metolachlor (Dual) Herbicide Profile 2/85
CHEMICAL NAME: 2-chloro-N-(2-ethyl-6-methylphenyl)-N-(2-methoxy-
1-methylethyl) acetamide (56)
TRADE NAME(S): Dual, Bicep (54)
FORMULATION(S): Emulsifiable concentrate (8 pounds/gallon), 25G
TYPE: Acetamide herbicide
BASIC PRODUCER(S): Ciba-Geigy Corp., Agricultural Division
P.O. Box 11422
Greensboro, NC 27409
STATUS: General use
PRINCIPAL USES: For preemergence and preplant incorporated weed
control in corn, soybeans, peanuts, grain sorghum, potatoes, pod
crops, cotton, safflower, and woody ornamentals; also selective on
sunflowers, flax, and certain other crops (56).
Dual 6E is a selective herbicide for control of annual grass weeds,
yellow nutsedge (Cyperus esculentus), and certain broadleaf species in
Representative examples of weeds controlled include barnyardgrass
(Echinochloa crusgalli), crabgrass (Digitaria spp.), fall panicum
(Panicum dichotomiflorum), foxtails (Setaria sp.), broadleaf
signalgrass (Brachiaria platyphylla), goosegrass (Eleusine indica),
witchgrass (Panicum capillare), pigweed (Amaranthus spp.), carpetweed
(Mollugo verticillata), Florida pusley (Richardia scabra), and yellow
nutsedge (Cyperus esculentus) (54).
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C15 H22 Cl NO2 (62)
MOLECULAR WEIGHT: 283.8 (62)
PHYSICAL STATE: Colorless liquid (pure compound) (62)
Liquid, white to tan (pure chemical) (54)
ODOR: None (pure chemical) (54)
BOILING POINT: 100 C/0.001 mmHg (pure compound) (62)
VAPOR PRESSURE: 1.7 mPa at 20 C (pure compound) (62)
SOLUBILITY: 530 mg/l water at 20 C (pure compound) (62)
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: NA
A. ACUTE TOXICITY
DERMAL: LD50 = >3170 mg/kg (rat); slight irritant to skin
of rabbits (62).
LD50 = >10,000 mg/kg (rabbit, Dual 6E) (54)
ORAL: LD50 = 2780 mg tech./kg (rat) (62)
LD50 = 4286 mg/kg (male rat); 2828 mg/kg (female
rat) (Dual 6E) (54).
INHALATION: LC50 = >1750 mg/l air (rat, 4-hour exposure)
(technical); >247 mg/l air (rat, 4-hour exposure)
(Dual 6E) (54).
EYES: Non-irritant to eyes (rabbit) (62)
Moderately irritating (rabbit, Dual 6E) (54).
B. SUBACUTE AND CHRONIC TOXICITY:
In 90-day feeding trials NEL was: for rats 1000 mg/kg diet
(c. 90 mg/kg daily); for dogs 500 mg/kg diet (c. 17 mg/kg daily) (62).
IV. ENVIRONMENTAL CONSIDERATIONS
LC50 (96 hr) is: for rainbow trout 2 mg/l; for carp 4.9 mg/l;
for bluegill 15 mg/l. It is practically non-toxic to birds and
Fish species Metolachlor technical (ppm)
Rainbow trout 2.0
Bluegill sunfish 15.0
Channel catfish 4.9
8-Day Dietary LC50
Bird species Metolachlor technical (ppm)
Bobwhite quail >10,000
Mallard duck >10,000 (54)
Metolachlor is more readily adsorbed to muck or clay soils than to
soils of low clay and organic matter content. Organic matter is the
main soil constituent determining the leaching behavior of metolachlor
as it is rapidly absorbed by humic materials. High organic content
soils have less metolachlor movement than comparative soils with less
organic matter. When organic matter content approaches 2.0%, no
significant leaching would be expected, even under heavy rainfall
conditions. Also, while metolachlor movement in soil is less affected
by soil particles or the mineral portion, leaching is inhibited by high
clay and/or silt content.
It has little, if any, lateral movement in the soil, other than
being moved in physical association with soil particles. Thus, ground
water contamination as a result of metolachlor leaching is highly
Metolachlor is a nonpersistent compound in soil. Radio-labeled
studies have shown a rapid decline of the parent compound and
concurrent incorporation of the parent material and breakdown products
into the soil humic material. By 12 weeks, about 5% is converted to
There have been no significant adverse effects on soil
microorganism populations from exaggerated metolachlor rates.
Photolysis has been investigated in laboratory studies. Under
optimum exposure conditions to natural sunlight, the half-life is
approximately 8 days. Under field conditions, the half-life would be
considerably greater following a preemergence application because of
reduced exposure to sunlight resulting from soil topographic
variability. Under certain conditions, volatility may be a significant
factor in metolachlor's dissipation.
Although the soil half-life is dependent on soil type and
environmental conditions, no buildup following repeated annual
applications of metolachlor is expected.
Also, the duration of biological activity is dependent on soil and
environmental factors; however all biological evidence indicates that
metolachlor does not persist from one season to the next in sufficient
quantity to injure sensitive crops when applied at recommended rates
Approximate Residual Period: The half-life dissipation rate for
metolachlor has been determined from laboratory and field studies. In
northern areas it is 30-50 days and 15-25 days in southern areas (54).
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: Moderately irritating to skin
and eyes (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).
INHALATION: Remove from contaminated atmosphere. If symptoms
appear or person is unconscious, get medical attention (Dual 8E) (24h).
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) ASPIRATE 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 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
GENERAL: Not combustible. No hazardous decomposition products.
As in any fire, prevent human exposure to fire, smoke, fumes or
products of combustion. Evacuate nonessential personnel from the area.
Firefighters should wear impervious clothing such as gloves, hoods,
suits and rubber boots. Use of contaminated buildings, area and
equipment must be prevented until they are properly decontaminated
(Dual 8E) (24h).
EXTINGUISHER TYPE: Use standard organic chemical firefighting
techniques in extinguishing fires involving this material -- use dry
chemicals, foam or carbon dioxide (Dual 8E) (24h).
To be developed.
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Keep this material out of the reach of children.
Containers must be stored in a cool, dry, well ventilated area. Store
away from foodstuffs. All food must be kept in a separate area away
from the storage/use location. Eating, drinking and smoking should be
prevented in areas where there is a potential for exposure to this
material. This material should be handled in a well ventilated area
(Dual 8E) (24h).
PROTECTIVE CLOTHING: Skin contact with the liquid should be prevented
through the use of rubber gloves and clothing consistent with good
pesticide handling practice. Eye contact with the liquid should be
avoided through the use of chemical safety glasses or goggles (Dual 8E)
PROTECTIVE EQUIPMENT: Where adequate ventilation is not available and
exposure to excessive mists or spray could occur, wear a Conflo II
(MSA) or other approved pesticide respirator (Dual 8E) (24h).
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 cleanup follow good
industrial hygiene pratices.
Small spills can be handled routinely. Cover the spill with an
absorbent material such as vermiculite, lime, or sawdust. Sweep up the
material and place in an appropriate chemical waste container. Seal
container and dispose of in an approved landfill. Wash the spill area
with a saturated solution of sodium carbonate and a strong detergent.
Flush the spill area with water to remove any residue.
Do not reuse container. Destroy by perforation or crushing and
burying in a safe place.
Disposal of material, spill residues, wash water, and containers
must be by methods consistent with local, state and federal health and
environmental regulations (Dual 8E) (24h).
X. LITERATURE CITED
24h. Ciba-Geigy Corporation. 1982. Safety data sheet: Dual 8E.
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.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.