dichlobenil (Casoron) Herbicide Profile 2/85
CHEMICAL NAME: 2,6-dichlorobenzonitrile (56)
TRADE NAME(S): Casoron (56)
FORMULATION(S): Granules (Casoron G-2%, G-4%, G-6.75%, G-10%;
Norosan 4G, 10G) wettable powder (Casoron WP-50%,
Norosac 50W) (56).
TYPE: Benzonitrile herbicide
BASIC PRODUCER(S): Duphar B.V.
1077 AR Amsterdam, The Netherlands
P.O. Box 4090
Kansas City, MO 64101
STATUS: General use
PRINCIPAL USES: Casoron for selective weed control in cranberry
bogs, ornamentals, nurseries, fruit orchards, vineyards, forest
plantations, public green areas, and for total weed control (industrial
sites, railway lines, etc. under asphalt). Controls aquatic weeds in
non-flowing water (56).
APPLICATION METHOD(S): Application between sowing and emergence of crop
usually gives rise to prohibitive phytotoxicity, especially with small-
seeded crops. With a number of relatively large-seeded crops (e.g.,
corn, cotton, wheat), when planted rather deeply, there is marginal
Over established crops dichlobenil can be applied, either as a
dispersible or wettable powder or as granules, as a ground or aerial
application. The product must always be applied to the soil. For total
weed control and for weed control under trees, dichlobenil should be
applied to the soil. Under circumstances of high water evaporation
from the soil (high temperature, wet soil, low relative air humidity)
dichlobenil can evaporate very rapidly. From dry soil the evaporation
of dichlobenil is dependent on soil types and temperature. To enhance
the herbicidal effect under natural conditions the best time for
application is on dry soil just before rainfall. An increase in
herbicidal effectiveness can also be obtained by incorporation
(mechanically or by irrigation), preferably after application on dry
soil. The herbicide should be used postemergence of postplanting
to the crop (58).
CASORON G-4 is recommended for control of annual grassy and broadleafed
weeds and certain perrennial weeds:
Annual Bluegrass Foxtail Ragweed
(Poa annua) Gisekia Red Deadnettle
Artemisia Groundsel Redroot Pigweed
Bluegrass Henbit Rosarypea
Bull Thistle Horsetail Russian Knapweed
Camphorweed Jerusalemoak Russian Thistle
Canada Thistle Goosefoot Shepherdspurse
Carpetweed Knotweed Smartweed
Chickweed Lambsquarters Spanishneedles
Citron Melon Leafy Spurge Spurge
Coffeeweed Maypops Teaweed
Crabgrass Milkweed Vine Texas Panicum
Cudweed (Morrenia odorata) (Hurrahgrass)
Curly Dock Miners lettuce Timothy
Dandelion Natalgrass Wild Artichoke
Dogfennel Old Witchgrass Wild Aster
Eveningprimrose Orchardgrass Wild Barley
Falsedandelion Peppergrass Wild Carrot
(Catsear) Pineappleweed Wild Mustard
Fescue Plantain Wild Radish
Fiddleneck Purslane Yellow Rocket
Florida Purslane Quackgrass Yellow Woodsorrel
Casoron G-10 aquatic granules effectively control these weeds in ponds,
lakes and recreation waters:
Sago Pondweed Potamogeton pectinatus
Northern Watermil Foil Myriophyllum exalbescens
American Pondweed Potamogeton nodosus
Waterthread Pondweed Potamogeton diversifolius
Coontail Ceratophyllum demersum
American Elodea E. canadensis
Slender Naiad Najas flexilis
Leafy Pondweed Potamogeton foliosus
Chara C. vulgaris (60b)
Deep rooted plants are tolerant. Control may last for the entire
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C7 H3 Cl2 N (62)
MOLECULAR WEIGHT: 172.0 (62)
PHYSICAL STATE: White crystalline solid (pure compound) (58);
colorless to off-white crystalline solid (technical
grade; >,=, 94% pure) (62).
ODOR: Aromatic odor (pure compound) (58)
MELTING POINT: 145-146 C (pure compound); 139-145 C (technical
BOILING POINT: 270.0 to 270.1 C at 760 Hg pressure (pure
VAPOR PRESSURE: 5.5 x 10-4 mmHg at 20 C (pure compound) (58)
SOLUBILITY: 18 ppmw at 20 C (pure compound); 25 ppmw at 20 C
(technical material) (58).
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: NA
A. ACUTE TOXICITY
DERMAL: LD50 = 1350 mg/kg (albino rabbit) (62).
ORAL: LD50 = 3160 mg/kg (rat); >2460 mg/kg (male mouse)
LD50 = greater than or equal to 3160 mg/kg (male
and female rats), 2126 mg/kg (male mouse),
2056 mg/kg (female mouse) (62).
B. SUBACUTE AND CHRONIC TOXICITY:
In 2-yr feeding trials and a 3-generation feeding study NEL for
rats was 20 mg/kg diet. In 84-day feeding trials NEL for rats and
rabbits was 50 mg/kg diet (62).
Rats fed 50 ppm in their diet for 3 months showed no deviations
from normal. In pigs fed 50 ppm in their diet for 6 months, no unusual
effects were found (58).
Tests on chronic toxicity of dichlobenil, including reproduction
tests, liver function tests, and an investigation into teratogenic
effects have been conducted. The lowest no toxic effect level found
was 20 ppm on rats (58).
The subacute 21-day dermal LD50 of dichlobenil on albino rabbits
is 500 mg/kg per day. The no-effect level was 100 mg/kg per day. No
significant local skin reactions were noted among animals at any of the
dose levels tested (58).
IV. ENVIRONMENTAL CONSIDERATIONS
LC50 (8-day) was: for Japanese quail >5000 mg/kg diet; for pheasant
c. 1500 mg/kg diet. LC50 (48-hr) is: for guppies >18 mg/l; for water
fleas 9.8 mg/l (62).
No adverse effects on wildlife have been noticed in the tests for
the herbicidal evaluation of the product. Neither does the observed
toxicity for mammals make it probable to expect such effects on
wildlife mamals. Dichlobenil is not acutely toxic to fish at
herbicidal concentrations. The range of the LC50 is 10 to 20 ppmw for
pumpkinseed (Lepomis gibbosus), bluegill (L. macrochirus), and large
mouth bass (Micropterus salmoides). A dispersible powder formulation
was tested and resulted in a TLM to bluegill sunfish of 17 ppm for both
24 and 48 hr. The granular material of the same formulation resulted
in a TLM of 37 ppm (58).
Behavior In or On Soils
1. Adsorption and leaching characteristics in basic soil types:
Downward movement of dichlobenil with water through the soil is
extremely slow due to its water solubility and adsorption on soil
constituents. There is some additional transport of dichlobenil
due to diffusion in the vapor phase. Soils with high humus
contents need higher dosages. This can be explained by the fact
that the adsorption of dichlobenil on soils is dependent on their
contents of organic matter. In pure sand and on clay the
adsorption is rather low.
2. Microbial breakdown: In soils dichlobenil is gradually broken
down microbiologically into 2,6-dichlorobenzamide. The rate of
this process depends on the soil type. In laboratory experiments
with eight different soil types the half life of dichlobenil
varied between 1.5 and 12 months.
The benzamide, being more soluble than dichlobenil is leached
down, and in addition it is slowly broken down via
3. Loss from photodecomposition and/or volatilization: Because of
the relatively high volatility of dichlobenil and its
co-distillation properties with water, loss of dichlobenil from
the soil surface can be rapid.
4. Resultant average persistence at recommended rates: Applications
using normal herbicidal rates remain effective for a period of 2
to 6 months, under favorable conditions even for a period of 1
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
respiratory tract (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:
A. 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.
B. Activated Charcoal - Administer 30-50 gm as a slurry in tap
water, after vomiting stops.
C. Sodium or Magnesium Sulfate, 0.25 gm/kg in tap water, as a
EYE CONTACT: Flush contaminated eyes with copious amounts of
fresh water for 15 minutes (25).
NOTES TO PHYSICIAN:
1. INGESTIONS of LARGE amounts (more than 10 mg/kg) occurring less
than an hour before treatment, should probably be treated by
A. INTUBATE stomach and ASPIRATE contents.
B. LAVAGE stomach with slurry of ACTIVATERD CHARCOAL in 0.9%
saline. Leave 30-50 gm activated charcoal in the stomach
before withdrawing tube.
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 precautions:
(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.
2. 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.
3. 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
VI. FIRE AND EXPLOSION INFORMATION
The formulated product is nonflammable (58).
Dichlobenil as a suspension in water does not deteriorate. It is
compatible with most wettable powder herbicides. Mixing with
water-soluble fertilizers or emulsifiable herbicides is not recommended.
The wettable powder and granular formulations are essentially
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Harmful if swallowed. Do not breathe dust. Do
not allow contact with eyes or skin. Use with caution. Avoid
contamination of food and feed stuffs. Keep out of reach of children.
Do not apply during period of high soil temperature without immediate
incorporation. On sandy soils lower dosages should be applied. The
shelf life in storage is at least 2 years when stored in a cool, dry
place. In view of its volatility, the product should be packed in
tightly closed containers. The chemical is thermally stable. Very
little degradation occurs on exposure to daylight (58).
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.
25. Morgan, D.P. 1982. Recognition and management of pesticide
poisonings, 3rd ed. U.S. Environmental Protection Agency,
Washington, DC. 120 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.
60a. Thompson-Hayward Chemical Company. 1980. Casoron herbicide
pamphlet. Kansas City, KS.
60b. Thompson-Hayward Chemical Company. 1971. Aquatic weed control
research report (Casoron G-10). Kansas City, KS.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.