Description
Clopyralid is an herbicide that selectively inhibits the growth of the broadleaf weed
L. palustris over a panel of 17 New Zealand native non-broadleaf plant species when applied at a concentration of 1.5 mg/L. It does not inhibit growth of human pluripotent stem cells (IC
50 = >100 μM) or decrease nuclear translocation of the transcription factor SOX17, a marker of teratogenic risk.
In vivo, clopyralid induces brain defects in rabbits, but not rats, when administered at a dose of 250 mg/kg.
Chemical Properties
White Crystalline Solid
Chemical Properties
Odorless and colorless crystalline solid. Odorless. Available as a soluble concentrate that is usually mixed with water. Combustible
Uses
Systemic post-emergence herbicide for use in food crops and mesquite.
Definition
ChEBI: An organochlorine pesticide having a 3,6-dichlorinated picolinic acid structure.
Agricultural Uses
Herbicide: Clopyralid is used to control annual and perennial
broadleaf weeds on rangeland, pastures, turf and lawns,
rights-of-way and a few agricultural products such as
sugar beets, oats, barley, mint and wheat.
Trade name
ACCENT®; CONFRONT®; CURTAIL®;
CURTAIL M®; DOWCO®-290; HORNET®;
LONTREL®; LONTREL® 3; LONTRIL® F;
LONTRIL® T; MATRIGON®; MILLENNIUM®;
NAF®-280; PARADIGM®; RECLAIM®; REDEEM®;
RIVERDALE®; SCORPION®; STINGER®;
TRANSLINE®; WIDEMATCH®; XRM-3972®
Pharmacology
Clopyralid is systemic herbicides that is actively absorbed by foliage
and, is also readily
absorbed through root tissues. Once absorbed, it is translocated, primarily in the phloem,
throughout the entire plant. At normal field doses, this
herbicide controls many broadleaf species and are selective
in pasturelands and most grass crops. The exact weed
spectrum and use is specific to the compound.
Potential Exposure
Clopyralid is a pyralid herbicide used to control annual and perennial broadleaf weeds on rangeland, pastures, turf, and lawns, rights-of-way and a few agricultural products such as sugarbeets, oats, barley, mint, and wheat.
Environmental Fate
Clopyralid is a relatively strong
acid and water soluble, making it susceptible to leaching.
Most studies, however, indicate that it is metabolized
relatively quickly by soilmicrobes, significantly decreasing
the amount of clopyralid that is available for this process.
Clopyralid is dissociated in soil because of its low pKa, and
thus, its adsorption to most soils is weak and governed
by the anion exchange capacity. Soils with relatively
large anion exchange capacities will bind relatively large
quantities of clopyralid,making it biologically unavailable.
Clopyralid is not volatile.
Metabolism
Chemical. Clopyralid is stable to hydrolytic decomposition
in acidic conditions becoming unstable above pH 5.
It does not undergo significant photolytic degradation.
Clopyralid decomposes above its melting point.
Plant. Hall and Vanden Born (29) showed that clopyralid
underwent substantial metabolism in tolerant Brasica
napus; i.e., 70% of applied clopyralid was metabolized
144 hours after application. Themetabolites were not fully
characterized. Relatively little metabolism is thought to
occur in susceptible plants.
Soil. Clopyralid is readily degraded by soil microbes,
e.g., the field dissipation DT
50 ranges from 8 to
66 days. The major metabolic pathway in soil microbes
is decarboxylation.
Shipping
UN3077 Environmentally Hazardous substances, solid, n.o.s., Hazard class: 9; Labels: 9-Miscellaneous hazardous material, Technical Name Required
Toxicity evaluation
Mammalian Toxicity. Limited studies have been conducted,
but, from what data exist, it appears that clopyralid
is quickly excreted, unmodified, in the urine of
animals. The acute oral LD
50 of clopyralid in male and
female rat is 3738 mg/kg and 2775 mg/kg, respectively.
Weed Resistance/Modified Crop Tolerance. Fuerst et al.
(48) reported clopyralid resistance in yellow starthistle
(Centaurea solstitialis). No crops with modified tolerance
toward clopyralid are currently in production.
Incompatibilities
May react violently with strong oxidizers, bromine, 90% hydrogen peroxide, phosphorus trichloride, silver powders, or dust. Incompatible with silver compounds. Mixture with some silver compounds forms explosive salts of silver oxalate. Keep away from oxidizers, sulfuric acid, caustics, ammonia, aliphatic amines, alkanolamines, isocyanates, alkylene oxides, epichlorohydrin. Solutions are strong acids; corrosive to aluminum, iron, and tin. Compounds of the carboxyl group react with all bases, both inorganic and organic (i.e., amines) releasing substantial heat, water, and a salt that may be harmful. Incompatible with arsenic compounds (releases hydrogen cyanide gas), diazo compounds, dithiocarbamates, isocyanates, mercaptans, nitrides, sulfides (releasing heat, toxic, and possibly flammable gases), thiosulfates, and dithionites (releasing hydrogen sulfate and oxides of sulfur).
Waste Disposal
Containers must be disposed of properly by following package label directions or by contacting your local or federal environmental control agency, or by contacting your regional EPA office. Dissolve or mix the material with a combustible solvent and burn in a chemical incinerator equipped with an Clopyralid 877 afterburner and scrubber. In accordance with 40CFR165, follow recommendations for the disposal of pesticides and pesticide containers.
