methidathion (Supracide) Chemical Profile 4/85
CHEMICAL NAME: O,O-dimethyl phosphorodithioate, S-ester with
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).
Pests Effectively Controlled:
Alfalfa Deciduous Fruit Nursery Stock
_______ _______________ _____________
alfalfa weevil peach twig borer pine needle scale
aphids San Jose scale
leafhoppers green peach aphid
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
Pome and Drupe Fruit
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
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)
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
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
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
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
VI. FIRE AND EXPLOSION INFORMATION
To be developed.
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
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.
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.