Clopyralid

Clopyralid	Last updated: 28/02/2025
(Also known as: clopyralid-olamine; Dowco 290; clopyralid acid; 3,6-dichloropicolinic acid; DCP)

SUMMARY

A post-emergence herbicide for control of broadleaved weeds. It has a high aqueous solubility, is volatile and, based on its chemical properties, there is a high risk of it leaching to groundwater. It can be persistent in both soil and water systems depending upon conditions. It has a low mammalian toxicity and is not expected to bioaccumulate. It is an irritant. It is moderately toxic to birds, fish, aquatic invertebrates, honeybees and earthworms. It has a low toxicity to aquatic plants and algae.

Data alerts

The following alerts are based on the data in the tables below. An absence of an alert does not imply the substance has no implications for human health, biodiversity or the environment but just that we do not have the data to form a judgement.

Environmental fate	Ecotoxicity	Human health
Environmental fate High alert: GUS: High leachability; Drainflow: Very mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Bees acute contact ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health Moderate alert: Reproduction/development effects

GENERAL INFORMATION

Description

A herbicide for a post-emergence control of many broadleaved weeds in a range of crops

Example pests controlled

Broadleaved weeds generally; Capeweed; Volunteer peas; Thistles; Prickly lettuce; Knapweed; Volunteer vetch; Cape ivy

Example applications

Cereals including wheat, barley, oats, triticale; Turf; Ornamentals; Non-cropped and fallow land; Industrial situations

Efficacy & activity

Research supports the effectiveness of clopyralid to control a wide range of broadleaved weeds

Availability status

Current

Introduction & key dates

1977, registered France

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

30/04/2029

GB LERAP status

Check label - may vary with formulation

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Finland/Poland

Date EC 1107/2009 inclusion expires

30/09/2036

EU Candidate for substitution (CfS)

Listed in EU database

Yes

Approved for use (✓) under EC 1107/2009 in the following EU Member States

ATAustria	BEBelgium	BGBulgaria	CYCyprus	CZCzech Republic	DEGermany	DKDenmark	EEEstonia	ELGreece
✓	✓	✓	✓	✓	✓	✓	✓	✓
ESSpain	FIFinland	FRFrance	HRCroatia	HUHungary	IEIreland	ITItaly	LTLithuania	LULuxembourg
✓	✓	✓	✓	✓	✓	✓	✓	✓
LVLatvia	MTMalta	NLNetherlands	PLPoland	PTPortugal	RORomania	SESweden	SISlovenia	SKSlovakia
✓		✓	✓	✓	✓	✓	✓	✓

Approved for use (✓) under EC 1107/2009 by Mutual Recognition of Authorisation and/or national regulations in the following EEA countries

ISIceland	NONorway
	✓

Additional information

Also used in

Australia; USA; Morocco

Chemical structure

Isomerism

None

Chemical formula

C₆H₃Cl₂NO₂

Canonical SMILES

C1=CC(=NC(=C1Cl)C(=O)O)Cl

Isomeric SMILES

International Chemical Identifier key (InChIKey)

HUBANNPOLNYSAD-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C6H3Cl2NO2/c7-3-1-2-4(8)9-5(3)6(10)11/h1-2H,(H,10,11)

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Pyridine herbicide; Picolinic acid herbicide

Minimum active substance purity

950 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Selective, systemic, absorbed through leaves and roots. Synthetic auxin.

CAS RN

1702-17-6

EC number

216-935-4

CIPAC number

455

US EPA chemical code

117401

PubChem CID

15553

CLP index number

607-231-00-1

Molecular mass

192.0

PIN (Preferred Identification Name)

3,6-dichloropyridine-2-carboxylic acid

IUPAC name

3,6-dichloropyridine-2-carboxylic acid

CAS name

3,6-dichloro-2-pyridinecarboxylic acid

Other status information

PAN Listed as Highly Hazardous Chemical; Potential groundwater contaminant

Relevant Environmental Water Quality Standards

Herbicide Resistance Class (HRAC MoA class)

Herbicide Resistance Class (WSSA MoA class)

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Not applicable

Examples of recorded resistance

Physical state

Cream to white coloured crystals

Related substances & organisms

clopyralid-dimethylammonium

clopyralid-methyl

clopyralid-olamine

clopyralid-tripromine

Formulations

Property

Value

Example manufacturers & suppliers of products using this active now or historically

AgriGuard
Dow AgroSciences
Teliton

Example products using this active

Esteem
Galera
Grazon 90
Stinger
Lontrel
Dowco 290
Agvalue Clopyralid Technical
Brazen SF Herbicide
Arianne S

Formulation and application details

Usually supplied as a soluble concentrate, wettable powder or emulsifiable concentrate

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

Solubility - In water at 20 °C (mg l⁻¹)

7850

High

Solubility - In organic solvents at 20 °C (mg l⁻¹)

250000

Acetone

102000

Ethyl acetate

4600

Xylene

6000

n-Hexane

Melting point (°C)

149.6

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

164

Flashpoint (°C)

Octanol-water partition coefficient at pH 7, 20 °C

2.34 X 10^-03

Calculated

Log P

-2.63

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.76

Dissociation constant pKa) at 25 °C

2.01

Strong acid

Vapour pressure at 20 °C (mPa)

1.36

Low volatility. If applied directly to plants or soil, drift is a concern & mitigation is advisable

Henry's law constant at 25 °C (Pa m³ mol⁻¹)

1.80 X 10^-11

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

Maximum UV-vis absorption L mol⁻¹ cm⁻¹

Neutral solution: Maxima at 220nm, 280nm : 22100nm, 9200nm & 4790nm
Acidic solution: Maxima at 202nm, 225nm, 281nm : 16200nm, 8890nm & 3800nm
Basic solution: Maxima at 220nm, 279nm : 9300nm, 5030nm

Surface tension (mN m⁻¹)

71.5

at 20 °C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Not readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

23.2

Non-persistent

DT₅₀ (lab at 20 °C)

23.2

Non-persistent

DT₅₀ (field)

8.2

Non-persistent

DT₉₀ (lab at 20 °C)

82.6

Moderately persistent

DT₉₀ (field)

49.5

DT₅₀ modelling endpoint

23.7

representative of field studies

Note

EU 2017 dossier lab studies DT₅₀ range 4.9-64.6 days, DT₉₀ range 16.2-214.6 days, Soils=10; field studies DT₅₀ range 2.0-13.5 days, DT₉₀ range 12.1-78.7 days; Other sources: DT₅₀ 40 days (R3)

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

5.4

Note

Published literature RL₅₀ range 4.3-6.7 days, 3 field crops, various matrices, n=3

Aqueous photolysis DT₅₀ (days) at pH 7

Value

271

Stable

Note

Not significant degradation route

Aqueous hydrolysis DT₅₀ (days) at 20 °C and pH 7

Value

Stable

Note

Stable pH 4 to pH 9, 50 °C

Water-sediment DT₅₀ (days)

Water phase only DT₅₀ (days)

148

Stable

Sediment phase only DT₅₀ (days)

Air degradation

As this parameter is not normally measured directly, a surrogate measure is used: ‘Photochemical oxidative DT₅₀’. Where data is available, this can be found in the Fate Indices section below.

Decay in stored produce DT₅₀

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d (mL g⁻¹)

0.071

Very mobile

K_oc (mL g⁻¹)

5.0

Notes and range

EU dossier K_d range 0.032-0.151, K_oc range 3.43-7.34 mL g⁻¹, Soils=5

Freundlich

K_f (mL g⁻¹)

K_foc (mL g⁻¹)

¹/_n

Notes and range

pH sensitivity

Limited evidence of decreasing adsorption with increasing pH

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

3.02

Calculated

High leachability

SCI-GROW groundwater index (μg l⁻¹) for a 1 kg ha⁻¹ or 1 l ha⁻¹ application rate

Value

4.30 X 10^-02

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Very mobile

Calculated

Photochemical oxidative DT₅₀ (hrs) as indicator of long-range air transport risk

468

Calculated using the Atkinson method

Substance of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

Lepomis macrochirus

Low potential

CT₅₀ (days)

0.1

Known metabolites

None

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

> 15

Rat 2 yr

High

(ppm diet)

> 150

Mammals - Chronic 21d NOAEL (mg kg⁻¹ bw d⁻¹)

> 1500

Unknown species Reproductive NOAEL

Low

Birds - Acute LD₅₀ (mg kg⁻¹)

1465

Anas platyrhynchos

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 1033 mg kg bw⁻¹ day⁻¹

Colinus virginianus

Birds - Chronic 21d NOEL (mg kg⁻¹ bw d⁻¹)

118

Anas platyrhynchos NOEC

Moderate

Earthworms - Acute 14 day LC₅₀ (mg kg⁻¹)

> 1000

Eisenia foetida

Low

Earthworms - Chronic NOEC, reproduction (mg kg⁻¹)

>= 1.97

Eisenia foetida

Moderate

Soil micro-organisms

Nitrogen mineralisation: No significant adverse effect
Carbon mineralisation: No significant adverse effect

Dose: 5 x field rate

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

> 50

Folsomia candida

Non-target plants

Honeybees (Apis spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 98.1

Apis mellifera

Moderate

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

> 100

Apis mellifera

Low

Unknown mode acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Chronic

Notes

Bumblebees (Bombus spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Mason bees (Osmia spp.)

Contact acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Oral acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg bee⁻¹)

Other bee species (1)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Other bee species (2)

Acute LD₅₀ (worst case from 24, 48 and 72 hour values - μg insect⁻¹)

Mode of exposure

Beneficial insects (Ladybirds)

Beneficial insects (Lacewings) as Mortality LR₅₀ mL/ha

2000

Chrysoperla carnea

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ mL/ha

2000

Aphidius rhopalosiphi

Beneficial insects (Predatory mites) as Mortality LR₅₀ mL/ha

2000

Typhlodromus pyri

Beneficial insects (Ground beetles)

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Temperate Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

> 99.9

Oncorhynchus mykiss

Moderate

Temperate Freshwater Fish - Chronic 21 day NOEC (mg l⁻¹)

10.8

Pimephales promelas

Low

Tropical Freshwater Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

Temperate Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

> 99

Daphnia magna

Moderate

Temperate Freshwater Aquatic invertebrates - Chronic 21 day NOEC (mg l⁻¹)

Daphnia magna

Low

Tropical Freshwater Aquatic invertebrates - Acute 48 hour EC₅₀ (mg l⁻¹)

Aquatic crustaceans - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Acute 96 hour LC₅₀ (mg l⁻¹)

Sediment dwelling organisms - Chronic 28 day NOEC, static, water (mg l⁻¹)

50.0

Chironomus riparius

Low

Sediment dwelling organisms - Chronic 28 day NOEC, sediment (mg kg⁻¹)

Aquatic plants (free-floating, growth) - Acute 7 day EC₅₀, biomass (mg l⁻¹)

Lemna gibba

Low

Aquatic plants (rooted, growth) - Acute 14 day EC₅₀, biomass (mg l⁻¹)

> 3.0

Myriophyllum spicatum

Moderate

Algae - Acute 72 hour EC₅₀, growth (mg l⁻¹)

30.5

Raphidocelis subcapitata

Low

Algae - Chronic 96 hour NOEC, growth (mg l⁻¹)

Unknown species

Low

Mesocosm study data

NOEAEC mg l⁻¹

Marine bivalves

HUMAN HEALTH AND PROTECTION

General

Property

Value

Source; quality score; and other information

Interpretation

Threshold of Toxicological Concern (Cramer Class)

High (class III)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 5000

Rat

Low

Mammals - Dermal LD₅₀ (mg kg⁻¹ body weight)

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 1.0

Rat (nose only)

Other Mammal toxicity endpoints

ADI - Acceptable Daily Intake (mg kg⁻¹ bw day⁻¹)

0.15

Rat SF=100

ARfD - Acute Reference Dose (mg kg⁻¹ bw day⁻¹)

0.17

AAOEL - Acute Acceptable Operator Exposure Level (mg kg⁻¹ bw day⁻¹)

0.17

AOEL - Acceptable Operator Exposure Level - Systemic (mg kg⁻¹ bw day⁻¹)

0.15

Dermal penetration studies (%)

25-75

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

Minimal risk of dietary exposure

Occupational

Risk of exposure acceptable under label recommendations for use for personal protection clothing and equipment

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

Mammalian dose elimination route and rate

Rapid and extensive elimination as parent material mainly via urine

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

No data found

Eye irritant

Phototoxicant

No data found

General human health issues

Possible liver and kidney toxicant

Handling issues

Property

Value and interpretation

General

Prevent release of dust
Not explosive or oxidising
Not expected to auto-ignite; Not highly flammable
Corrosive

CLP classification 2013

Health: H318

WHO Classification

III (Slightly hazardous)

UN Number

UN3077

Waste disposal & packaging

Packaging Group III (minor danger)

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

clopyralid

French

clopyralid

German

Clopyralid

Danish

clopyralid

Italian

clopiralid

Spanish

clopiralida

Greek

clopyralid

Polish

chlopyralid

Swedish

klopyralid

Hungarian

klopiralid

Dutch

clopyralid

Norwegian

klopyralid

Record last updated:	28/02/2025
Contact:	aeru@herts.ac.uk
Please cite as:	Lewis, K.A., Tzilivakis, J., Warner, D. and Green, A. (2016) An international database for pesticide risk assessments and management. Human and Ecological Risk Assessment: An International Journal, 22(4), 1050-1064. DOI: 10.1080/10807039.2015.1133242