alachlor (Lasso) Herbicide Profile 6/85
CHEMICAL NAME: 2-Chloro-2'-6'-diethyl-N-(methoxymethyl)-acetanilide
TRADE NAME(S): Lasso (56)
FORMULATION(S): Emulsifiable concentrate (4 pounds/gallon), granules
TYPE: Acetanilide herbicide
BASIC PRODUCER(S): Monsanto Agricultural Products Co.
800 N. Lindbergh Blvd.
St. Louis, MO 63166
STATUS: General use. A Special Review of all pesticide
products containing the active ingredient alachlor was initiated
on January 9, 1985. The EPA has determined that alachlor produces
tumors in laboratory rats and mice and that humans can be exposed
to alachlor through consumption of treated crops, consumption of
water, or contact during handling and use as a pesticide.
As a result of the the Special Review and the reregistration process,
the following label changes have been made:
-- Lasso will no longer be approved for use with potato crops or
in aerial applications.
-- Use rates of 6 to 8 pounds per acre for soybeans, formerly
recommended for certain unusual soil conditions, have also
been removed from the label.
-- The new label requires goggles or face shield, rubber gloves,
long trousers, long sleeved shirt or jacket of tightly woven
material along with boots high enough to cover ankles when
transferring and mixing, and when adjusting, repairing or
cleaning equipment. Wear rubber boots when pouring from
open containers or when re-entry is made into fields where the
product has been applied thriugh center pivot irrigation and the
field is still wet.
The new label also includes new instructions on mixing, spraying
-- Because of EPA concern over groundwater in general and the low
level finding of alachlor in water, precautionary steps against
potential water contamination are described in new label statements.
-- The new label encourages growers to obtain information on careful
handling and use practices.
PRINCIPAL USES: For controlling many annual grasses and certain
broadleaf weeds in soybeans, corn, peanuts, dry beans, sunflowers,
milo. Leaves no residue in soil to carry over to the next
year. Can be broadcast, banded or applied by ground
equipment in water or sprayable fluid fertilizers, or impregnated on
dry bulk fertilizer, preplant incorporated or preemergence as directed
on the label (56).
To be developed.
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C14 H20 Cl NO2 (62)
MOLECULAR WEIGHT: 269.8 (62)
PHYSICAL STATE: Cream-colored solid (pure compound) (62)
ODOR: Odorless (pure chemical) (58)
MELTING POINT: 39-41.5 C (pure compound) (62); 39.5-41.5 C
BOILING POINT: 100 C at 0.02 mmHg, 135 C at 0.3 mmHg (pure
DECOMPOSITION TEMPERATURE: 105 C (pure compound) (62)
VAPOR PRESSURE: 2.2 x 10-5 mmHg at 25 C, 0.02 mmHg at 100 C (pure
SOLUBILITY: 242 mg/l water at 25 C (pure compound) (62)
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: NA
A. ACUTE TOXICITY
DERMAL: a. Technical alachlor
Rabbit acute dermal LD50 - 13,300 mg/kg
Rabbit skin irritation - 1.9 on a scale of 8.0,
Rabbit acute dermal LD50 - 7800 mg/kg
Rabbit skin irritation - 4.8 on a scale of 8.0,
c. Lasso EC
Rabbit acute dermal LD50 - 8,000 mg/kg
Rabbit skin irritation - 3.2 on a scale of 8.0,
d. Lasso II
Rabbit acute dermal LD50 - 16,000 mg/kg,
practically non-toxic by single dermal
Rabbit skin irritation - 1.2 on a scale of 8.0,
slightly irritating (58)
ORAL: a. Technical alachlor
Rat acute oral LD50 - 930 mg/kg
Rat acute oral LD50 - 2000 mg/kg
c. Lasso EC
Rat acute oral LD50 - 1000 mg/kg
d. Lasso II
Rat acute oral LD50 - 5800 mg/kg (58)
INHALATION: LC50 = >32 mg/l air for 1 hr - no adverse effects
noted during 14 days of observation (rat, Lasso
EYES: a. Technical alachlor
Rabbit eye irritation - 0.4 on a scale of 110.0,
Rabbit eye irritation - 44.6 on a scale of 110.0,
c. Lasso EC
Rabbit eye irritation - 41.0 on a scale of 110.0,
d. Lasso II
Rabbit eye irritation - 21.6 on a scale of 110.0,
slightly irritating (58)
B. SUBACUTE AND CHRONIC TOXICITY:
Growth patterns were normal with technical fed to rats and beagle
dogs at levels of 20, 200, and 2,000 ppm for a 90-day period. Animals
fed at the 2,000 ppm level exhibited some growth depression, and
weights of male dogs were below normal (54).
IV. ENVIRONMENTAL CONSIDERATIONS
Eight-Day Feeding LC50 - 10-15 day old mallard ducklings -
greater than 5000 ppm
10-15 day old bobwhite quail chicks -
greater than 5,000 ppm
b. Aquatic organisms - technical
96 hour LC50 in Rainbow Trout - 1.8 mg/l
96 hour LC50 in Bluegill Sunfish - 2.8 mg/l
48 hour EC50 in Daphnia magna - 10 mg/l
96 hour LC50 Rainbow Trout - 4.2 mg/l
96 hour LC50 Bluegill Sunfish - 6.4 mg/l
48 hour EC50 Daphnia magna - 35 mg/l (58)
Behavior In or On Soils
1. Adsorption and leaching characteristics in basic soil types:
Adsorbed by soil colloids.
2. Microbial breakdown: Main method of degradation.
3. Loss from photodecomposition and/or volatilization: Low.
4. Resultant average persistence of recommended rates: 6 to 10 weeks
but may vary depending on soil type and climatic conditions (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
KNOWN OR SUSPECTED ADVERSE EFFECTS: Mild irritant (25).
SKIN CONTACT: Wash contaminated skin with soap and water (25).
INGESTION: Ingestions of small amounts (less than 10 mg/kg body
weight) occurring less than an hour before treatment, are probably best
treated by: Syrup of Ipecac, followed by 1-2 glasses of water. Dose
for adults and children over 12 years: 30 ml. Dose for children under
12 years: 15 ml (25).
EYE CONTACT: Flush contaminated eyes with copious amounts of
fresh water for 15 minutes (25).
NOTES TO PHYSICIAN:
INGESTIONS of LARGE amounts (more than 10 mg/kg) occurring less than an
hour before treatment, should probably be treated by gastric lavage:
A. INTUBATE stomach and ASPIRATE contents.
B. LAVAGE stomach with slurry of ACTIVATED CHARCOAL in 0.9% saline.
Leave 30-50 gm activated charcoal in the stomach before
C. SODIUM SULFATE, 0.25 gm/kg in tap water, as a cathartic.
CAUTION: Hydrocarbons (kerosene, petroleum distillates) are
included in some formulations of these chemicals.
Ingestion of very LARGE AMOUNTS may cause CNS
depression. In this case, IPECAC IS CONTRAINDICATED.
Also, gastric intubation incurs a risk of HYDROCARBON
PNEUMONITIS. For this reason observe the following
(1) If the victim is unconscious or obtunded and
facilities are at hand, insert an ENDOTRACHEAL TUBE
(cuffed, if available) prior to gastric intubation.
(2) Keep victim's HEAD BELOW LEVEL OF STOMACH during
intubation and lavage (Trendelenburg, or left
lateral decubitus, with head of table tipped
downward). Keep victim's head turned to the left.
(3) ASPIRTE PHARYNX as regularly as possible to remove
gagged or vomited stomach contents.
INGESTIONS occurring MORE THAN an HOUR before treatment are probably
best treated only by ACTIVATED CHARCOAL, 30-50 gm and SODIUM or
MAGNESIUM SULFATE, 0.25 gm/kg, as described above.
There are no specific antidotes for these chemicals. Because
manifestations of toxicity do occasionally occur in peculiarly
predisposed individuals, MAINTAIN CONTACT with victim for at least 72
hours so that unexpected adverse effects can be treated promptly (25).
VI. FIRE AND EXPLOSION INFORMATION
Compatible with water of 1,000 ppm hardness or less; usually
compatible with sprayable fluid fertilizers. No corrosion to No. 316
and No. 304 stainless steel, aluminum and heresite. Corrosive to steel
and black iron (58).
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Do not store near heat or open flame. Avoid
contact with eyes and skin. Wash thoroughly after handling (58).
Store above 32 F to keep product in solution. Below 32 F
crystals may form and settle to the bottom. If crystals form, place
in a warm room and roll and shake container frequently for several
PROTECTIVE CLOTHING: Wear goggles or face shield and rubber gloves
in transferring and mixing and when adjusting, repairing, or cleaning
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
X. LITERATURE CITED
25. Morgan, D.P. 1982. Recognition and management of pesticide
poisonings, 3rd ed. U.S. Environmental Protection Agency,
Washington, DC. 120 pp.
54. Weed Science Society of America, Herbicide Handbook Committee.
1979. Herbicide handbook of the weed science society
of America, 4th ed. Weed Science Society of America,
Champaign, IL. 479 pp.
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.
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