pyrazon (Pyramin) Herbicide Profile 2/85
CHEMICAL NAME: 5-amino-4-chloro-2-phenyl-3-(2H)-pyridazinone (56)
TRADE NAME(S): Pyramin (56)
FORMULATION(S): Wettable powder (56)
BASIC PRODUCER(S): BASF Wyandotte Corp.
Agricultural Chemicals Div.
100 Cherry Hill Rd.
Parsippany, NJ 07054
STATUS: General use
PRINCIPAL USES: For preemergence and early postemergence weed
control. Applied at planting time or shortly after planting time of
sugar beets, red beets and fodder beets (56).
APPLICATION METHOD(S): Generally preemergence, broadcast or early
postemergence, banded. In irrigated western regions banded preemergence
application with sprinkler irrigation or banded, shallow, preplant soil
incorporation with furrow irrigation is recommended. Pyrazon can be
mixed with other herbicides including phenmedipham and desmedipham for
control of additional weeds in sugarbeets (58).
Controls annual broadleaf weeds in sugarbeets and red beets.
Control of annual grasses is not consistently obtained (58).
Important Weeds Controlled: Lambsquarters, mustards, ragweed, purslane,
smartweed, pigweed, henbit, shepherd's purse, nightshade, groundsel,
dock, spurge, chickweed, wild radish and others (8b).
Weeds lose much of their susceptibility by the time they have
four true leaves. Perennial weeds are not controlled. Preemergence
applications are not effective under furrow irrigation unless
incorporated. Moisture is required to activate this material. Weed
control can be expected for 4-8 weeks. Somewhat ineffective on grasses.
A light incorporation (1-2 inches) gives better results than a deep
one (4-5 inches). Use on soils where the organic matter is higher than
5%, will result in erratic weed control under dry weather conditions
II. PHYSICAL PROPERTIES
MOLECULAR FORMULA: C10 H8 C1 N3 O (62)
MOLECULAR WEIGHT: 221.6 (62)
PHYSICAL STATE: Tan to brown powder (pure compound) (58);
solid, dark brown (technical a.i.) (56).
ODOR: Approx. odorless (technical a.i.) (56); odorless
when pure (58).
MELTING POINT: 207 C (with decomp.) (pure compound) (58)
VAPOR PRESSURE: 0.074 mmHg at 40 C (pure compound) (58)
SOLUBILITY: 0.04 g/100 g water at 20 C (pure compound) (58)
III. HEALTH HAZARD INFORMATION
OSHA STANDARD: NA
NIOSH RECOMMENDED LIMIT: NA
ACGIH RECOMMENDED LIMIT: NA
A. ACUTE TOXICITY
DERMAL: No toxicity to skin observed (58).
ORAL: LD50 = 3030 mg/kg (rat) (form. prod.) (56)
LD50 = 3600 mg/kg (rat), 3000 mg/kg (mouse), 1250
mg/kg (rabbit) (58).
LD50 = 2424 mg a.i. (as w.p.)/kg (rat) (62).
B. SUBACUTE AND CHRONIC TOXICITY:
In 2-year feeding trials rats receiving 300 mg/kg diet suffered no
detectable toxic effect (62).
Rats - 15 weeks: 5000 ppm of total diet showed no histological or
pathological changes over control.
In 2-year studies, rats and dogs were fed diets containing 300 and
1500 ppm, respectively, of Pyramin without any noticeable effects (58).
Application to backs and ears of white rabbits (20-hr) caused slight
temporary erythema (62).
IV. ENVIRONMENTAL CONSIDERATIONS
Not significantly hazardous to fish (bluegill and fathead minnows,
LC50 approximately 40 ppm) (58).
Behavior In or On Soils
1. Adsorption and leaching characteristics in basic soil types:
Preemergence use is not recommended on soils classified as sands
or loamy sands because of leaching and possible crop injury.
Adsorption on soils containing greater than 5% organic matter
precludes adequate weed control.
2. Microbial breakdown: Depending upon soil temperature and moisture
in the treated zone, the microbial breakdown can be moderately
rapid. The principal degradation product is dephenylated pyrazon
which is not significantly herbicidal.
3. Loss from photodecomposition and/or volatilization: Negligible.
4. Resultant average persistence at recommended rates: 4 to 8 weeks,
depending upon soil moisture and temperature (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
SYMPTOMS OF POISONING: None noted to date for humans (58).
SKIN CONTACT: Remove contaminated clothing and wash skin with
soap and water. Consult a physician if irritation persists (56).
INGESTION: Induce vomiting and consult a physician (56).
EYE CONTACT: Flush eyes immediately with water for at least 15
VI. FIRE AND EXPLOSION INFORMATION
Dry powder, nonflammable (58).
Generally compatible with other sugarbeet herbicides with which it
is likely to be used. As a general precaution when tank-mixing with
liquid formulations a good suspension of pyrazon should be obtained
before adding the liquid herbicides. Noncorrosive (58).
VIII. PROTECTIVE MEASURES
STORAGE AND HANDLING: Avoid contact with skin, eyes and clothing.
Harmful if swallowed (58).
IX. PROCEDURES FOR SPILLS AND LEAKS
IN CASE OF EMERGENCY, CALL, DAY OR NIGHT
PESTICIDE TEAM SAFETY NETWORK/CHEMTREC
X. LITERATURE CITED
8b. Thomson, W.T. 1981. Agricultural chemicals - book 2:
herbicides. Revised ed. Thomson Publications, Fresno, CA.
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.