activities showed a thiol dependence in a substrate-specific
manner. Thus, glutathione transferase activities toward acifluorfen and formesafen
were greater when homoglutathione (hGSH), the endogenously occurring thiol in
soybean, was used as the co-substrate rather than glutathione (GSH). Compared
with glutathione, homoglutathione addition either reduced or had no effect on
glutathione transferase activities toward other substrates. In the absence of
enzyme, the rates of homoglutathione conjugation with acifluorfen, chlorimuron-ethyl
and formesafen were negligible, suggesting that rapid homoglutathione conjugation
in soybean must be catalyzed by glutathione transferases. glutathione transferase
activities were subsequently determined in 14-day-old plants of soybean and
a number of annual grass and broadleaf weeds. glutathione transferase activities
of the plants were then related to observed sensitivities to post-emergence
applications of the four herbicides. When enzyme activity was expressed on a
mg-1 protein basis, all grass weeds and Abutilon theophrasti contained considerably
higher glutathione transferase activity toward CDNB than soybean. With formesafen
as the substrate, glutathione transferase activities were determined to be in
the order soybean Digitaria sanguinalis > Sorghum halepense = Setaria faberi
with none of the broadleaf weeds showing any activity. This order related well
to the observed selectivity of formesafen, with the exception of A. theophrasti,
which was partially tolerant to the herbicide. Using metolachlor as the substrate
the order of the glutathione transferase activities was soybean > A. theophrasti
Amaranthus retroflexus > Ipomoea hederacea, with the remaining species showing
no activity. glutathione transferase activities toward metolachlor correlated
well with the selectivity of the herbicide toward the broadleaf weeds but not
toward the grass weeds. Acifluorfen and chlorimuron-ethyl were selectively active
on these species, but glutathione transferase activities toward these herbicides
could not be detected in crude extracts from whole plants.
Field studies were conducted in 1994 and 1995 to examine the effects of soybean
(Glycine max (L.) Merr.) row spacing and application rate and timing of four
postemergence herbicide tank mixtures on weed control and soybean yield. Weed
control and soybean yield were greater in narrow rows (7.5 in) than wide rows
(30 in). Herbicide tank mixtures applied at 25% of the full recommended rate
at an early postemergence timing followed by a second 25% application at a standard
postemergence timing (1/4x E Post + 1/4x Post) resulted in weed control and
soybean yield equal to that of herbicide tank mixtures applied at the full recommended
rate at a standard postemergence timing (1x Post). Three of four tank mixtures
in 1994 and two of four in 1995, applied at 50% of the full rate applied at
a standard postemergence timing (1/2x Post) resulted in weed control and soybean
yield equal to that of 1x Post applications. All tank mixtures applied at 50%
of the full rate at an early postemergence timing (1/2x E Post) resulted in
poor weed control and low soybean yield. In most cases it was more profitable
to plant soybean in narrow rows than wide rows regardless of application rate
or timing, based on economic gross margin calculations. Gross margins of tank
mixtures applied at 1/4x E Post + 1/4x Post were similar to or greater than
the gross margin of the same tank mixtures applied at the full rate in 13 of
16 cases. Gross margins of tank mixtures applied at 1/2x Post were similar to
or greater than the gross margin of the same tank mixture applied at the full
rate in eight of 16 cases.
Interactions:
Field studies were conducted in 1994 and 1995 in central and southern Illinois
to compare several total postemergence weed control programs in soybean (Glycine
max (L.) Merr.). Herbicide programs evaluated were imazethapyr (an acetolactate
synthase (ALS) inhibiting herbicide) applied alone or in combination with lactofen
and two non-acetolactate synthase herbicide programs consisting of combinations
of bentazon, acifluorfen, and sethoxydima and combinations of formesafen, fluazifop,
and fenoxyprop. These treatments were applied early postemergence (EPOST, V-1
soybean-first trifoliate) and postemergence (POST, V-2 soybean-second trifoliate).
Non-acetolactate synthase herbicide programs generally provide more effective
weed control postemergence, while weed control with imazethapyr tended to be
greater early postemergence. Non-acetolactate synthase herbicide programs applied
postemergence provided weed control levels that were equal to imazethapyr in
three out of four experiments. In 1994 at Brownstown, broadleaf weed control
was poor with non-acetolactate synthase herbicide programs when weed growth
stages were larger and environmental conditions more extreme than other experiments.
Adding lactofen to imazethapyr increased broadleaf weed control in some instances
but decreased giant foxtail (Setaria faberil L.) control. Imazethapyr plus lactofen
tended to produce the greatest degree of soybean injury.
Broadleaf weed and yellow nutsedge control with herbicide programs containing
pendimethalin and combinations of formesafen, fluometuron, and norflurazon applied
alone or with POST-directed applications of MSMA or fluometuron plus MSMA was
evaluated. Soil-applied herbicide combination containing formesafen controlled
yellow nutsedge better than combinations of norflurazon and fluometuron but
did not provide better entireleaf, ivyleaf, pitted, and tall morningglory or
sicklepod control. Fluometuron plus MSMA controlled morningglories and sicklepod
more effectively than MSMA. Seed cotton yield was greater in one of two years
when formesafen was applied and was associated with better yellow nutsedge control.
The objective of on-farm herbicide screening experiment sin soybean was to
assess the efficacy of new herbicides and herbicide combinations for weed control
in two tillage systems in Lusaka Province, Zambia weed control treatments consisted
of two control treatments (no-weeding and clean weeding with a hand hoe), two
standard treatments (metribuzin + metolachlor and formesafen + fluazifop-butyl)
and seven test herbicides/herbicide combinations (oxadiazon, oxadiazon + metolachlor,
imazethapyr, acifluorfen + fluazifop-butyl, bentazone + fluazifop-butyl, bentazone
+ fenoxaprop-ethyl and bentazone + acifluorfen). Loss of potential yield owing
to uncontrolled weeds was 66% and 40% under conventional and minimum tillage,
respectively. All herbicide treatments performed well wider conventional tillage,
whereas none of the treatments was able to satisfactorily control weeds under
minimum tillage, especially Euphorbia heterophylla and late weeds. Standard
herbicide treatments performed well under both tillage systems.
Field studies were conducted to determine rhizomatous johnsongrass and barnyardgrass
control with clethodim, quizalofop-P-ethyl, fluazifop-P, sethoxydim, fenoxaprop-ethyl,
and quizalofop-P-tefuryl applied alone and with lactofen, imazaquin, chlorimuron,
and formesafen. Graminicides applied alone controlled johnsongrass and barnyardgrass
83 to 99%. Of the graminicides evaluated, clethodium was the most antagonistic
of the broadleaf herbicides toward the activity of graminicides. Clethodim mixed
with imazaquin reduced johnsongrass control as much as 64% and mixed with chlorimuron
reduced barnyardgrass control as much as 52%. Quizalofop-P-tefuryl was least
affected by broadleaf herbicides and formesafen was least antagonistic in mixtures
with graminicides.
Field experiments were conducted to determine interactions of chlorimuron
or imazaquin with formesafen, lactofen, or acifluorfen on three-leaf and eight-leaf
common cocklebur, hemp sesbania, pitted morningglory, and prickly sida. Antagonism
was the most common interaction with common cocklebur, and was most severe with
chlorimuron combined with formesafen or acifluorfen, whereas lactofen did not
antagonize common cocklebur control. Reductions in control were greater when
ow rates of chlorimuron were used. On three-leaf prickly sida, control synergistically
increased when imazaquin was combined with formesafen or acifluorfen, but the
majority of these combinations were additive on eight-leaf prickly sida. Three-leaf
pitted morningglory control synergistically increased when 36 g ai/ha imazaquin
was combined with 210 g ai/ha formesafen or 110 or 220 g ai/ha lactofen. With
eight-leaf pitted morningglory, synergism occurred when 2 g ai/ha chlorimuron
was combined with the high rate of any diphenylether herbicide tested, and when
36 g/ha imazaquin was combined with 11- g/ha lactofen or 210 g ai/ha acifluorfen;
however, at higher rates of chlorimuron or imazequin, several antagonistic interactions
occurred. Hemp sesbania was controlled over 90% by all combinations, and no
interactions occurred.
Experiments were conducted to investigate the interactions of tank-mix combinations
of sethoxydim plus the sodium salt of bentazon, the sodium salt of acifluorfen,
formesafen, imazaquin, or the ethyl ester of chlorimuron. Antagonistic interactions
were observed with tank-mixes of sethoxydim plus bentazon, imazaquin, or chlorimuron
applied for fall pancium (Pancium dichotomiflorum), large crabgrass (Digitaria
sanguinalis) and goosegrass (Eleusine indica) control in field experiments.
Antagonism was observed in greenhouse experiments with tank-mixes of sethoxydim
plus bentazon or imazaquin applied to goosegrass. Bentazon, acifluorfen, and
formesafen reduced 14C-sethoxydim uptake by large crabgrass. However, imazaquin
and chlorimuron did not affect 14C-sethoxydim uptake. In field experiments,
no interactions occurred with tank-mixes of sethoxydim plus any of the broadleaf
weed control herbicides applied to entire leaf or tall morningglory (Ipomoea
hederacea var. Integriuscula and I. purpurea, respectively).
Pharmacology:
Interactions:
Field studies were conducted in 1994 and 1995 in central and southern Illinois
to compare several total postemergence weed control programs in soybean (Glycine
max (L.) Merr.). Herbicide programs evaluated were imazethapyr (an acetolactate
synthase (ALS) inhibiting herbicide) applied alone or in combination with lactofen
and two non-acetolactate synthase herbicide programs consisting of combinations
of bentazon, acifluorfen, and sethoxydima and combinations of formesafen, fluazifop,
and fenoxyprop. These treatments were applied early postemergence (EPOST, V-1
soybean-first trifoliate) and postemergence (POST, V-2 soybean-second trifoliate).
Non-acetolactate synthase herbicide programs generally provide more effective
weed control postemergence, while weed control with imazethapyr tended to be
greater early postemergence. Non-acetolactate synthase herbicide programs applied
postemergence provided weed control levels that were equal to imazethapyr in
three out of four experiments. In 1994 at Brownstown, broadleaf weed control
was poor with non-acetolactate synthase herbicide programs when weed growth
stages were larger and environmental conditions more extreme than other experiments.
Adding lactofen to imazethapyr increased broadleaf weed control in some instances
but decreased giant foxtail (Setaria faberil L.) control. Imazethapyr plus lactofen
tended to produce the greatest degree of soybean injury.
Broadleaf weed and yellow nutsedge control with herbicide programs containing
pendimethalin and combinations of formesafen, fluometuron, and norflurazon applied
alone or with POST-directed applications of MSMA or fluometuron plus MSMA was
evaluated. Soil-applied herbicide combination containing formesafen controlled
yellow nutsedge better than combinations of norflurazon and fluometuron but
did not provide better entireleaf, ivyleaf, pitted, and tall morningglory or
sicklepod control. Fluometuron plus MSMA controlled morningglories and sicklepod
more effectively than MSMA. Seed cotton yield was greater in one of two years
when formesafen was applied and was associated with better yellow nutsedge control.
The objective of on-farm herbicide screening experiment sin soybean was to
assess the efficacy of new herbicides and herbicide combinations for weed control
in two tillage systems in Lusaka Province, Zambia weed control treatments consisted
of two control treatments (no-weeding and clean weeding with a hand hoe), two
standard treatments (metribuzin + metolachlor and formesafen + fluazifop-butyl)
and seven test herbicides/herbicide combinations (oxadiazon, oxadiazon + metolachlor,
imazethapyr, acifluorfen + fluazifop-butyl, bentazone + fluazifop-butyl, bentazone
+ fenoxaprop-ethyl and bentazone + acifluorfen). Loss of potential yield owing
to uncontrolled weeds was 66% and 40% under conventional and minimum tillage,
respectively. All herbicide treatments performed well wider conventional tillage,
whereas none of the treatments was able to satisfactorily control weeds under
minimum tillage, especially Euphorbia heterophylla and late weeds. Standard
herbicide treatments performed well under both tillage systems.
Field studies were conducted to determine rhizomatous johnsongrass and barnyardgrass
control with clethodim, quizalofop-P-ethyl, fluazifop-P, sethoxydim, fenoxaprop-ethyl,
and quizalofop-P-tefuryl applied alone and with lactofen, imazaquin, chlorimuron,
and formesafen. Graminicides applied alone controlled johnsongrass and barnyardgrass
83 to 99%. Of the graminicides evaluated, clethodium was the most antagonistic
of the broadleaf herbicides toward the activity of graminicides. Clethodim mixed
with imazaquin reduced johnsongrass control as much as 64% and mixed with chlorimuron
reduced barnyardgrass control as much as 52%. Quizalofop-P-tefuryl was least
affected by broadleaf herbicides and formesafen was least antagonistic in mixtures
with graminicides.
Field experiments were conducted to determine interactions of chlorimuron
or imazaquin with formesafen, lactofen, or acifluorfen on three-leaf and eight-leaf
common cocklebur, hemp sesbania, pitted morningglory, and prickly sida. Antagonism
was the most common interaction with common cocklebur, and was most severe with
chlorimuron combined with formesafen or acifluorfen, whereas lactofen did not
antagonize common cocklebur control. Reductions in control were greater when
ow rates of chlorimuron were used. On three-leaf prickly sida, control synergistically
increased when imazaquin was combined with formesafen or acifluorfen, but the
majority of these combinations were additive on eight-leaf prickly sida. Three-leaf
pitted morningglory control synergistically increased when 36 g ai/ha imazaquin
was combined with 210 g ai/ha formesafen or 110 or 220 g ai/ha lactofen. With
eight-leaf pitted morningglory, synergism occurred when 2 g ai/ha chlorimuron
was combined with the high rate of any diphenylether herbicide tested, and when
36 g/ha imazaquin was combined with 11- g/ha lactofen or 210 g ai/ha acifluorfen;
however, at higher rates of chlorimuron or imazequin, several antagonistic interactions
occurred. Hemp sesbania was controlled over 90% by all combinations, and no
interactions occurred.
Experiments were conducted to investigate the interactions of tank-mix combinations
of sethoxydim plus the sodium salt of bentazon, the sodium salt of acifluorfen,
formesafen, imazaquin, or the ethyl ester of chlorimuron. Antagonistic interactions
were observed with tank-mixes of sethoxydim plus bentazon, imazaquin, or chlorimuron
applied for fall pancium (Pancium dichotomiflorum), large crabgrass (Digitaria
sanguinalis) and goosegrass (Eleusine indica) control in field experiments.
Antagonism was observed in greenhouse experiments with tank-mixes of sethoxydim
plus bentazon or imazaquin applied to goosegrass. Bentazon, acifluorfen, and
formesafen reduced 14C-sethoxydim uptake by large crabgrass. However, imazaquin
and chlorimuron did not affect 14C-sethoxydim uptake. In field experiments,
no interactions occurred with tank-mixes of sethoxydim plus any of the broadleaf
weed control herbicides applied to entire leaf or tall morningglory (Ipomoea
hederacea var. Integriuscula and I. purpurea, respectively).
Environmental Fate & Exposure:
Environmental Fate/Exposure Summary:
Fomesafen's production and use as a contact broadleaf herbicide is expected
to result in its direct release to the environment. If released to air, a vapor
pressure of <7.5X10-7 mm Hg at 50 deg C indicates that fomesafen will exist
in both the vapor and particulate phases in the ambient atmosphere. Vapor-phase
fomesafen will be degraded in the atmosphere by reaction with photochemically-produced
hydroxyl radicals; the half-life for this reaction in air is estimated to be
10 days. Particulate- phase fomesafen may be removed from the atmosphere by
wet and dry deposition. Fomesafen will photodecompose readily under relatively
low intensities of sunlight. If released to soil, measured Koc values ranging
from 150 to 1200 indicate fomesafen is expected to have low to high mobility.
Fomesafen is not expected to volatilize from wet or dry soil surfaces based
on an estimated Henry's Law constant of 7.5X10-13 atm-cu m/mole and this compound's
vapor pressure, respectively. Biodegradation of fomesafen in soil is expected
to be an important fate process under anaerobic conditions, with a half-life
of generally less than 3 weeks. If released into water, some adsorption of fomesafen
to suspended solids and sediment in the water column is expected based upon
the measured Koc values. A pKa of 2.7 indicates fomesafen will exist almost
entirely in the ionized form at pH values of 5 to 9 and therefore volatilization
from water surfaces is not expected to be an important fate process. An estimated
BCF of 17 suggests the potential for bioconcentration in aquatic organisms is
low. Occupational exposure to fomesafen may occur through inhalation of spray
mists and aerosols and dermal contact with this herbicide during or after its
application or at workplaces where fomesafen is produced. (SRC)
Probable Routes of Human Exposure:
Occupational exposure to fomesafen may occur through inhalation of spray mists
and aerosols and dermal contact with this herbicide during or after its application
or at workplaces where fomesafen is produced. (SRC)
Artificial Pollution Sources:
Fomesafen's production and use as a contact broadleaf herbicide(1) is expected
to result in its direct release to the environment(SRC).
Environmental Fate:
TERRESTRIAL FATE: Based on a classification scheme(1), soil Koc values ranging
from 150 to 1200(2), indicate that fomesafen is expected to have low to high
mobility in soil(SRC). Volatilization of fomesafen from moist soil surfaces
is not expected to be important(SRC) given an estimated Henry's Law constant
of 7.5X10-13 atm-cu m/mole(SRC), using a fragment constant estimation method(4).
Fomesafen is not expected to volatilize from dry soil surfaces based on a vapor
pressure of <7.5X10-7 mm Hg(5). Biodegradation of fomesafen is expected to
be an important fate process in soil(SRC): a half- life of less than 3 weeks
is expected under anaerobic conditions; under aerobic conditions, half-lives
range from about 6 months to greater than 12 months depending on soil type(6).
AQUATIC FATE: Based on a classification scheme(1), soil Koc values ranging
from 150 to 1200(2), indicate that some adsorption of fomesafen to suspended
solids and sediment in water is expected(SRC). Fomesafen's pKa of 2.7(6) indicates
that this compound will exist almost entirely in the ionized form at pH values
of 5 to 9 and therefore volatilization from water surfaces is not expected to
be an important fate process(SRC). According to a classification scheme(5),
an estimated BCF of 17(3,SRC), from a water solubility of >600 mg/l at pH
7(6), suggests that bioconcentration in aquatic organisms is low(SRC). Biodegradation
of fomesafen in aquatic systems may be important(SRC) based upon its biodegradation
in soil under anaerobic conditions(7). Fomesafen will photodecompose readily
under relatively low intensities of sunlight(7).
ATMOSPHERIC FATE: According to a model of gas/particle partitioning of semivolatile
organic compounds in the atmosphere(1), fomesafen, which has a vapor pressure
of <7.5X10-7 mm Hg at 50 deg C(2), will exist in both the vapor and particulate
phases in the ambient atmosphere. Vapor-phase fomesafen is degraded in the atmosphere
by reaction with photochemically-produced hydroxyl radicals(SRC); the half-life
for this reaction in air is estimated to be about 10 days(3,SRC). Particulate-phase
fomesafen may be physically removed from the air by wet and dry deposition(SRC).
Fomesafen will photodecompose readily under relatively low intensities of sunlight(4).
Environmental Biodegradation:
In soil, fomesafen is rapidly decomposed under anaerobic conditions, with
a half-life of less than 3 weeks(1). In laboratory soil studies under aerobic
conditions, half-lives range from about 6 months to greater than 12 months depending
on soil type(1).
Environmental Abiotic Degradation:
The rate constant for the vapor-phase reaction of fomesafen with photochemically-produced
hydroxyl radicals has been estimated as 1.6X10-12 cu cm/molecule-sec at 25 deg
C(SRC) using a structure estimation method(1,SRC). This corresponds to an atmospheric
half-life of about 10 days at an atmospheric concentration of 5X10+5 hydroxyl
radicals per cu cm(1,SRC). Fomesafen will photodecompose readily under relatively
low intensities of sunlight(2). The UV absorption spectrum of fomesafen in aqueous
solution consists of a single smooth peak at 300 nm(3) indicating fomesafen
may be susceptible to direct photolysis(SRC).
Environmental Bioconcentration:
An estimated BCF of 17 was calculated for fomesafen(SRC), using a water solubility
of >600 mg/l at pH 7(1) and a regression-derived equation(2). According to
a classification scheme(3), this BCF suggests that bioconcentration in aquatic
organisms is low.
Soil Adsorption/Mobility:
Kom values of 86 and 700 were determined for fomesafen in Drummer silt loam
and Norfolk sandy loam, respectively(1). These values correspond to Koc values
of 150 and 1200, respectively(2,SRC). According to a classification scheme(3),
these measured Koc values suggest that fomesafen is expected to have low to
high mobility in soil(SRC). Sorption of fomesafen by both soils increased greatly
as pH decreased: on the Drummer soil it increased from 14% at pH 6.3 to 42 and
95% at pH 4.7 and 2.0, respectively; on the Norfolk soil, fomesafen sorption
increased from 5% at pH 5.3 to 15 and 55% at pH 4.0 and 2,0, respectively(1).
4% of fomesafen was sorbed by Ca-montmorillonite(1). In laboratory soil studies,
fomesafen's mobility was similar to that of atrazine, moderately mobile(4).
Volatilization from Water/Soil:
The Henry's Law constant for fomesafen is estimated as 7.5X10-13 atm-cu m/mole(SRC)
using a fragment constant estimation method(1). This Henry's Law constant indicates
that fomesafen is expected to be essentially nonvolatile from water surfaces(2,SRC).
A pKa of 2.7 for fomesafen(3) also indicates that it will not significantly
volatilize from water or soil surfaces as it will exist predominately in the
ionized form under environmental pHs(SRC).
Environmental Standards & Regulations:
FIFRA Requirements:
Tolerances are established for the residues of sodium salt of fomesafen, 5-(2-chloro-4-(trifluoromethyl)phenoxy)-N-(methylsulfonyl)-2-nitrobenzamide,
in or on soybeans.
Allowable Tolerances:
Tolerances are established for the residues of sodium salt of fomesafen, 5-(2-chloro-4-(trifluoromethyl)phenoxy)-N-(methylsulfonyl)-2-nitrobenzamide,
in or on soybeans at 0.05 ppm.
Chemical/Physical Properties:
Molecular Formula:
C15-H10-Cl-F3-N2-O6-S
Molecular Weight:
438.8
Color/Form:
Colorless crystals.
White crystalline solid.
Melting Point:
220 to 221 deg C
Corrosivity:
Noncorrosive under normal use conditions.
Density/Specific Gravity:
1.28 g/ml at 20 deg C
Dissociation Constants:
pKa approx. 2.7 at 20 deg C
Octanol/Water Partition Coefficient:
log Kow = 2.9 at pH 1
Solubilities:
Soluble in water 50 mg/l at 25 deg C and pH 7; less than 1 mg/l at pH 1.
Soluble in a range of organic solvents. /Technical material/
Vapor Pressure:
<7.5X10-7 mm Hg at 50 deg C
Other Chemical/Physical Properties:
Stable in storage for at least 6 months at 50 deg C. Decomposed by light.
Resistant to hydrolysis under both acidic and alkaline conditions. Forms water-soluble
salts.
Chemical Safety & Handling:
Skin, Eye and Respiratory Irritations:
Mild skin irritant; mild to moderate eye irritant (rabbits).
Hazardous Decomposition:
Decomposed by light.
Preventive Measures:
SRP: The scientific literature for the use of contact lenses in industry is
conflicting. The benefit or detrimental effects of wearing contact lenses depend
not only upon the substance, but also on factors including the form of the substance,
characteristics and duration of the exposure, the uses of other eye protection
equipment, and the hygiene of the lenses. However, there may be individual substances
whose irritating or corrosive properties are such that the wearing of contact
lenses would be harmful to the eye. In those specific cases, contact lenses
should not be worn. In any event, the usual eye protection equipment should
be worn even when contact lenses are in place.
Stability/Shelf Life:
Stable in storage for at least 6 months at 50 degrees C
Storage Conditions:
Stable in storage for at least 6 months at 50 deg C. Decomposed by light.
Resistant to hydrolysis under both acidic and alkaline conditions. Forms water-soluble
salts.
Disposal Methods:
SRP: At the time of review, criteria for land treatment or burial (sanitary
landfill) disposal practices are subject to significant revision. Prior to implementing
land disposal of waste residue (including waste sludge), consult with environmental
regulatory agencies for guidance on acceptable disposal practices.
Occupational Exposure Standards:
Manufacturing/Use Information:
Major Uses:
Herbicide. Selective annual broadleaf weed killer and has activity on some
grass and sedge species.
Contact broadleaf herbicide. Postemergence, over the top, on soybeans.
Fomesafen was used on crops during the 1990 to 1993 crop years.
Field experiments were conducted from 1991 to 1993 to evaluate eclipta, Eclipta
prostrate L., control and peanut, Arachis hypogaea L., response to herbicide
treatments. Formesafen (5-(2-chloro-4-(trifluoromethyl)phenoxy)-N-(methylsulfonyl)-2-nitrobenzamide)
applied at cracking was the only preemergence-applied herbicide which provided
season-long control (>84%). Herbicides applied postemergence were more effective
when the eclipta was less than 5 cm in height. The most consistent early postemergence
treatments were bromoxynil (3,5-dibromo-4-hydroxybenzonitrile), bentazone (3-(1-methylethyl)-(1H)-2,1,3-benzothiadiazin-4(3H)-one-2,2-dioxide),
and bentazon + acifluorfen (5-2-chloro-4-(trifluoromethyl)phenoxy)-2-nitrobenzoic
acid) + 2,4-DB (4-(2,4-dichloro-phenoxy)butanoic acid). Various other early
postemergence followed by late postemergence sequential treatments also were
equally effective. Minor peanut injury was observed at the early season rating
from several herbicides; however, all injury had disappeared by the late season
rating. Eclipta control did not consistently improve peanut pod yield.
Methods of Manufacturing:
Acifluorfen + ammonia + methanesulfonyl chloride (amide formation/sulfonamide
formation).
General Manufacturing Information:
Fomesafen was used on the following crops during the 1990 to 1993 crop years
(from federal and state pesticide use surveys), by crop (State, % of crop acreage
treated based on estimates of the crop's 1992 planted acreage): green beans
(AR, 70%; IL, 50%) and soybeans (AL, 10%; AR, 13%; FL, 2%; GA, 2%; IL, 2%; IN,
2%; KY, 16%; LA, 15%; MI, 3%; MS, 10%; MO, 2%; NC, 6%; OH, 3%; SC, 6%; and TN,
9%).
Formulations/Preparations:
Aqueous concentration, liquid concentration.
Soluble concentrate.
Consumption Patterns:
In 1989, the national usage of formesafen was 227,000 lbs AI/year in U.S.
agriculture.
Laboratory Methods:
Analytic Laboratory Methods:
Product analysis by HPLC with UV detection. Residue analysis in soil by HPLC;
in crops by TLC, HPLC or NMR. Details available from Zeneca.
Special References:
Special Reports:
Retzinger E J Jr and C Mallory-Smith; Weed Technology 11 (2): 384-393 1997.
Classification of herbicides by site of action for weed resistance management
strategies.
Tsuda T et al; Journal of Pesticide Science 22 (3): 218-221 1997. Synthesis
of N-alkyl-2,3-dimethyl-5-N'-5-halo-2-methylphenylcarbamoyl-6-pyrazinecarboxamides
and their herbicidal activity.
Chamberlain K et al; Pesticide Science 47 (3): 265-271 1996. 1-Octanol/water
partitition coefficient (Kow) and pKa for ionizable pesticides measured by a
pH-metric method.
Elcombe CR et al; Ann NY Acad Sci 804: 628-35 1996. Peroxisome proliferators:
species differences in response of primary hepatocyte cultures.
Georgiev G TS; Dokladi Na B"Lgarskata Akademiya Na Naukite 49 (3): 83-86 1996.
Effect of combined application of certain herbicides and phenylurea cytokinin
4-Pu-30 on soybean growth and productivity.
Knott CM; Annals of Applied Biology 128 (Suppl.): 38-39 1996. Evaluation of
herbicides for weed control in runner beans phaseolus coccineus.
Knott CM; Annals of Applied Biology 128 (Suppl.): 54-55 1996. Tolerance of
spring-sown lupins lupinus albus to herbicides.
Shad RA and SU Siddiqui; Experimental Agriculture 32 (2): 151-160 1996. Problems
associated with Phalaris minor and other grass weeds in India and Pakistan.
South DB and JB Zwolinski; Southern Journal of Applied Forestry 20 (3): 127-135
1996. Chemicals used in southern forest nurseries.
Talbert NE et al; Arkansas Agricultural Experiment Station Research Series
0 (452): I-IV, 1-38 1996. Field evaluations of herbicides on small fruit vegetable
and ornamental crops 1995.
Mahmoud S MM et al; Egyptian Journal of Phytopathology 22 (1): 39-57 1994.
Some aspects affecting preplanting management of cotton seedling disease caused
by Rhizoctonia solani.
Mayer AS et al; Water Environment Research 66 (4): 532-585 1994. Fate and
effects of pollutants groundwater quality.
Mineau P et al; Ecotoxicology and Environmental Safety 29 (3): 304-329 1994.
An analysis of avian reproduction studies submitted for pesticide registration.
Orfila L and M Salazar-Bookaman; Rev Fac Farm Univ Cent Venez 57 (1): 6-11
1994. Cytotoxic activity of the herbicide formesafen in rat hepatocytes treated
in vitro.
Eyherabide JJ; Tests Agrochem Cultiv 0 (13): 56-57 1992. Evaluation of pre-emergence
applications of formesafen and acetochlor against weeds in soybeans.
Zanin G et al; Crop Prot 11 (2): 174-180 1992. Economics of herbicide use
on arable crops in north-central Italy.
Lalova M and L Tyankova; C R Acad Bulg Sci 44 (9): 89-91 1991. Influence of
herbicides on soybean fatty acids.
Beal DD; Progress in Clinical and Biological Research 331: 5-18 1990. Use
of mouse liver tumor data in risk assessments performed by the USA EPA.
Rana MA et al; Crop Res 3 (1): 40-50 1990. Effect of maturity stages and desiccant
application on seed yield and oil quality of sunflower (Helianthus annuus L.).
Rovesti L and KV Deseo; Nematologica 36 (2): 237-245 1990. Compatibility of chemical pesticides with the entomopathogenic nematodes: Steinernema carpocapsae Weiser and Steinernema feltiae Filipjev (Nematoda: Steinernematidae).
Synonyms and Identifiers:
Synonyms:
5-[2-chloro-4-(trifluoromethyl)phenoxy]-N-(methylsulfonyl)-2-nitrobenzamide
**PEER REVIEWED**
5(2-chloro-alpha,alpha,alpha-trifluoro-p-tolyloxy)-N-mesyl-2-nitrobenzamide
**PEER REVIEWED**
5(2-chloro-alpha,alpha,alpha-trifluoro-p-tolyloxy)-N-methylsulfonyl-2-nitrobenza
mide
**PEER REVIEWED**
Formulations/Preparations:
Aqueous concentration, liquid concentration.
Soluble concentrate.
Administrative Information:
Hazardous Substances Databank Number: 6660
Last Revision Date: 20000929
Last Review Date: Reviewed by SRP on 5/7/1998
Update History:
Complete Update on 09/11/1998, 49 fields added/edited/deleted.