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methidathion (Supracide) Chemical Profile 4/85

                                    methidathion

      CHEMICAL NAME:      O,O-dimethyl phosphorodithioate, S-ester with
                          4-(mercaptomethyl)-2-methoxy-1,3,4-thiadiazolin-
                          5-one (56)

      DEC INGRED. CODE:

      TRADE NAME(S):      Supracide (1)

      FORMULATION(S):     Emulsifiable concentrate (2 pounds/gallon) (56)

      TYPE:               Organophosphate insecticide

      BASIC PRODUCER(S):  Ciba-Geigy Corp., Agricultural Division
                          P. O. Box 11422
                          Greensboro, NC 27409

      STATUS:             Restricted use

      PRINCIPAL USES:  For the control of alfalfa weevil and certain other
      insects in alfalfa, scales in citrus, spider mites, bollworm, budworm,
      lygus bug, pink bollworm, and whitefly in cotton.  Also labeled for use
      in sunflower, artichokes, apples, almonds, cherries, apricots, pears,
      nectarines, plums, prunes, walnuts, peaches and pecans, for control of
      Banks grass mite in sorghum (Texas only) (56).


                                   I.  EFFICACY

           Pests Effectively Controlled:

      Alfalfa                     Deciduous Fruit         Nursery Stock
      _______                     _______________         _____________

      alfalfa weevil              peach twig borer        pine needle scale
      aphids                      San Jose scale
      leafhoppers                 green peach aphid
      meadow spittlebugs

      Sunflowers                  Walnuts                 Ornamentals
      __________                  _______                 ___________

      sunflower moth              walnut aphid            euonmymus scale
      banded sunflower moth       frosted scale           European pine
      sunflower seed midge        walnut scale              sawfly
      sunflower maggot complex                            juniper scale
      stem weevils                                        pine bark aphid
      seed weevils                                        sod webworm
                                                          tuliptree scale
                                                          twospotted spider
                                                             mite

      Pome and Drupe Fruit
      ____________________

      apple maggot
      cherry leafminer
      codling moth
      fruittree leafroller
      green fruitworm
      oystershell scale
      plum curculio
      redbanded leafroller
      twospotted spider mite (24d)

           Mixing with alkaline materials may reduce the effectiveness.
      Residual effectiveness for three to five weeks has been noted (8a).


                             II.  PHYSICAL PROPERTIES

      MOLECULAR FORMULA:  C6 H11 N2 O4 P S3 (62)

      MOLECULAR WEIGHT:   302.3 (62)

      PHYSICAL STATE:     Colorless crystals (pure compound) (62)

      MELTING POINT:      39-40 C (pure compound) (62)

      VAPOR PRESSURE:     186 uPa at 20 C (pure compound) (62)

      SOLUBILITY:         250 mg/l water at 20 C (pure compound) (62)


                          III.  HEALTH HAZARD INFORMATION

      OSHA STANDARD:  None established

      NIOSH RECOMMENDED LIMIT:  None established

      ACGIH RECOMMENDED LIMIT:  None established

      TOXICOLOGY

           A.  ACUTE TOXICITY

               DERMAL:  LD50 = 1546 mg/kg (rat) (62)
                        LD50 = 200 mg/kg; slight skin irritation (rabbit,
                          technical product) (56).
                        LD50 = 640 mg/kg (rat, 2E formulation); severe skin
                          irritation (rabbit, 2E formulation) (56).

               ORAL:    LD50 = 25-54 mg tech./kg (rat) (62)
                        LD50 = 44 mg/kg (rat, technical product) (56)
                        LD50 = 65 mg/kg (rat, 2E formulation) (56)

               INHALATION:  LC50 = 3.6 mg/l for 4 hrs (rat, 2E formulation)
                            (56)

               EYES:    Nonirritating (rabbit, technical product); corrosive
                        (rabbit, 2E formulation) (56).

           B.  SUBACUTE AND CHRONIC TOXICITY:

           In 2-yr feeding trials NEL was: for rats 4 mg/kg diet (0.15 mg/kg
      daily); for dogs 0.25 mg/kg daily.  Human volunteers tolerated daily oral
      doses of up to 0.11 mg/kg for at least 42 days without reaction (62).


                        IV.  ENVIRONMENTAL  CONSIDERATIONS

           Under certain conditions phytotoxic to several kinds of plants.
      Check label.  Hazardous to honey bees.  Biological magnification
      unlikely.  Nonphytotoxic (1).

           In laboratory trials it is toxic to birds in chronic oral
      application; slightly toxic to honeybees (62).


      Fish Species                                96-hour LC50 (ppm)
      ____________                                __________________

      Rainbow trout                                      0.01
      Bluegill sunfish                                   0.0022
      Goldfish                                           6.8
      Catfish                                           12.0

      Bird Species                                8-day Dietary LC50 (ppm)
      ____________                                ________________________

      Mallard ducklings                                  328
      Bobwhite Quail chicks                              240         (24d)

      Animal and Plant Metabolism
      ___________________________

           It has been demonstrated that the primary route for methidathion
      metabolism in the plant is through the demethylation and hydrolysis of
      the phosphorous-sulfur linkage producing an unstable entity which
      reacts with amino acids to form thiadiazole conjugates and undergoes
      decomposition of the thiadiazole ring and its side chains.  This is
      also the primary route in animals, but the hydrolysis products can also
      be transmethylated, producing a sulfide which is not a cholinesterase
      inhibitor.  Oxidation of the sulfide to sulfoxide and sulfone (also not
      cholinesterase inhibitors) does occur and is followed by decomposition
      of the thiadiazole ring moiety.

      Environmental Fate of Methidathion
      __________________________________

           Based upon rather extensive studies, methidathion has shown no
      unreasonable adverse effects on the environment.  The compound is not
      persistent in field soils, displaying a half-life generally less than
      two weeks.  Radio-labeled studies lend support to this observation,
      showing microbial metabolism of methidathion to CO2 and nonextractable
      material.  The oxygen analog has not been detected in soil.  Field and
      laboratory studies have demonstrated leaching distance to be a direct
      function of organic matter content with essentially no leaching
      observed below the six-inch depth even in low organic matter soils.
      Hydrolysis and photolysis are not significant degradation mechanisms in
      the soil environment; however, aqueous hydrolysis studies reveal a
      half-life of about 30 days.

           As the compound is metabolized and degradation products bound to
      soil, water contamination would occur only under conditions favoring
      runoff of treated soil particles or by accidental spillage.  Fish
      studies have demonstrated minimal bioaccumulation with rapid
      dissipation of residues when removed from exposure conditions (24d).

           Observations have been made in alfalfa, citrus, and cotton plots
      treated with Supracide 2E that show a resurgence of beneficial
      arthropod populations associated with pests of those crops.  Some of
      these observations have been associated with lower use rates (24d).

      Approximate Residual Period:  1-3 weeks on plants (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
      Control Center.

      FREQUENT SYMPTOMS AND SIGNS OF POISONING BY ORGANOPHOSPHATE PESTICIDES

           Symptoms of acute poisoning develop during exposure or within 12
      hours (usually within four hours) of contact.  HEADACHE, DIZZINESS,
      WEAKNESS, INCOORDINATION, MUSCLE TWITCHING, TREMOR, NAUSEA, ABDOMINAL
      CRAMPS, DIARRHEA, and SWEATING are common early symptoms.  Blurred or
      dark vision, confusion, tightness in the chest, wheezing, productive
      cough, and PULMONARY EDEMA may occur.  Incontinence, unconsciousness
      and convulsions indicate very severe poisoning.  SLOW HEARTBEAT,
      salivation, and tearing are common.  TOXIC PSYCHOSIS, with manic or
      bizarre behavior, has led to misdiagnosis of acute alcoholism.  Slowing
      of the heartbeat may rarely progress to compete sinus arrest.
      RESPIRATORY DEPRESSION may be fatal.  Continuing daily absorption of
      organophosphate at intermediate dosage may cause an INFLUENZA-LIKE
      ILLNESS characterized by weakness, anorexia, and malaise (25).

           SKIN CONTACT:  Bathe and shampoo victim with soap and water if
      there is any chance that skin and hair are contaminated (25).

           INGESTION:  If victim is alert and respiration is not
      depressed, give Syrup of Ipecac, followed by 1-2 glasses of water to
      induce vomiting.  Adults (12 years and over): 30 ml; children under 12
      years: 15 ml (25).

      NOTES TO PHYSICIAN:

      Administer ATROPINE SULFATE intravenously, or intramuscularly, if IV
      injection is not possible.
      In MODERATELY SEVERE poisoning:  Adult dosage:  0.4-2.0 mg repeated
      every 15 minutes until atropinization is achieved:  tachycardia (pulse
      of 140 per minute), flushing, dry mouth, dilated pupils.  Maintain
      atropinization by repeated doses for 2-12 hours or longer depending on
      severity of poisoning.
      Dosage for children under 12 years:  0.05 mg/kg body weight, repeated
      every 15 minutes until atropinization is achieved.  Maintain
      atropinization with repeated dosage of 0.02-0.05 mg/kg.
      SEVERELY POISONED individuals may exhibit remarkable tolerance to
      atropine; two or more times the dosages suggested above may be needed.
      Administer PRALIDOXIME (Protopam (TM)-Ayerst, 2-PAM) in cases of severe
      poisoning in which respiratory depression, muscle weakness and
      twitchings are severe.
      Adult dosage:  1.0 gm intravenously at no more than 0.5 gm per minute.
      Child's dose (under 12 years):  20-50 mg/kg (depending on severity of
      poisoning) intravenously, injecting no more than half the total dose
      per minute.
      Dosage of pralidoxime may be repeated in 1-2 hours, then at 10-12 hour
      intervals if needed.  In very severe poisonings, dosage rates may be
      doubled (25).


                        VI.  FIRE AND EXPLOSION INFORMATION

           To be developed.


                                VII.  COMPATIBILITY

           On tobacco do not apply in mixture with other pesticides (1).
      Mixing with alkaline materials may reduce the effectiveness.  Compatible
      with a number of other pesticides (8a).


                            VIII.  PROTECTIVE MEASURES

      STORAGE AND HANDLING:  Supracide 2E shelf-life of at least 3-5 years
      when stored in a dry place and minimum storage temperatures (above 32 F)
      are observed (56).


                       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

       1.  Harding, W.C.  1979.  Pesticide profiles, part one: insecticides
               and miticides.  Univ. Maryland, Coop. Ext. Serv. Bull. 267.
               30 pp.

       8a. Thomson, W. T.  1976.  Agricultural chemicals - book 1:
               insecticides, acaricides, and ovicides.  Revised ed.  Thomson
               Publ., Indianapolis, IN.  232 pp.

      24d. Ciba-Geigy Corporation, Agricultural Division.  1979.  Technical
               bulletin:  Supracide insecticide.  Greensboro, NC.

      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.

      62.  The Pesticide Manual:  A World Compendium, 7th ed.  1983.  C.R.
               Worthing, ed.  The British Crop Protection Council, Croydon,
               England.  695 pp.

      4/9/85