fluridone (Sonar, Brake, Pride) Herbicide Profile 3/86
CHEMICAL FACT SHEET FOR
FACT SHEET NUMBER: 81
DATE ISSUED: MARCH 31, 1986
Description of Chemical
- Generic Name: 1-methyl-3-phenyl-5-3-(trifluoromethyl)phenyl|-
- Common Name: fluridone
- Trade Name: Sonar
- EPA Shaughnessy Code: 112900
- Chemical Abstracts Service (CAS) Number: 59756-60-4
- Year of Initial Registration: 1986
- Pesticide Type: Aquatic herbicide
- Status: General use
- U.S. and Foreign Producers:
Elanco Products Co.
Div. of Eli Lilly and Co.
740 South Alabama St.
Indianapolis, IN 46285
Summary of Regulatory Position and Rationale (Source: NPIRS):
- Risk/benefit review: None of the risk criteria set forth in Title
40 Code of Federal Regulations Section 162.11 have been exceeded
- Fluridone has been proposed only for direct application to aquatic
sites. No groundwater contamination issue is associated with this
Use Patterns and Formulations (Source: NPIRS):
- Application sites: Freshwater ponds, lakes, reservoirs, drainage
canals, irrigation canals, and rivers.
- Types of formulations: Aqueous suspension, pellet
- Types and methods of application: Surface spray, weighted hose
dragged near bottom; broadcast (pellet)
- Application rates: 0.5 lb. a.i./surface acre - 4.0 lb. a.i./
- Usual carrier: water
Fluridone controls most submerged and emerged aquatic plants.
Some of the weeds controlled by fluridone include fanwort (Cabomba
caroliniana), coontail (Ceratophyllum demersum), elodea (Elodea
canadensis), parrot feather (Myriophyllum brasiliense), watermilfoil
(Myriophyllum spp.) naiad (Najas quadalupensis), pickerelweed
(Pontederia lanceolata), pondweed (Potamogeton spp.), arrowhead
(Sagittaria spp), bladderwort (Utricularia spp.), Vallisneria
(Vallisneria spp.), hydrilla (Hydrilla verticillata) and certain
shoreline grasses such as maidencane (Panicum hemitomon), paragrass
(Panicum purpurascens), torpedograss (Panicum repens), and reed
canarygrass (Phalarsis arundinacea). Fluridone has little effect on
algae and provides only partial control of the cattails (Typha spp.).
In addition, most floating aquatic weeds are only partially affected by
fluridone applications (58).
Important Weeds Controlled: Aquatic weeds, barnyardgrass, Bermudagrass,
blackgrass, cocklebur, crabgrass, foxtails, jimsonweed, Johnsongrass,
lambsquarters, morningglory, nightshade, nutsedge, pigweed, purslane,
ragweed, velvetleaf and many others (8b).
As little as 0.1 inch of rainfall will activate the material. A
long residual activity, so further investigation is needed to determine
what crops can be planted the following season after treatment. Weeds
may germinate and emerge from the soil before they get a chlorotic
condition and then die. A very broad spectrum herbicide. Effective at
extremely low rates. In aquatics, little or no weed control is noted
for 2-4 weeks (8b).
II. PHYSICAL PROPERTIES
- Chemical Characteristics
Fluridone is a white (to off-white) crystalline solid with no odor.
The melting point is 154-155 C. The flash point for the aqueous
suspension formulation is greater than 200 degrees. Fluridone is
not corrosive to application equipment (NPIRS).
Molecular Formula: C19 H14 F3 NO (62)
Molecular Weight: 329.3 (62)
Physical State: Off-white crystalline solid (pure compound) (62)
Melting Point: 151-154 C (pure compound) (62)
Vapor Pressure: 13 uPa at 25 C (pure compound) (62)
Solubility: 0.0012 g/100 ml water (pure compound) (58)
III. SCIENTIFIC INFORMATION
Osha Standard: NA
NIOSH Recommended Limit: NA
ACGIH Recommended Limit: NA
A. Toxicology Characteristics (Sources other than NPIRS):
1. Acute toxicity:
Fluridone was administered to rats and mice as a single dose given
either orally or subcutaneously. Dogs and cats received a single oral
dose administered in capsules. The acute toxicity of an aqueous
suspension formulation containing 45 percent fluridone was evaluated by
administering a single application of the material to the skin or eyes
of rabbits. Inhalation was evaluated in rats exposed for 1 hr to an
atmosphere containing the compound or formulation. The toxic effects
of these treatments are summarized below (58).
DERMAL: LD50 = >2,000 g/kg (rat, technical); >500 mg/kg
(rabbit, technical; no irritation); >2 ml/kg
(rabbit, 2 AS; slight irritant) (58).
LD50 = >2,000 mg/kg (mouse, technical) (58).
ORAL: LD50 = >10,000 mg/kg (rat, technical); >10,000
mg/kg (mouse, technical) (58).
LD50 = >0.5 ml/kg (rat, 4 AS); >250 mg/kg (cat,
technical); >500 mg/kg (dog, technical) (58).
INHALATION: LC0 = >2,130 mg/m3 of air (rat, technical); >9.6
ml/m3 of air (rat, 4AS) (58).
EYES: Moderate irritant (rabbit, 44 mg/eye, technical);
very slight irritant (rabbit, 0.1 ml/eye, 4 AS) (58).
2. Subacute and chronic toxicity:
Fluridone has been evaluated for a period of three months in rats,
mice and dogs. An increase in liver and kidney weights as well as the
histological identification of liver centrilobular hypertrophy occurred
in rats fed diets containing 1,400 pm of fluridone. Liver
centrilobular hypertrophy was also observed in mice receiving diets
containing 560 ppm of fluridone. No treatment-related effects were
noted in rats at dietary doses of 330 ppm or noted in mice at dietary
doses of 62 ppm. No toxic effects were observed in dogs receiving up
to 200 mg/kg/day of fluridone (58).
B. Toxicology Characteristics (Source: NPIRS):
- Acute toxicology: Technical fluridone is in Category IV for acute
oral effects in the rat, and is moderately toxic through acute
inhalation exposure. Eye irritation potential has been demon-
strated as moderate to severe (Category III and Category II). The
aqueous suspension and pellet formulations are in Category III for
oral, dermal, skin, and eye irritation effects.
- Chronic toxicology: A complete, acceptable chronic toxicity data
base is available, except for a rat teratology study (second
species). A valid rabbit teratology study indicates no terato-
genic response up to a dose level of 300 mg/kg/day. Fluridone is
not considered to have produced an oncogenic response in the mouse
or rat. Mutagenicity assays submitted do not indicate genotoxic
potential, gene mutation, or structural chromosomal aberration.
C. Physiological and Biochemical Behavioral Characteristics (Source: NPIRS):
Fluridone is a systemic herbicide; it is absorbed from water by
plant shoots and from hydrosoil by roots. It inhibits carotenoid
synthesis, which enhances degradation of chlorophyll, producing
white (chlorotic) growing points in susceptible plants.
D. Tolerance Assessment (Source: NPIRS):
- A tolerance is proposed for residues of the herbicide fluridone
pyridinone) and its metabolite (1-methyl-3-(4-hydroxyphenyl)-5-
3-(trifluoromethyl)phenyl|-4(1H)-pyridinone) in fish at 0.5 ppm.
- Tolerances are proposed for residues of the herbicide fluridone
in the following raw agricultural commodities:
Commodity Parts per million
Cattle, fat 0.05
Cattle, kidney 0.1
Cattle, liver 0.1
Cattle, meat byproducts 0.05
Cattle, meat (except liver and kidney) 0.05
Goats, fat 0.05
Goats, kidney 0.1
Goats, liver 0.1
Goats, meat byproducts 0.05
Goats, meat (except liver and kidney) 0.05
Hogs, fat 0.05
Hogs, kidney 0.1
Hogs, liver 0.1
Hogs, meat byproducts 0.05
Hogs, meat (except liver and kidney) 0.05
Horses, fat 0.05
Horses, kidney 0.1
Horses, liver 0.1
Horses, meat byproducts 0.05
Horses, meat (except liver and kidney) 0.05
Poultry, fat 0.05
Poultry, kidney 0.1
Poultry, liver 0.1
Poultry, meat byproducts 0.05
Poultry, meat (except liver and kidney) 0.05
Sheep, fat 0.05
Sheep, kidney 0.1
Sheep, liver 0.1
Sheep, meat byproducts 0.05
Sheep, meat (except liver and kidney) 0.05
- Tolerances are proposed in the following irrigated crops and crop
groupings for residues of the herbicide fluridone resulting from
use of irrigation water containing residues of 0.15 ppm following
applications on or around aquatic sites. Where tolerances are
established at higher levels from other uses of fluridone on the
following crops, the higher tolerance also applies to residues
in the irrigated commodity. The tolerances follow:
Commodity Parts per million
Forage grasses 0.15
Forage legumes 0.15
Fruiting vegetables 0.1
Grain crop 0.1
Leafy vegetables 0.1
Pome fruit 0.1
Root crops - vegetables 0.1
Seed and pod vegetables 0.1
Small fruit 0.1
Stone fruit 0.1
- Based on the NOEL of 8 mg/kg/day in the chronic rat feeding study
and a 100-fold safety factor, the Acceptable Daily Intake (ADI)
has been set at 0.08 mg/kg/day, with a Maximum Permissible Intake
(MPI) of 4.8 mg/day for a 60-kg person. There are no previously
established tolerances for this herbicide.
- The Agency is designating an acceptable residue level for
fluridone in potable water at 0.15 ppm. This concentration
reflects the maximum application rate for the herbicide regis-
tration(s) issued pursuant to FIFRA. Consumption of water is
estimated at 2.0 liters per day for a 60-kg adult. These
tolerances and the acceptable residue level in potable water
result in a Theoretical Maximum Residue Contribution of 0.4112
mg/day in a 1.5-kg diet (including 2 liters of water), and use
8.57% of the ADI.
- No Mexican, Canadian, or Codex maximum residue levels have been
established. Residue studies are adequate to support the
proposed tolerances. Plant and animal metabolism is adequately
understood, and adequate analytical methods are available to
enforce the tolerance levels. The residue of concern in drinking
water is parent compound, i.e. fluridone.
E. Summary Science Statement (Source: NPIRS)
Supporting data base for fluridone registration and tolerance
proposals supporting aquatic use is complete and acceptable, except
for a second species (rat) teratogenic study. Original study
submitted did not produce teratogenic response at any level tested.
The study, however, is not adequate for regulatory purposes, because
the highest dose tested did not produce frank maternal toxicity or
fetotoxicity. The study is presently being repeated.
F. Summary of Major Data Gaps (Source: NPIRS)
An additional rat (second species) teratology study is underway.
Schedule for submission is July 1, 1986.
G. Contact Person at EPA:
Richard F. Mountfort
Product Manager 23
Environmental Protection Agency
401 M Street S.W.
Washington, DC 20460
IV. ENVIRONMENTAL/ECOLOGICAL CONSIDERATIONS
A. Environmental Characteristics (Source: NPIRS):
- Degradation: Fluridone is stable to hydrolysis. It will photo-
degrade (half-life is 34 hours in neutral pond water).
- Persistence: Under anaerobic aquatic conditions, fluridone has a
half-life of nine months. The half-life for fluridone in water
is estimated to be 20 days; for hydrosoil, 90 days.
1. Behavior In or On soils (58):
a. Adsorption and leaching characteristics in basic soil types:
Fluridone is strongly adsorbed to organic matter in soil.
Regression analysis suggests that organic matter can be used to
predict the rate of fluridone required for herbicidal activity.
There is also good correlation between adsorption/desorption
coefficients and the organic matter content of the soil. Column
leaching studies indicate that fluridone leaches slowly in the
b. Microbial breakdown: Microorganisms appear to be the major factor
responsible for the degradation of fluridone in terrestrial
c. Loss from photodecomposition: In an aquatic environment fluridone
appears to be degraded principally by photolytic processes;
however, microorganisms and aquatic vegetation may also be
factors in the dissipation process.
d. Resultant average persistence at recommended rates: The per-
sistence of fluridone in terrestrial soils is complex and
not well defined. In most cotton producing areas, residues may
carry over to the next cropping season and may cause injury to
crops such as corn, sorghum, soybeans, sugar beets, and tomatoes
that follow in rotation. There appears to be little relation-
ship between the rainfall pattern, soil texture and land tillage
to soil persistence of fluridone. When used for the control of
aquatic vegetation, fluridone exhibits a half-life in water of
approximately 21 days.
B. Ecological Characteristics (Source: NPIRS):
1. Avian studies:
- Acute oral (bobwhite quail), >2,000 mg/kg
(slightly toxic). Avian dietary (bobwhite quail and mallard duck),
>5,000 ppm. No impairment on reproduction for above species up
to 1,000 ppm dietary exposure.
2. Aquatic species studies:
- Daphnia magna 48-hour acute is 6.3 mg/L (moderately toxic).
- Bluegill sunfish 96-hour acute is 12 mg/L (moderately toxic).
- Rainbow trout 96-hour acute is 11.7 mg/L (moderately toxic).
- Sheepshead minnow 96-hour acute is 10.91 mg/L (moderately toxic).
- Oyster embryo-larvae 48-hour acute is 16.51 mg/L (moderately
- Maximum Acceptable Theoretical Concentration (MATC) value for
fathead minnow (second generation fry) was calculated to be
>0.48 <0.96 mg/L. No treatment-related effects were observed
at or below 0.48 mg/L. Total length of 3-day-old fry was
reduced at 2 mg/L fluridone.
3. Potential problems for endangered species:
- Acute and MATC values indicate a potential hazard for aquatic
organisms in shallow areas at higher treatment rates described on
the label. Formal consultation with Office of Endangered Species
(OES) has been initiated. To minimize hazard, label directions
provide for use of lowest listed rates for shallow areas, and
consultation with Fish and Game Agency or U.S. Fish and Wildlife
Service if questions arise concerning aquatic resources in the area
to be treated.
4. General Toxicity to Wildlife and Fish (58):
- Fluridone was administered to one-week old mallard and bobwhite as a
component of the diet for four days or to adult bobwhite as a single
dose. Bluegills and rainbow trout were exposed to the compound for
96 hr in static toxicity tests. Similar static tests were
coneducted with Daphnia magna for a duration of 48 hr. The LD50 and
LC50 values determined by these tests are summarized as follow:
Species Route Toxicity
_______ _____ ________
Mallard Diet (4 days) LC50 >5,000 ppm
Bobwhite Diet (4 days) LC50 >5,000 ppm
Bobwhite Oral (acute) LD50 >5,000 mg/kg
Bluegill Water (static) LC50 >9<12.5 ppm
Rainbow Water (static) LC50 = 11.7 ppm
Daphnia (Daphnia magna) Water (static) LC50 = 6.3 ppm
V. EMERGENCY AND FIRST AID PROCEDURES
The chemical information provided below has been condensed from
original source documents, primarily from "Recognition and Management
of Pesticide Poisonings", 3rd ed. by Donald P. Morgan, which have been
footnoted. This information has been provided in this form for your
convenience and general guidance only. In specific cases, further
consultation and reference may be required and is recommended. This
information is not intended as a substitute for a more exhaustive
review of the literature nor for the judgement of a physician or other
If poisoning is suspected, do not wait for symptoms to develop.
Contact a physician, the nearest hospital, or the nearest Poison
SYMPTOMS OF POISONING: No cases of poisoning have been reported or
SKIN CONTACT: Wash affected areas with soap and water (58).
EYE CONTACT: Flush eyes with large quantities of water (58).
VI. FIRE AND EXPLOSION INFORMATION
None of the formulations are flammable (58).
Incompatibility with water of any hardness has not been
experienced. Fluridone has been successfully tank-mixed with many
other herbicides. None of the formulations have demonstrated
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Keep out of reach of children. Avoid freezing.
Store above 32 F. Harmful if swallowed, inhaled, or absorbed through
skin. Avoid breathing vapors or spray mist. Avoid contact with skin,
eyes, or clothing (56).
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
X. LITERATURE CITED
8b. Thomson, W.T. 1981. Agricultural chemicals - book 2:
herbicides. Revised ed. Thomson Publications, Fresno, CA.
56. Farm Chemicals Handbook, 70th ed. 1984. R. T. Meister, G. L.
Berg, C. Sine, S. Meister, and J. Poplyk, eds. Meister
Publishing Co., Willoughby, OH.
58. Weed Science Society of America, Herbicide Handbook Committee.
1983. Herbicide handbook of the weed science society of
America, 5th ed. Weed Science Society of America, Champaign,
IL. 515 pp.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.