maleic hydrazide (Royal MH-30) Herbicide Profile 3/85
CHEMICAL NAME: 1,2-dihydro-3,6-pyridazinedione (58)
TRADE NAME(S): Royal MH-30, Sprout-Stop, Retard, Fair Plus, etc.
FORMULATION(S): Water-soluble liquids of the diethanolamine salt or
the potassium salt (56).
TYPE: Pyridazinone herbicide
BASIC PRODUCER(S): Drexel Chemical Co. Fairmont Chemical Co., Inc.
2487 Pennsylvania St. 117 Blanchard St.
P.O. Box 9306 Newark, NJ 07105
Memphis, TN 38109
Div. of Uniroyal, Inc.
Naugatuck, CT 06770
STATUS: General use. RPAR issued 10/28/77, criteria possibly
met or exceeded: oncogenicity, mutagenicity, reproductive
effects. Returned to the Registration Process 6/28/82. Additional
reproductive and mutagenicity studies have been performed on K-MH as
required. Registrants decided not to perform similar tests on DEA-MH
and thus DEA-MH was suspended 11/81 (22).
PRINCIPAL USES: Primary uses include sucker control on tobacco,
sprout inhibition in stored onions and potatoes, frost protection in
citrus and turf and roadside maintenance. Maleic hydrazide has
herbicidal activity on quackgrass, wild onions, and wild garlic (58).
Maleic hydrozide is recommended for the temporary growth
inhibition of various trees, shrubs and grasses (56).
APPLICATION METHOD(S): Used as a over-the-top foliar spray. Dosage
and stage of plant development are critical factors (58).
To be developed.
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C4 H4 N2 O2 (58)
MOLECULAR WEIGHT: 112.1 (58)
PHYSICAL STATE: White solid (pure compound) (58); colorless
crystalline solid (dry technical grade, >99% pure)
ODOR: Odorless (pure compound) (58)
MELTING POINT: 300 C (pure compound) (58); 292-298 C (technical
DECOMPOSITION TEMPERATURE: About 260 C (pure compound) (58)
BOILING POINT: Does not boil (pure compound) (58)
VAPOR PRESSURE: Essentially zero (pure compound) (58)
SOLUBILITY: 6000 ppm at 25 C (pure compound) (58)
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: None established
NIOSH RECOMMENDED LIMIT: None established
ACGIH RECOMMENDED LIMIT: None established
A. ACUTE TOXICITY
DERMAL: LD50 = >2000 mg/kg (rabbit) (62).
LD50 = >8000 mg/kg (rabbit, Royal MH) (58).
Moderate skin irritation for rabbits (58).
ORAL: LD50 (rat) = 6950 mg/kg (sodium salt of MH); 3900
mg/kg (MH-30); 14145 mg/kg (Royal MH); >5000 mg/kg
(technical MH) (58).
INHALATION: LC50 = >20 mg/l air (rat) (62).
LC50 = >200 mg/l air (rat, Royal MH) (58).
EYES: Severe eye irritation for rabbits (58).
B. SUBACUTE AND CHRONIC TOXICITY:
Two-year feeding studies of rats at the 6.0% level of sodium salt
of MH (equivalent to about 5% MH acid equivalent) showed no toxicity
In 2-yr. feeding trials, including a 3-generation reproduction
study, rats receiving 50,000 mg sodium salt/kg diet showed no
ill-effect. There was no oncogenic effect by the potassium salt in
mice; in a 1-yr. trial on dogs with 20,000 mg sodium salt/kg diet mild
reversible effects were noted. Maleic hydrazide gave negative results
in mutagenicity tests (62).
IV. ENVIRONMENTAL CONSIDERATIONS
Behavior In Or On Soils
1. Microbial breakdown: Rapidly broken down by soil microorganisms.
2. Average persistence at recommended rates: No residual effect (58).
No mortality at 10.0 ppm to bluegills and fatheads (58).
LC50 (96-hr) is: for bluegill 1608 mg/l; for rainbow trout 1435
mg/l; for Daphnia spp. 107 mg/l (62).
LD50 = >10,000 m/kg (mallard duck, bobwhite quail) (62).
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 substitute for a more exhaustive
review of the literature nor for the judgement of a physician or other
If poisoning is suspected, do not wait for symptoms to develop.
Contact a physician, the nearest hospital, or the nearest Poison
KNOWN OR SUSPECTED ADVERSE EFFECTS: Slightly irritating (25). No
symptoms of poisoning encountered in field usage (58).
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
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
EYE CONTACT: FLUSH contaminated EYES with copious amounts of
fresh water for 15 minutes (25).
NOTES TO PHYSICIAN:
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
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
(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.
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.
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
Not flammable, a water solution (58).
If in the presence of a strong acid, the MH acid may precipitate.
Do not use concentrate through brass nozzles as the amine content may
cause erosion (58).
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: The formulation has been held as long as 10
years with no breakdown. Light and temperature stability are very good
PROTECTIVE CLOTHING: No protective clothing required (58).
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
X. LITERATURE CITED
22. U.S. Environmental Protection Agency, Office of Pesticide
Programs. 1983. June 1983 status report on rebuttable
presumption against registration (RPAR) or special review
process, registration standards and the data call in
programs. Washington, DC. 45 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.
62. The Pesticide Manual: A World Compendium, 7th ed. 1983. C.R.
Worthing, ed. The British Crop Protection Council, Croydon,
England. 695 pp.
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