methamidophos (Monitor) Chemical Profile 4/95
CHEMICAL NAME: O,S-Dimethyl phosphoramidothioate (56)
DEC INGRED. CODE:
TRADE NAME(S): Monitor (1)
FORMULATION(S): 4 lb/gal liquid concentrate, emulsifiable
concentrate, wettable powder, granules (1).
Liquid concentrate; 40% and 60% w/v (56).
TYPE: Organophosphate insecticide
BASIC PRODUCER(S): Chevron Chemical Co. Mobay Chemical Corp.
Ortho Agr. Chemicals Div. Agr. Chemicals Div.
575 Market St. P. O. Box 4913
P.O. Box 3744 Kansas City, MO 64120
San Francisco, CA 94105
STATUS: Restricted use
PRINCIPAL USES: Controls certain lepidopterous larvae on vegetables
(especially crucifers) and field crops. Some local foliar systemic
Controls certain lepidopterous larvae (certain cutworms, loopers),
aphids, mites, and whiteflies. Tolerances granted on broccoli, Brussels
sprouts, cabbage, cauliflower, lettuce, cotton seed, potatoes, tomatoes,
cucumbers, eggplants, peppers, and melons. Also for control of aphids in
potatoes and peaches (56).
Field trials have shown outstanding performance in controlling the
insect pest complex (including the resistant cabbage looper
(Trichoplusia ni)), infesting cole crops. It is very effective against
green peach aphid (Myzus persicae) and many other species of aphids.
Monitor effectively controls the major pests of the potato including
aphids, potato leafhopper, Colorado potato beetle, flea beetle, potato
tuberworm and the cabbage looper (17c).
Important Pests Controlled: Aphids, flea beetles, worms, white flies,
cabbage lopper, thrips, cutworms, Colorado potato beetle, potato
tuberworms, armyworms, mites, leafhoppers and many others (8a).
Besides being a contact and stomach poison it possesses systemic
activity. Good residual effectiveness (8a).
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C2 H8 NO2 P S (62)
MOLECULAR WEIGHT: 141.1 (62)
PHYSICAL STATE: Solid (pure compound) (62)
MELTING POINT: 44.5 C (pure compound) (62)
VAPOR PRESSURE: 40 mPa at 30 C (pure compound) (62)
SOLUBILITY: >2 kg/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 = 50-110 mg/kg (male rat) (62)
LD50 = 118 mg/kg (rabbit, 75% tech.) (56)
ORAL: LD50 = 30 mg/kg (rats and mice); 30-50 mg/kg (guinea-
pig); 10-30 mg/kg (rabbit); 25 mg/kg (hen) (62)
LD50 = 18-21 mg/kg (rat, 75% tech.) (56)
B. SUBACUTE AND CHRONIC TOXICITY:
In 2-yr feeding trials: dogs receiving 0.75 mg/kg daily showed
no significant abnormalities; rats receiving 10 mg/kg diet showed no
IV. ENVIRONMENTAL CONSIDERATIONS
Moderately hazardous to birds, fish and beneficial insects.
Hazardous to honey bees. Biological magnification unlikely. Some
injury reported on apples (1).
The acute oral LD50 for bobwhite quail is 57.5 mg/kg (62).
The LC50 (96 hr.) is: for trout 51 mg/l; for guppies 46 mg/l (62).
Approximate Residual Period: 1-2 weeks on plants. Possibly longer as
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, reproductive
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 complete 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
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.
Compatible with most fungicides and insecticides (1). Slightly
corrosive to mild steel and copper alloys. Do not mix with alkaline
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Fatal if swallowed, inhaled, or absorbed through
skin. Do not get in eyes, on skin, or clothing. Do not breathe dust,
keep container closed. Use with adequate ventilation. Wash thoroughly
after handling. Do not contaminate food or feed products. Do not drink
any alcoholic beverages before or during spraying since alcohol promotes
absorption of organic phosphates (56).
PROTECTIVE CLOTHING: Personnel must wear full protective equipment at
all times. This includes: Neoprene-coated gloves, rubber workshoes or
over-shoes, respirator or mask approved for toxic dust and organic
vapors, overalls or rubber suit (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.
17c. Chevron Chemical Company, Ortho Division. 1973. Experimental
data sheet: Monitor insecticide. Moorestown, 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.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.