Clethodim (Ref: RE 45601)

Clethodim (Ref: RE 45601)	Last updated: 22/08/2025
(Also known as: cletodime)

SUMMARY

Clethodim is a herbicide that is used to control annual and perennial grasses. It is highly soluble in water and has a low volatility. It tends not to be persistent in soil or aquatic systems. It is moderately toxic to birds, fish, aquatic plants, honeybees and earthworms but is less toxic to aquatic invertebrates and algae. Clethodim is moderately toxic to mammals and whilst it is a skin irritant no evidence of it causing more serious health effects have been found.

Hazard 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. These hazard alerts do not take account of usage patterns or exposure, thus do not represent risk.

Environmental fate	Ecotoxicity	Human health
Environmental fate High alert: Drainflow: Mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate; Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate	Human health High alert: Reproduction/development effects

GENERAL INFORMATION

Description

A herbicide used to control annual and perennial grasses for use on sugarbeet and other crops

Example pests controlled

Barnyardgrass; Brome; Canarygrass; Crabgrass; Foxtail; Goosegrass; Ryegrass; Foxtails; Shattercane; Volunteer cereals

Example applications

Sugarbeet; Soybeans; Potatoes; Sunflowers; Alfalfa; Vegetables including beans & peas, asparagus, carrots, aubergine; Cotton; Fax; Peanuts; Fruit including melons, peaches; Herbs

Efficacy & activity

Efficcy demonstrated through field trials and long time use.

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/03/2027

GB LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Sweden/Lithuania

Date EC 1107/2009 inclusion expires

31/08/2026

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

Clethodim exhibits stereoisomerism, primarily due to the presence of a chiral centre at the 2-carbon of its ethylthiopropyl side chain and a C=N double bond in its oxime group, which allows for E/Z geometrical isomerism. These structural features give rise to multiple isomeric forms, including diastereomers and enantiomers. In commercial formulations, clethodim is typically present as a mixture of isomers, with the (E)-oxime configuration being predominant due to its greater stability and herbicidal efficacy. Additionally, clethodim undergoes keto-enol tautomerism in its cyclohexenone ring.

Chemical formula

C₁₇H₂₆ClNO₃S

Canonical SMILES

CCC(=C1C(=O)CC(CC1=O)CC(C)SCC)NOCC=CCl

Isomeric SMILES

CCC(=C1C(=O)CC(CC1=O)CC(C)SCC)NOC/C=C/Cl

International Chemical Identifier key (InChIKey)

SILSDTWXNBZOGF-JWGBMQLESA-N

International Chemical Identifier (InChI)

InChI=1S/C17H26ClNO3S/c1-4-14(19-22-8-6-7-18)17-15(20)10-13(11-16(17)21)9-12(3)23-5-2/h6-7,12-13,20H,4-5,8-11H2,1-3H3/b7-6?,19-14+

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Cyclohexanedione herbicide; Cyclohexene oxime herbicide

Minimum active substance purity

>930 g kg⁻¹

Known relevant impurities

EU dossier - toluene < 4g kg⁻¹

Substance origin

Synthetic

Mode of action

Selective, systemic. Acetyl CoA carboxylase inhibitor (ACCase) - distrupts fatty acid biosynthesis and lipid formation.

CAS RN

99129-21-2

EC number

619-396-7

CIPAC number

508

US EPA chemical code

121011

PubChem CID

135491728

CLP index number

606-150-00-9

Molecular mass

359.92

PIN (Preferred Identification Name)

(5E)-2-[(1?)-N-{[(2E)-3-chloroprop-2-en-1-yl]oxy}propanimidoyl]-5-[(2?)-2-(ethylsulfanyl)propyl]-3-hydroxycyclohex-2-en-1-one

IUPAC name

2-[(E)-N-[(E)-3-chloroprop-2-enoxy]-C-ethylcarbonimidoyl]-5-(2-ethylsulfanylpropyl)-3-hydroxycyclohex-2-en-1-one

CAS name

2-[(1E)-1-[[[(2E)-3-chloro-2-propenyl]oxy]imino]propyl]-5-[2-(ethylthio)propyl]-3-hydroxy-2-cyclohexen-1-one

Forever chemical

Other status information

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

Many recorded cases, Alopecurus myosuroides, Avena fatua, Bromus tectorum, Hordeum leporinum

Physical state

Viscous amber to green-yellow coloured oily liquid depending upon purity

Commercial

Property

Value

Availability status

Current

Introduction & key dates

1987, first reported

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

Arysta LifeSciences France
Agan Chemicals
Loveland Products
BOC Sciences
Nutrien Ag Solutions Limited

Example products using this active

Select 12 SC
Select 240
Centurion
Aceto Clethodim
Agsaver Clethodim
Arc-Clethodim
Clethora 240EC

Formulation and application details

Usually available as an emulsifiable concentrate that is as an aquous foliar spray

Commercial production

The commercial production of clethodim involves a multi-step synthetic process built around constructing its cyclohexenone core and attaching key functional groups. One efficient route begins with the synthesis of the intermediate (E)-O-(3-chloro-2-propenyl)hydroxylamine, which is prepared via a continuous flow process from hydroxylamine hydrochloride, streamlining reaction time and improving safety. This intermediate is then coupled with a substituted cyclohexenone derivative, typically through condensation and acylation reactions, to form the final clethodim molecule. Alternative methods involve reacting 3,4-dihydro-3-methyl-2H-1,4-benzoxazine with dichloroacetyl chloride under reflux, followed by distillation and recrystallisation to yield high-purity clethodim.

Impact on climate of production and use

Data for the amount of life cycle GHGs produced by clethodim are not available in the public domain. However, whilst estimates vary, more general data suggests that between 18 and 27 kilograms of CO₂e is emitted per kilogram of herbicide produced.

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

5450

High

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

100000

Xylene

100000

Methanol

900000

Acetone

900000

Ethyl acetate

Melting point (°C)

-80

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

133.0

Flashpoint (°C)

108.5

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

3.16 X 10⁰¹

Calculated

Log P

1.50

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.16

Dissociation constant pKa) at 25 °C

4.47

Weak acid

Vapour pressure at 20 °C (mPa)

2.68 X 10^-02

Low volatility

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

1.4 X 10^-07

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: 201nm=16500, 282nm=24700
Acidic solution: 206nm=10100, 261.5nm=11800
Basic solution: 201nm=16500, 282.5nm=22100

Surface tension (mN m⁻¹)

49.9

at 20°C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

0.54

Non-persistent

DT₅₀ (lab at 20 °C)

0.54

Non-persistent

DT₅₀ (field)

Non-persistent

DT₉₀ (lab at 20 °C)

2.61

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier 2023: Lab studies DT₅₀ (normalised) range 0.17-2.6 days, Soils=5; EU dossier 2010: Lab studies DT₉₀ range 0.76-8.50 days; Other studies: DT₅₀ 1-3 days (R3)

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

Note

Aqueous photolysis DT₅₀ (days) at pH 7

Value

5.45

at 25°C

Moderately fast

Note

pH sensitive: DT₅₀ 1.6 at pH 5, 7.79 at pH 9 all at 25 °C

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

Value

Stable

Note

pH sensitive: DT₅₀ 28 days at pH 5, stable pH 7 and pH 9 all at 25 °C

Water-sediment DT₅₀ (days)

13.9

Fast

Water phase only DT₅₀ (days)

7.0

Moderately fast

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)

K_oc (mL g⁻¹)

Notes and range

Freundlich

K_f (mL g⁻¹)

0.721

Mobile

K_foc (mL g⁻¹)

44.6

¹/_n

0.982

Notes and range

EU dossier 2023: K_f range 0.22-4.07 mL g⁻¹, K_foc range 6.98-203 mL g⁻¹, ¹/_n range 0.931-1.034, Soils=4; EU dossier 2010: K_f range 0.065-0.112, K_foc range 2.71-43.17, ¹/_n range 0.97-1.04, Soils=3

pH sensitivity

Yes

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.12

Calculated

Low leachability

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

Value

2.50 X 10^-03

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Mobile

Calculated

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

0.82

Calculated using the Atkinson method. Assumed 1.5E+06 OH/cm³, 12 hr

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

3.5

Whole fish

Low potential

CT₅₀ (days)

4.9

Known soil metabolites

Metabolite

Major/Minor fraction

$Click here for further information on Major/Minor fraction$

Estimated maximum occurrence fraction

Notes

clethodim sulfoxide

Major fraction

0.734

clethodim sulfone

Major fraction

0.422

clethodim oxazole sulfone

Major fraction

0.100

clethodim isoxazole

Minor fraction

Anaerobic

clethodim oxazole sulfoxide

Minor fraction

0.06

clethodim oxazole

Minor fraction

clethodim imine sulfoxide

Minor fraction

Known groundwater metabolites

Metabolite

EC SANCO/221/2000 relevancy

ADI (mg kg⁻¹ bodyweight day⁻¹)

WHO drinking water guidance value (μg L⁻¹ day⁻¹)

clethodim oxazole sulfoxide

Not relevant

clethodim sulfone

Not relevant

clethodim sulfoxide

Not relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

clethodim imine ketone

Water (Photolysis)

clethodim oxazole sulfoxide

Water (Photolysis)

3-chloropropenal

Water (Photolysis)

clethodim oxazole sulfide

Water (Photolysis)

clethodim trione sulfoxide

Water (Photolysis)

clethodim chloroallyl alcohol

Water (Photolysis)

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1133

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

Rat

High

(ppm diet)

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

133.7

Unknown species Reproductive NOAEL

Moderate

Birds - Acute LD₅₀ (mg kg⁻¹)

> 1660

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 851 mg kg bw⁻¹ day⁻¹

Anas platyrhynchos

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

Colinus virginianus NOEL

Moderate

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

27.0

Eisenia andrei corr

Moderate

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

Soil micro-organisms

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

Dose: 2.7 mg kg⁻¹ effects may be significant at higher doses

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

171.0

Folsomia candida

Non-target plants

Vegetative vigour ER₅₀ (g ha⁻¹)

4.7

6 plant species tested

Seedling emergence ER₅₀ (g ha⁻¹)

> 270.4

6 plant species tested

Honeybees (Apis spp.)

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

> 199.2

Apis mellifera

Low

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

> 215.1

Apis mellifera

Low

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

Chronic 10 day LDD₅₀ as µg bee⁻¹/day

10.64

Apis mellifera

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 g ha⁻¹, Std lab test

> 325.5

Chrysoperla carnea

Low

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹, Std lab test

> 27.6

Aphidius rhopalosiphi

Moderate

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹, Std lab test

< 7.8

Typhlodromus pyri

Moderate

Beneficial insects (Ground beetles) as Mortality LR₅₀ g ha⁻¹, Std lab test

> 221

Poecilus cupreus

Low

Aquatic ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

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

Oncorhynchus mykiss

Moderate

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

3.9

Oncorhynchus mykiss

Moderate

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

> 103

Danio rerio

Low

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

> 100

Daphnia magna

Low

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)

1.842

Chironomus sinicus

Moderate

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

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

Aquatic Plants (free-floating, fonds growth, fresh) - 7 day (mg l⁻¹) (ErC₅₀, Static)

3.78

Lemna gibba

Moderate

Aquatic plants (rooted, growth rate, fresh) - 14 day (mg l⁻¹)

Algae - Acute (growth rate, fresh; mg l⁻¹) (72 hr ErC₅₀, Static)

35.1

Raphidocelis subcapitata

Low

Algae - Chronic (growth rate, fresh; mg l⁻¹)

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)

1133

Rat

Moderate

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

4167

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

< 3.25

Rat 4 hr (whole body)

Other Mammal toxicity endpoints

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

0.16

Rat SF=100

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

None allocated

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

None allocated

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

0.20

Dog SF=100

Dermal penetration studies (%)

2.7-10.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

Acceptable risk for proposed uses

Occupational

Acceptable risk for proposed uses

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

GB MRL levels for some commodities subject to change in late 2021

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

0.1

EU Dir 89/778/EC limit; Calc MAC=25.0 µg l⁻¹

Mammalian dose elimination route and rate

Urinary: 80-86% in 24 h; faecal 8.5-14% in 24 h. Extensively metabolised.

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

Reproduction / development effects

Acetyl cholinesterase inhibitor

Neurotoxicant

Respiratory tract irritant

Skin irritant

Skin sensitiser

Eye irritant

Phototoxicant

General human health issues

Moderately toxic
Possible liver and blood toxicant

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising

CLP classification 2013

Health: H302, H317, H373
Environment: H412

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

Limited shelf-life.

TRANSLATIONS

Language

Name

English

clethodim

French

clethodim

German

Clethodim

Danish

clethodim

Italian

cletodim

Spanish

cletodin

Greek

Polish

kletodym

Swedish

kletodim

Hungarian

kletodim

Dutch

Norwegian

Record last updated:	22/08/2025
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