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chloroxuron (Tenoran) Herbicide Profile 2/85

                                    chloroxuron
      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
      celery (58).
                                   I.  EFFICACY
           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
      Blue-green algae
      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
      (24j).
                             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
      TOXICOLOGY
           A.  ACUTE TOXICITY
               DERMAL:  LD50 = >10,000 mg/kg (rabbit, technical material) (56)
                        LD50 = >3000 mg/kg (rat), slight irritant to skin of
                          rabbits (62).
               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
      honeybees (62).
           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
      Control Center.
      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
      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
           cathartic (25).
           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
           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 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
                              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 to 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
           Nonflammable (58).
                                VII.  COMPATIBILITY
           Noncorrosive (58).
                            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
                                  (800) 424-9300
                      PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
                               X.  LITERATURE CITED
       8b. Thomson, W.T.  1981.  Agricultural chemicals - book 2:
               herbicides.  Revised ed.  Thomson Publications, Fresno, CA.
               274 pp.
      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.
      2/21/85