Metalaxyl-M (Ref: CGA 329351)

Metalaxyl-M (Ref: CGA 329351)	Last updated: 22/05/2025
(Also known as: mefenoxam; R-metalaxyl)

SUMMARY

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: Drainflow: Mobile	Ecotoxicity Moderate alert: Birds acute ecotoxicity: Moderate; Birds chronic ecotoxicity: Moderate; Fish chronic ecotoxicity: Moderate; Daphnia chronic ecotoxicity: Moderate; Bees acute oral ecotoxicity: Moderate; Earthworms acute ecotoxicity: Moderate; Earthworms chronic ecotoxicity: Moderate	Human health Moderate alert: Mammals acute toxicity: Moderate

GENERAL INFORMATION

Description

A fungicide used to control diseases caused by air- and soil-borne pathogens

Example pests controlled

Foliar and tuber blight; Downy mildews (Pseudoperonospora humuli; Plasmopara halstedii); Blight (Phytophthora infestans); Blue mold (Peronospora tabacina)

Example applications

Potatoes; Tomatoes; Hops; Lettuce; Vegetables; Tobacco; Sunflower, Spinach; Grapes; Sugar beet; Fodder beet; Vining peas; Peaches

Efficacy & activity

Availability status

Current

Introduction & key dates

1996, first reported & introduced USA

GB regulatory status

GB COPR regulatory status

Approved

Date COPR inclusion expires

31/05/2035

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

Belgium/Greece

Date EC 1107/2009 inclusion expires

31/05/2035

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

Metalaxyl-M is the biologically active enantiomer (R-form) of the isomeric compound metalaxyl, It consists of a minimum of 97% of the R-enantiomer and 3% of the S-enantiomer.

Chemical formula

C₁₅H₂₁NO₄

Canonical SMILES

CC1=C(C(=CC=C1)C)N(C(C)C(=O)OC)C(=O)COC

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

ZQEIXNIJLIKNTD-GFCCVEGCSA-N

International Chemical Identifier (InChI)

InChI=1S/C15H21NO4/c1-10-7-6-8-11(2)14(10)16(13(17)9-19-4)12(3)15(18)20-5/h6-8,12H,9H2,1-5H3/t12-/m1/s1

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
metalaxyl	Unstated isomer

General status

Pesticide type

Fungicide

Substance groups

Anilide fungicide; Acylamino acid fungicide

Minimum active substance purity

910 g kg⁻¹

Known relevant impurities

EU dossier - 2,6-dimethyl-phenylamine; 4-methoxy-5-methyl-5H-(1,2)oxathiole 2,2-dioxide < 0./5 g kg⁻¹; 4-methoxy-5-methyl-5H-1,2oxathiole 2,2-dioxide < 1 g kg⁻¹

Substance origin

Synthetic

Mode of action

Systemic with curative and protective action. Disrupts fungal nucleic acid synthesis - RNA ploymerase 1.

CAS RN

70630-17-0

EC number

615-135-6

CIPAC number

580

US EPA chemical code

PubChem CID

11150163

CLP index number

612-163-00-0

Molecular mass

279.33

PIN (Preferred Identification Name)

IUPAC name

methyl N-(methoxyacetyl)-N-(2,6-xylyl)-D-alaninate

CAS name

methyl N-(2,6-dimethylphenyl)-N-(methoxyacetyl)-D-alaninate

Other status information

Relevant Environmental Water Quality Standards

Herbicide Resistance Class (HRAC MoA class)

Not applicable

Herbicide Resistance Class (WSSA MoA class)

Not applicable

Insecticide Resistance Class (IRAC MoA class)

Not applicable

Fungicide Resistance Class (FRAC MOA class)

Examples of recorded resistance

Physical state

Clear to pale yellow viscous liquid with weak odour at 97.2% purity, darkens with reducing purity

Formulations

Property

Value

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

Fargro
Syngenta
Clayton
ADAMA Australia Pty Ltd

Example products using this active

Folio
Fubol Gold
SL567
Wakil XL
Apron XL
Axiom Flexi
Ridomil Gold

Formulation and application details

Often supplied as a soluble concentrate or a water dispersible granule formulation that is mixed with water and used as a spray

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

26000

High

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

59000

n-Hexane

Miscible

Toluene

Miscible

Methanol

Miscible

Acetone

Melting point (°C)

-38.7

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

270

Flashpoint (°C)

179

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

5.13 X 10⁰¹

Calculated

Log P

1.71

at 25 °C

Low

Fat solubility of residues

Solubility

Insoluble

Data type

Regulatory data

Density (g ml⁻¹)

1.13

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

3.3

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)

3.50 X 10^-05

Non-volatile

Volatilisation as max % of applied dose lost

From plant surface

24 hr

Volatilisation is potentially a concern for short and long range air transport

From soil surface

24 hr

Volatilisation is potentially a concern for short and long range air transport

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

266nm = 512, 274nm = 477, no absorption 290-750nm

Surface tension (mN m⁻¹)

57.6

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

6.64

Non-persistent

DT₅₀ (lab at 20 °C)

6.64

Non-persistent

DT₅₀ (field)

14.1

Non-persistent

DT₉₀ (lab at 20 °C)

48.7

Moderately persistent

DT₉₀ (field)

46.7

DT₅₀ modelling endpoint

6.64

(geometric mean)

Note

EU dossier 2015 lab studies DT₅₀ range 1.38-73.1 days, DT₉₀ range 12.7-87.6 days, field studies DT₅₀ range 9.3-30.9 days DT₉₀ range 30.7-102.6 days

Dissipation rate RL₅₀ (days) on plant matrix

Value

Note

Dissipation rate RL₅₀ (days) on and in plant matrix

Value

8.3

Note

Published literature RL₅₀ range 0.8-28.0 days, 6 field crops, various matrices, n=11

Aqueous photolysis DT₅₀ (days) at pH 7

Value

Stable

Note

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

Value

Stable

Note

Stable at all pH values

Water-sediment DT₅₀ (days)

32.1

Moderately fast

Water phase only DT₅₀ (days)

24.8

Slow

Sediment phase only DT₅₀ (days)

31.8

Stable

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)

1.63

Mobile

K_foc (mL g⁻¹)

50.63

¹/_n

0.955

Notes and range

EU dossier (2023) K_f range 0.07-8.01 mL g⁻¹, K_foc range 20-570 mL g⁻¹, ¹/_n range 0.77-1.45, Soils=25

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.64

Calculated

Transition state

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

Value

1.07 X 10^-01

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

4.8

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)

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

N-(2,6-dimethylphenyl)-N-(methoxyacetyl)alanine (Ref: CGA 62826)

Minor fraction

(R)-2-((2,6-dimethyl-phenyl)-(2-methoxy-acetyl)-amino)-propionic acid (Ref: NOA 409045)

Major fraction

0.720

N-(2,6-dimethyl-phenyl)-2-methoxy-acetamide (Ref: CGA 67868)

Minor fraction

0.06

2-(((R)-1-carboxy-ethyl)-(2-methoxy-acetyl)-amino)-3-methyl-benzoic acid (Ref: SYN 546520)

Minor fraction

0.04

N-(2-carboxy-6-methylphenyl)-N-(methoxyacetyl)alanine (Ref: CGA 108906)

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)

(R)-2-((2,6-dimethyl-phenyl)-(2-methoxy-acetyl)-amino)-propionic acid (Ref: NOA 409045)

Not relevant

0.5

3000

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

(R)-2-((2,6-Dimethyl-phenyl)-(2-methoxy-acetyl)-amino)-propionic acid (Ref: NOA 409045)

Surface water; Sediment

N-(2-carboxy-6-methylphenyl)-N-(methoxyacetyl)alanine (Ref: CGA 108906)
Note: CAS: 104390-56-9; LC50(fish) = 100 mg/l; LC50(Daphnia) = 100 mg/l

Plant

N-(2,6-dimethylphenyl)-N-(hydroxyacetyl)alanine methyl ester (Ref: CGA 67869)
Note: CAS 66637-79-4

N-(carboxycarbonyl)-N-(2,6-dimethylphenyl)alanine methyl ester (Ref: CGA 79353)

N-hydroxyacetyl-2,6-dimethyl-aniline (Ref: CGA 37734)
Note: CAS 29183-14-0

N-(2,6-dimethyl- 5-hydroxyphenyl)-N-(methoxyacetyl)alanine methyl ester (Ref: CGA 100255)
Note: CAS 96258-85-4

N-(2-hydroxymethyl-6-methylphenyl)-N-(methoxyacetyl)alanine methyl ester (Ref: CGA 94689)
Note: CAS 85933-49-9

N-(2-carboxy-6-methylphenyl)-N-(methoxyacetyl)alanine methyl ester (Ref: CGA 108905)

N-(2,6-dimethylphenyl) alanine (Ref: CGA 67867)

N-(carboxycarbonyl)-N-(2,6-dimethylphenyl)alanine (Ref: CGA 78532)

2,6-dimethylanilinoxoacetic acid (Ref: CGA 68124)
Note: CAS 2903-48-2

N-(3-hydroxy-2,6-dimethylphenyl)-N-(methoxyacetyl)alanine (Ref: CGA 119857)

N-(2,6-dimethylphenyl)-N-(hydroxyacetyl)alanine (Ref: CGA 107955)
Note: CAS 104390-55-8

Rat

N-methoxyacetyl-2,6-dimethyl-aniline (Ref: CGA 67868)
Note: LC50(fish) = 98.9 mg/l; LC50(Daphnia) = 158 mg/l

Water

N-(2-hydroxymethyl-6-methylphenyl)-N-(methoxyacetyl)alanine (Ref: -)
Note: CAS 53823-88-4

ECOTOXICOLOGY

Terrestrial ecotoxicology

Property

Value

Source; quality score; and other information

Interpretation

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

375

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

2.5

Rat

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

981

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 5620 mg kg feed⁻¹

Colinus virginianus

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

Colinus virginianus

Moderate

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

830

Eisenia foetida

Moderate

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

35.63

Eisenia foetida

Moderate

Soil micro-organisms

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

Dose: 6.6 mg kg⁻¹ soil 100 Day

Collembola

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

125

Folsomia candida

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)

> 97.3

Apis mellifera

Moderate

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)

Beneficial insects (Parasitic wasps)

Beneficial insects (Predatory mites)

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)

> 100

Oncorhynchus mykiss

Low

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

9.1

Pimephales promelas

Moderate

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

> 221.9

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)

1.2

Daphnia magna as metalaxyl

Moderate

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)

69.5

Lemna gibba

Low

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

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

Unknown species

Low

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)

375

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 2.29

Rat 4 hr (nose only)

Other Mammal toxicity endpoints

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

0.08

Dog SF=100

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

0.5

Dog SF=100

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

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

0.08

Rat 90 day SF=100

Dermal penetration studies (%)

10-75

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks to bystanders identified

Occupational

No unacceptable risks to operators or other workers identified

MRLs

European

EU MRL pesticide database

Great Britain

GB MRL Register

Notes

GB MRL updated September 2022 for oil palm fruits. Consult register.

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

Possible liver toxicant

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising

CLP classification 2013

Health: H302, H318

WHO Classification

Not listed (Not listed)

UN Number

Waste disposal & packaging

Shelf-life, storage, stability and reactivity

TRANSLATIONS

Language

Name

English

metalaxyl-M

French

metalaxyl-M

German

Metalaxyl-M

Danish

metalaxyl-M

Italian

metalaxil-M

Spanish

metalaxil-M; mefenoxam

Greek

metalaxyl-M

Polish

metalaksyl-M

Swedish

metalaxyl-M

Hungarian

metalaxyl-M

Dutch

methalaxyl-M

Norwegian

metalaksyl-M

Record last updated:	22/05/2025
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