chloroxuron (Tenoran) Herbicide Profile 2/85
CHEMICAL NAME: 3-[p-(p-chlorophenoxy)phenyl]-1,1-dimethylurea (56)
TRADE NAME(S): Tenoran (56)
FORMULATION(S): 50% wettable powder (8b)
TYPE: Urea-derivative herbicide
BASIC PRODUCER(S): Ciba-Geigy Corp.
P.O. Box 18300
Greensboro, NC 27419
STATUS: General use
PRINCIPAL USES: Most annual grasses and broadleaf weeds are
controlled with no geographical limitations where sufficient moisture
is available for growing crops. Common crop plants for which the
compound should be useful are soy beans, onions, strawberries, and
Germination of weed seeds is normal in soil treated with Tenoran,
but phytotoxic effects are manifested by growth inhibition and chlorotic
and necrotic effects on leaves.
Tenoran destroys freshly germinated seeds and is most effective for
weed control after cotyledons have opened.
Tenoran is effective for weed control when applied as a preemergence
broadcast or band treatment to the surface of the soil at the time of
planting, and as a postemergence treatment to tolerant crops. Tenoran
may be applied postemergence either before or after weeds germinate,
but for best results, applications should be made before weeds are 1 to
2 inches high. As a general rule, the smaller the weed the easier they
are to kill.
Moisture conditions have a marked effect on the preemergence
performance of Tenoran for weed control. In experiments where
extremely dry weather conditions prevailed, the herbicidal activity of
Tenoran was reduced markedly. Under dry conditions, the soil should be
irrigated as soon as possible after preemergence treatment.
Tenoran at rates of 3.0 to 6.0 pounds active ingredient per acre
(ai/A) applied as a preemergence or postemergence treatment and/or 1.0
to 1.5 lb ai/A + 0.5% surfactant Adjuvan-T postemergence controlled the
following weed species:
Common Name Scientific Name
American pondweed Potamogeton nodosus
Annual sedge Cyperus dentatus and C. diandrus
Barnyardgrass Echinochloa crusgalli
Black nightshade Solanum nigrum
Brachiaria Brachiaria platyphylla
Carpetweed Mollugo verticillata
Cocklebur Xanthium sp.
Common morningglory Ipomoea purpurea
Corn cockle Agrostemma githago
Crowfootgrass Dactyloctenium aegyptium
Dandelion (seedlings) Taraxacum officinale
Fall panicum Panicum dichotomiflorum
Florida pusley Richardia scabra
Goosegrass Eleusine indica
Jimsonweed Datura stramonium
Lambsquarters Chenopodium album
Large crabgrass Digitaria sanguinalis
Palmer amaranth Amaranthus palmeri
Prostrate pigweed Amaranthus graecizans
Puncturevine Tribulus terrestris
Purslane Portulaca oleracea
Ragweed Ambrosia artemisiifolia
Redroot pigweed Amaranthus retroflexus
Shepherdspurse Capsella bursa-pastoris
Sicklepod Cassia obtusifolia
Smallflower morningglory Jacquemontia tamnifolia
Smartweed Polygonum sp.
Smooth crabgrass Digitaria ischaemum
Smooth pigweed Amaranthus hybridus
Southern naiad Najas guadalupensis
Spiny pigweed Amaranthus spinosus
Stonewort alga Chara sp. and Nitella sp.
Swinecress Coronopus didymus
Tumble pigweed Amaranthus albus
Velvetleaf Abutilon theophrasti
Wild mustard Brassica kaber
Tenoran is not effective for the control of established perennial weeds
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C15 H15 Cl N2 O2 (62)
MOLECULAR WEIGHT: 290.7 (62)
PHYSICAL STATE: Colorless powder (pure compound) (62)
ODOR: Odorless (pure compound) (58)
MELTING POINT: 151-152 C (pure compound) (62); 149-150 C
(pure compound) (58).
VAPOR PRESSURE: 239 nPa at 20 C (pure compound) (62)
SOLUBILITY: 4 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 = >10,000 mg/kg (rabbit, technical material) (56)
LD50 = >3000 mg/kg (rat), slight irritant to skin of
ORAL: LD50 = 3700 mg/kg (rat, technical material) (56)
LD50 = 3700 mg/kg (male rat); 5400 mg/kg (female rat);
>10,000 mg/kg (dog) (58).
LD50 = 2.7 g/kg (rat; 50% WP, based on a.i.) (24j).
LD50 = 3000 mg tech./kg (rat) (62)
INHALATION: LC50 (6-hr) for rats >1350 mg/m3 air (62)
EYES: Nonirritating (rabbit, technical material) (56)
Slight irritant to eyes of rabbits (62).
B. SUBACUTE AND CHRONIC TOXICITY:
In 120-day feeding trials NEL for rats was 30 mg/kg daily; in
90-day trials in dogs 400 mg/kg diet (16.7 mg/kg daily) (62).
Chloroxuron caused no effect either locally or systemically in
albino rabbits treated daily for 10 days with 5 ml of a 10% suspension
of chloroxuron 50WP (58).
IV. ENVIRONMENTAL CONSIDERATIONS
LC50 is: for rainbow trout >100 mg/l; for crucian carp >150 mg/l;
for bluegill 28 mg/l. Slightly toxic to birds, practically non-toxic to
The LC50 of chloroxuron to killfish (Oryzias latipes) is >15 ppm.
At 0.4 ppm (2 lb/surface acre) it does not cause mortality to fathead
minnows (Timephales promelas), and had no effect on reduction at 8
weeks after application (58).
Behavior In Or On Soils
1. Adsorption and leaching characteristics in basic soil types:
Chloroxuron is quite strongly adsorbed on soil particles and this
seems to be an important factor in controlling its availability in
soil solution and determining both the initial toxicity and the
residual activity in some types of soils. The following
concentrations of chloroxuron adsorbed were in equilibrium with 1
ppm soil solutions: 14 ug/g (sandy loam), 40 ug/g (clay loam, and
110 ug/g (humus soil). With soil columns (sandy, clay, and humus
soils) and simulated rain (200 mm in 45 hr), the bulk of
chloroxuron was not removed from the top 1-cm layer of all three
soils. Leaching does not appear to be a factor in removing
chloroxuron from the surface of soil.
2. Microbial breakdown: Bacterial suspensions derived from humus
soil metabolize chloroxuron to the monomethylated, dimethylated,
and the (4-chlorophenoxy)aniline derivatives.
3. Loss from photodecomposition and/or volatilization: Under model
conditions (irradiation with ultraviolet source of 300W),
photodestruction of chloroxuron is rapid (90% loss within 13 hr).
4. Resultant average persistence at recommended rates: The rate of
breakdown of chloroxuron is slightly higher in sandy loam (35%
loss in 18 weeks) than in humus soil (25% loss) under optimum
growth conditions. In humus soil, microbial breakdown and
adsorption are contributing factors in controlling the period of
herbicidal activity of chloroxuron. Chloroxuron applied at 8 lb/A
to a sandy soil caused no phytotoxicity to cotton, corn, or
peanuts planted 6 months after application; ranfall was 4.6 inches
during the 6-month period (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: Many substituted ureas are
moderately irritating to skin, eyes, and mucous membranes (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
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 ACTIVATED 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 avalable) prior to gastric
(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
(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 to 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
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Keep out of the reach of children and animals.
May be harmful if swallowed. Wash hands with soap and water before
eating, drinking, or smoking. Do not contaminate food or feed. Avoid
repeated or prolonged contact with the skin. Wear clean clothing.
Wash clothes before reusing (24k).
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.
24j. CIBA Agrochemical Company, Division of CIBA Corporation. 1967.
Research bulletin No. 15: Tenoran herbicide. Vero Beach, FL.
24k. CIBA Agrochemical Company, Division of CIBA Corporation. ?
Specimen label: Tenoran 50WP herbicide. Summit, NJ.
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.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.