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dichlobenil (Casoron) Herbicide Profile 2/85

                                    dichlobenil
      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.
                          Apollolaan 151
                          1077 AR Amsterdam, The Netherlands
                          PBI-Gordon Corp.
                          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
      selectivity.
      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).
                                   I.  EFFICACY
      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
        (Pusley)                                                       (60a)
      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
      season (8b).
                             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
                           product) (62).
      BOILING POINT:       270.0 to 270.1 C at 760 Hg pressure (pure
                           compound) (58)
      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
      TOXICOLOGY
           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
           2,6-dichlorobenzoic acid.
      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
           year (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:  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
               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 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
           promptly (25).
                        VI.  FIRE AND EXPLOSION INFORMATION
           The formulated product is nonflammable (58).
                                VII.  COMPATIBILITY
           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
      noncorrosive (58).
                            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
                                  (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.
      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.
      2/20/85