Cyhalofop-butyl (Ref: DE 537)

Cyhalofop-butyl (Ref: DE 537)	Last updated: 04/06/2025
(Also known as: XDE 537; XRD 537)

SUMMARY

Cyhalofop-butyl is a rice herbicide. It has a low aqueous solubility and is non-volatile. It is not expected to be persistent in soil systems but may be persistent in some water systems depending on local conditions. Cyhalofop-butyl is moderately toxic to fish and aquatic plants but has a low toxicity to aquatic invertebrates, birds and honeybees. It has a low mammalian oral toxicity.

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 Low alert: Non-persistent; GUS: Low leachability; Drainflow: Non-mobile; Potential for particle bound transport: Low	Ecotoxicity Moderate alert: Fish acute ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health Low alert

GENERAL INFORMATION

Description

A selective herbicide used for post-emergence control of grass weeds usually in rice crops

Example pests controlled

Barnyardgrass; Silver top; Rice flatsedge; Arrowhead; Junglerice; Pigweed; Cocklebur

Example applications

Rice

Efficacy & activity

Availability status

Current

Introduction & key dates

circa 1990, registered Asia

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

30/06/2032

GB LERAP status

No data

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Italy/Austria

Date EC 1107/2009 inclusion expires

30/06/2032

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; Morocco

Chemical structure

Isomerism

A chiral molecule in which the R-isomer is by far the most dominant and often accounts for over 95% of cyhalofop-butyl

Chemical formula

C₂₀H₂₀FNO₄

Canonical SMILES

CCCCOC(=O)C(C)OC1=CC=C(C=C1)OC2=C(C=C(C=C2)C#N)F

Isomeric SMILES

CCCCOC(=O)[C@@H](C)OC1=CC=C(C=C1)OC2=C(C=C(C=C2)C#N)F

International Chemical Identifier key (InChIKey)

TYIYMOAHACZAMQ-CQSZACIVSA-N

International Chemical Identifier (InChI)

InChI=1S/C20H20FNO4/c1-3-4-11-24-20(23)14(2)25-16-6-8-17(9-7-16)26-19-10-5-15(13-22)12-18(19)21/h5-10,12,14H,3-4,11H2,1-2H3/t14-/m1/s1

2D structure diagram/image available?

Yes

General status

Pesticide type

Herbicide

Substance groups

Aryloxyphenoxypropionate herbicide

Minimum active substance purity

950 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Systemic, foliar untake with no soil activity. Acetyl CoA carboxylase inhibitor (ACCase) - distrupts fatty acid biosynthesis and lipid formation.

CAS RN

122008-85-9

EC number

601-817-0

CIPAC number

596

US EPA chemical code

082583

PubChem CID

180089

CLP index number

No data found

Molecular mass

357.38

PIN (Preferred Identification Name)

butyl (2R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propanoate

IUPAC name

butyl (R)-2-[4-(4-cyano-2-fluorophenoxy)phenoxy]propionate

CAS name

butyl (2R)-2-(4-(4-cyano-2-fluorophenoxy)phenoxy)propanoate

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

Echinochloa crus-galli

Physical state

White crystalline solid

Related substances & organisms

cyhalofop

cyhalofop amide

cyhalofop diacid

Formulations

Property

Value

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

Dow AgroSciences
Fertiagro Pte. Ltd.

Example products using this active

Beauty
Frog
Clincher
Rebelex

Formulation and application details

Usually supplied as an emulsifiable concentrate

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

0.44

Low

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

6060

n-Heptane

250000

Xylene

250000

Acetone

250000

Methanol

Melting point (°C)

45.5

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

270

Flashpoint (°C)

122

(open cup)

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

2.09 X 10⁰³

Calculated

Log P

3.32

High

Fat solubility of residues

Solubility

Not relevant

Data type

Regulatory data - negligible residues seen in animal studies

Density (g ml⁻¹)

1.17

Dissociation constant pKa) at 25 °C

Vapour pressure at 20 °C (mPa)

0.053

at 25°C

Low volatility

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

9.51 X 10^-04

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

From soil surface

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

In MeOH: 247.8nm = 16100, 233.4nm = 15900, 202.6nm = 32700
In 1M HCl in MeOH: 247.6nm = 16400, 233.4nm 16400, 202.2nm = 37000, 236.0nm = 17100, 211.6nm = 12300

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

0.2

Non-persistent

DT₅₀ (lab at 20 °C)

0.2

Non-persistent

DT₅₀ (field)

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 0.24-0.85 days, DT₉₀ range 0.8-2.8 days; Other sources: 1.0 day (DW4)

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

4.3

Note

Published literature RL₅₀ range 2.1-8.7 days, 2 field crops, various matrices, n=3

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Slow

Note

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

Value

Moderately persistent

Note

Stable at pH 4, DT₅₀ 2 days at pH 9, 25 °C

Water-sediment DT₅₀ (days)

0.1

Fast

Water phase only DT₅₀ (days)

0.15

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)

Non-mobile

K_oc (mL g⁻¹)

5247

Notes and range

EU dossier K_oc range 2066-9637 ml/g

Freundlich

K_f (mL g⁻¹)

41.5

Slightly mobile

K_foc (mL g⁻¹)

1016

¹/_n

0.878

Notes and range

EU dossier K_f range 11.9-72.3 mL g⁻¹; K_foc range 512-2079 mL g⁻¹, ¹/_n range 0.833-0.960, Soils=5

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

-0.69

Calculated

Low leachability

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

Value

9.96 X 10^-06

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Non-mobile

Calculated

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

6.0

Calculated using the Atkinson method

Below the level of concern for long-range air transport

Bio-concentration factor

BCF (l kg⁻¹)

7.5

Low potential

CT₅₀ (days)

Not available

Known soil metabolites

Metabolite

Major/Minor fraction

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

Estimated maximum occurrence fraction

Notes

cyhalofop diacid (Ref: XDE-537 )

Major fraction

0.865

cyhalofop

Major fraction

0.958

cyhalofop amide

Minor fraction

0.081

Known groundwater metabolites

None

Other 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)

Rat

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

> 2250

Colinus virginianus

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5620 mg kg feed⁻¹

Colinus virginianus

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

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

> 1000

Eisenia foetida

Low

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

as cyhalofop

Moderate

Soil micro-organisms

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

Dose: 1.5 kg ha⁻¹ 28 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

> 5

Folsomia candida as cyhalofop

Non-target plants

Honeybees (Apis spp.)

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

> 100

Apis mellifera

Low

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)

>50% Mortality at dose 83 g ha⁻¹

Chrysoperla carnea

Beneficial insects (Parasitic wasps) as Mortality LR₅₀ g ha⁻¹

174.9

Aphidius rhopalosiphi

Beneficial insects (Predatory mites) as Mortality LR₅₀ g ha⁻¹

2281

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)

0.79

Lepomis macrochirus

Moderate

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

0.13

Oncorhynchus mykiss

Moderate

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

1.05

Danio rerio EC₅₀ Embryo

Moderate

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

> 2.7

Daphnia magna

Moderate

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

100

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)

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

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

> 5.3

Lemna minor

Moderate

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

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

> 0.96

Scenedesmus subspicatus

Moderate

Algae - Chronic 96 hour NOEC, growth (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)

> 5000

Rat

Low

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 5.63

Rat 4 hr (dust; whole body)

Other Mammal toxicity endpoints

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

0.003

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

0.4

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

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

0.013

Dermal penetration studies (%)

1.0-23.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

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

Health issues

Specific human health issues

Carcinogen

Genotoxic

Endocrine disruptor

; ; ; ;

No data found

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

Potential gall bladder, liver & kidney toxicant

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising

CLP classification 2013

Health: H302, H373
Environment: H400, H410

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

cyhalofop-butyl

French

cyhalofop-butyl

German

Cyhalofop-butyl

Danish

cyhalofop-butyl

Italian

cyhalofop-butyl

Spanish

cihalofop-butil

Greek

Polish

cyhalofop butylowy

Swedish

Hungarian

Dutch

Norwegian

Record last updated:	04/06/2025
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