bensulide (Betasan, Prefar) Herbicide Profile 3/85
CHEMICAL NAME: [S-(O,O-diisopropyl phosphorodithioate)ester of
TRADE NAME(S): Betasan, Betamec, Exporsan, Prefar, Pre-San (56)
FORMULATION(S): Emulsifiable concentrate (4 lb/gal), granules
(12.5%, 7%, 3.6%) (56).
BASIC PRODUCER(S): PBI-Gordon Corp. Stauffer Chemical Co.
P.O. Box 4090 Agricultural Chem. Div.
Kansas City, MO 64101 Westport, CT 06881
STATUS: General use
PRINCIPAL USES: Betasan is registered for control of crabgrass,
annual bluegrass, redroot pigweed, watergrass, lambsquarters,
shepherdspurse, goosegrass, and deadnettle in grass and dichondra lawns.
Prefar is registered for controlling various grass and broadleaf weeds in
cotton, lettuce, cucumbers, cantaloupes, squash (summer and winter),
Crenshaw and Persian melons, muskmelons, watermelons, tomatoes, peppers,
broccoli, cabbage, and cauliflower (58).
APPLICATION METHOD(S): Betasan should be used prior to germination of
weed seeds. It should be applied to established grass lawns prior to
planting, at the time of planting, or on established dichondra lawns.
The compound must be watered into the soil after application. Care
should be exercised if reseeding with grass is planned following
Prefar should be applied by preplant incorporation 2.5 to 5 cm (1-2
inches) deep, or preemergence followed by sprinkler or furrow irrigation
Bensulide provides long residual control of the weeds for which it
is registered (58).
Important Weeds Controlled:
Smooth and hairy crabgrass, watergrass, fall panicum, annual
bluegrass, jungle rice, silver crabgrass, foxtail, pigweed, goosegrass,
purslane, and others (8b).
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C14 H24 NO4 PS3 (62)
MOLECULAR WEIGHT: 397.5 (62)
PHYSICAL STATE: Colorless solid (99% pure); amber solid or
supercooled liquid (technical grade, 98% pure)
MELTING POINT: 34.4 C (99% pure) (62); supercools readily (pure
BOILING POINT: Decomposes (Betasan technical) (29r).
VAPOR PRESSURE: 0.001 microns at 25 C (Betasan technical) (29r).
SOLUBILITY: 25 ppm in water at 20 C (Betasan technical) (29r).
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: NA
A. ACUTE TOXICITY
DERMAL: Betasan technical: LD50 in rabbits, approximately
4 g/kg. Toxicity was not observed in rabbits at
1000 mg/kg. Non-irritating to the skin of rabbits
Betasan 3.6-G: The acute dermal LD50 is greater
than 5000 mg/kg in rabbits. A single dermal
application of 5000 mg/kg produced a mild decrease
in physical activity in rabbits. Nonirritant to
rabbit skin following a 24-hour exposure (29t).
Betasan 4-E: The acute dermal LD50 is greater than
4640 mg/kg in rabbits. A single dermal application
of 4640 mg/kg did not produce signs of toxicity in
Mild irritant to rabbit skin.
Application of 18 ml to rabbit skin (9.1 ml/kg),
caused plasma (53%) and erythrocyte (58%)
cholinesterase inhibition, 8-24 hours after
dosing. A volume of 10 ml per animal (5.2 ml/kg)
did not cause any inhibition of erythrocyte
Rabbits received fifteen daily doses during a
three week period. The doses were 0.5, 0.25 and 0.1
ml/kg/day. Erythrocyte cholinesterase activity was
inhibited about 25-60 percent at the high dose
level. Plasma cholinesterase was unaffected.
Pyelonephritis occurred in all treated groups.
Rabbits were treated once daily for a total of
12 doses during a three week period. Doses were 2.0,
1.0 and 0.5 ml/kg. Erythrocyte cholinesterase was
inhibited completely in all treated animals by the
first week and plasma cholinesterase was inhibited
by 40 to 60 percent (29s).
ORAL: LD50 = 271-1470 mg/kg. Single oral exposures of
215 to 4649 mg/kg produced salivation, lacrimation,
urination, diarrhea, dyspnea, depression and
mortality (Betasan technical) (29n).
LD50 = 826-1778 mg/kg (rat, Betasan 4-E) (29s).
The acute oral LD50 is greater than 1000 mg/kg
in female and male rats. A single oral dose of 1000
mg/kg produced a mild decrease in physical activity
in male and female rats (Betasan 3.6-G) (29t).
INHALATION: LC50 in rats, greater than 3.07 mg/l for 1-hour
exposure. No signs of toxicity were observed at
3.07 mg/l (Betasan technical) (29r).
EYES: Mild to moderate irritant to rabbit eyes (Betasan
4-E) (29s). Moderate irritant to rabbit eyes
(Betasan 3.6-G) (29t).
B. SUBACUTE AND CHRONIC TOXICITY:
Daily ingestion of 625, 1250 and 2500 ppm in the diet by dogs for 14
weeks resulted in a no-effect level at 625 ppm, minimal hepatic
cellular changes at 1250 ppm and reduced body weight, elevated serum
enzyme levels and moderate degenerative hepatic changes at 2500 ppm.
Daily ingestion of 4 and 12 mg/kg/day by dogs for 14 weeks resulted
in moderate inhibition of plasma cholinesterase at 4 and 12 mg/kg.
Daily ingestion of 20, 40, 80 160 and 320 mg/kg/day by mice for 6
weeks resulted in decreased food consumption and body weight at 32 mg/kg.
Daily ingestion of 10 and 30 mg/kg/day by mice and 100 mg/kg/day by
female mice for 12 months was without observable effect. Daily
ingestion of 100 mg/kg/day by male mice for 12 months resulted in very
slight to slight multi focal hepatocellular hypertrophy.
Daily ingestion of 12.5, 25 and 50 mg/kg/day by rats for 14 weeks
resulted in no significant changes at 12.5 and 25 mg/kg, and slight
hepatic and renal changes observed by histopathology at 50 mg/kg.
Daily ingestion of 5 or 15 mg/kg/day by rats for 13 weeks resulted
in transient inhibition of plasma cholinesterase. Negative in
bacterial mutagenicity assay without activation (Betasan technical)
IV. ENVIRONMENTAL CONSIDERATIONS
Behavior In Or On Soils
1. Adsorption and leaching characteristics in basic soil types:
Bensulide is inactivated in soils containing high amounts of
organic matter. Bensulide leaches very little in sand, clay
or organic soils.
2. Microbial breakdown: Bensulide is degraded slowly in the soil by
3. Loss from photodecomposition and/or volatilization: When applied
to the soil surface there is very little if any loss bu
volatilization, but there is a small amount of
photodecomposition in a period of several days.
4. Resultant average persistence at recommended rates: The half life
in moist loam soil at 21 to 27 C (70 to 80 F) was 4 months.
In a moist loamy sand soil at 21 to 27 C (70 to 80F) the half
life was 6 months (58).
General toxicity to wildlife and fish:
a. The 96-hr LC50 of technical bensulide in the common goldfish
is 1 to 2 ppm.
b. The 96-hr EC50 (loss of equilibrium or death) of bensulide
in the brown shrimp (P. azetucus) is in excess of 1 ppm
(the highest concentration tested).
c. The 96-hr EC50 (shell growth inhibition) of bensulide in the
common oyster (C. virginica) is 0.45 ppm.
d. The 96-hr LC50 of bensulide in the rainbow trout is 0.72 ppm.
e. The 48-hr TL of bensulide in the juvenile estuarine species
L. xanthrus) is 0.32 ppm.
f. A 21-day dietary feeding study was conducted in the Japanese
quail. A no-effect level was established at 10 ppm (58).
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 sub-
stitute for a more exhaustive review of the literature nor for the
judgement of a physician or other trained professional.
If poisoning is suspected, do not wait for symptoms to develop.
Contact a physician, the nearest hospital, or the nearest Poison
SYMPTOMS OF POISONING: Expected to be typical of organophosphorous
poisoning. No confirmed cases in man (58).
SKIN CONTACT: Immediately remove contaminated clothing under a
safety shower. Flush all affected areas with large amounts of water
for at least 15 minutes. Do not attempt to neutralize with chemical
agents. Obtain medical advice immediately (Betasan technical, Betasan
4-E) (29r,s). Immediately flush all affected areas with water for at
least 15 minutes while removing any contaminated clothing. Seek
medical attention if irritation occurs (Betasan 3.6-G) (29t).
INGESTION: If swallowed -- immediately dilute the swallowed
material by rapidly giving large quantities of water or milk, if
available, and induce vomiting by gagging the victim with a finger or
blunt object placed on the back of the victim's tongue. Continue fluid
administration until vomitus is clear. Never give anything by mouth to
an unconscious person. Call a physician or the nearest Poison Control
Center immediately (Betasan technical) (29r).
If swallowed -- immediately dilute the swallowed material by
giving large quantities of water and induce vomiting by gagging the
victim with a finger or blunt object placed on the back of the victim's
tongue. Continue fluid administration until vomitus is clear. Never
give anything by mouth to an unconscious person. Call a physician or
the nearest Poison Control Center immediately (Betasan 3.6-G) (29t).
DO NOT induce vomiting. This product contains hydrocarbon solvent.
Immediately give large quantities of water. If vomiting does occur,
give fluids again. Never give anything by mouth to an unconscious
person. Call a physician or the nearest Poison Control Center
immediately (Betasan 4-E) (29s).
INHALATION: Remove from contaminated atmosphere. If breathing
has ceased, clear the victim's airway and start mouth-to-mouth
artificial respiration, which may be supplemented by the use of a
bag-mask respirator, or a manually triggered oxygen supply capable of
delivering 1 liter/second or more. If the victim is breathing, oxygen
may be administered from a demand-type or continuous flow inhalator,
and preferably with a physician's advice. Contact a physician
immediately (Betasan 3.6-G, 4-E) (29t,s).
EYE CONTACT: Immediately flush the eyes with large quantities of
running water for a minimum of 15 minutes. Hold the eyelids apart
during the irrigation to ensure flushing of the entire surface of the
eye and lids with water. Do not attempt to neutralize with chemical
agents. Obtain medical attention as soon as possible. Oils or
ointments should not be used. Continue the irrigation for an
additional 15 minutes if the physician is not immediately available
NOTES TO PHYSICIAN: Exposure to the active ingredient may cause
cholinesterase inhibition. Atropine by injection is antidotal. 2-PAM
is also antidotal when administered early and in conjunction with
VI. FIRE AND EXPLOSION INFORMATION
GENERAL: Flash point (TOC) 157 C; fire point, 171 C (58).
Betasan technical: An open cup flash point of 315F (29r).
Betasan 3.6-G: This material is considered noncombustible.
However, under fire conditions it may decompose to give off
toxic materials (29t).
Betasan 4-E: This material is considered combustible. Under
fire conditions, it will support cumbustion and may
decompose to give off toxic materials (29s).
FIRE FIGHTING TECHNIQUE: Vapors may be irritating to the respiratory
tract and may cause breathing difficulty and pulmonary edema. Symptoms
may be delayed several hours or longer depending upon exposure.
As in any fire, prevent human exposure to fire, smoke, fumes or
products of combustion. Evacuate nonessential personnel from the fire
When there is a potential for exposure to smoke, fumes, products
of combustion, etc., firefighters should wear full-face, self-contained
breathing apparatus and impervious clothing such as gloves, hoods,
suits and rubber boots.
Use standard firefighting techniques in extinguishing fires
involving this product -- use water, dry chemicals, foam or carbon
dioxide. If drums are NOT leaking, keep cooled with a water spray.
High pressure water hose may spread product from broken containers
increasing contamination hazards. Use of contaminated buildings, area
and equipment must be prevented until they are properly decontaminated
(Betasan 3.6-G, 4-E) (29t,s).
No incompatibilities with hard water; none known or expected with
other pesticides. No corrosiveness with mild iron, steel, tin, or
brass. Corrosive to copper (58).
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Apparently indefinite storage life under normal
ambient conditions. Photosensitivity is indeterminate (58). All food
must be kept in a separate area away from the storage/use location.
Eating, drinking, smoking and carrying of tobacco products must be
prevented in areas where there is a potential for exposure to this
material. Before eating, drinking or smoking, hands and face must be
thoroughly washed (Betasan 4-E) (29s).
PROTECTIVE CLOTHING: Skin contact with liquid or its aerosol should be
minimized through the use of suitable protective clothing, gloves and
footwear, selected with regard for use condition exposure potential.
Unprotected skin exposed to vapors, aerosol or mist should be
thoroughly washed at the end of the work shift.
Eye contact with liquid or its aerosol should be avoided through
the use of chemical safety glasses, goggles or a face shield, selected
with regard for use condition exposure potential (Betasan 4-E) (29s).
PROTECTIVE EQUIPMENT: If use conditions generate airborne aerosol,
liquid or vapor, handle this material only in open (e.g. outdoor) or
well-ventilated areas. Where adequate ventilation is not available,
use NIOSH-approved respirators to reduce exposures. Respirator
selection must address the potential for exposure under the use
conditions (Betasan 4-E) (29s).
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
Make sure all personnel involved in spill are aware of the hazards
associated with this material.
A small spill can be handled routinely considering the physical
and hazardous properties of the product as well as the location of the
spill. Use adequate ventilation and wear an air supplied respirator to
prevent inhalation contact. Wear protective clothing to prevent skin
and eye contact. Soak up pooled liquid as follows:
1. If Betasan is in the liquid state: spread a suitable absorbent
such as clay on the liquid.
If Betasan is in the solid state: sweep up the powder being
careful not to create dust.
2. Place sweepings in an open drum.
3. Generously cover the contaminated area with a common household
detergent (e.g. TIDE). Using a stiff brush, work the detergent
into the spill material (adding sufficient water to the solid
product) to form a slurry. Brush the slurry into cracks and
crevices; and allow to stand for 2 to 3 minutes. Be careful to
completely avoid skin or eye contact; do not splatter on one's
self or bystanders.
4. Spread absorbents on the slurried liquid, and shovel the absorbed
material into an open drum.
5. Repeat if necessary.
6. Flush area with water, while observing proper environmental
7. Seal drum and dispose of contaminated material in an approved
8. This product is toxic to fish. Do not contaminate water by
cleaning of equipment or disposal of wstes.
Large spills must be handled according to a predetermined plan. For
assistance in developing a plan, contact Stauffer's Agricultural
Chemical Division, Westport, CT 06880 (29r).
X. LITERATURE CITED
8b. Thomson, W.T. 1981. Agricultural chemicals - book 2:
herbicides. Revised ed. Thomson Publications, Fresno, CA.
29r. Stauffer Chemical Company, Agricultural Chemical Division. 1978.
Product safety information: Betasan Technical. Westport, CT.
29s. Stauffer Chemical Company, Agricultural Chemical Division. 1980.
Product safety information: Betasan 4-E. Westport, CT.
29t. Stauffer Chemical Company, Agricultural Chemical Division. 1980.
Product safety information: Betasan 3.6-G. Westport, CT.
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.