Metribuzin (Ref: DPX G2504)

Metribuzin (Ref: DPX G2504)	Last updated: 22/02/2021
(Also known as: metribuzine; DIC 1468; AE F055208)

GENERAL INFORMATION

Description

A pre- and post-emergence herbicide used to control weeds in cereals and a range of other crops

Example pests controlled

Grasses; Broad-leaved weeds

Example applications

Soybeans; Potatoes; Barley, Wheat; Asparagus; Sugarcane; Tomatoes; Peas; Lentils

Efficacy & activity

Efficiacy demonstrated through extensive use and field trials

Availability status

Current

Introduction & key dates

1968, first reported; 1971, first marketed

UK regulatory status

UK COPR regulatory status

Approved

Date COPR inclusion expires

31/07/2024

UK LERAP status

Buffer probably required in UK - see product label

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Estonia/Germany

Date EC 1107/2009 inclusion expires

31/07/2021

EU Candidate for substitution (CfS)

Yes - two 'Persistent-Bioaccumulative-Toxic' criteria

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
✓	✓	✓	✓	✓	✓	✓	✓	✓

Also used in

Australia

Chemical structure

Isomerism

None

Chemical formula

C₈H₁₄N₄OS

Canonical SMILES

CC(C)(C)C1=NN=C(N(C1=O)N)SC

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

FOXFZRUHNHCZPX-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C8H14N4OS/c1-8(2,3)5-6(13)12(9)7(14-4)11-10-5/h9H2,1-4H3

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
metribuzin	-

General status

Pesticide type

Herbicide

Substance group

Triazinone

Minimum active substance purity

930 g kg⁻¹

Known relevant impurities

EU dossier - None declared

Substance origin

Synthetic

Mode of action

Selective, systemic with contact and residual activity. Inhibits photosynthesis (photosystem II).

CAS RN

21087-64-9

EC number

244-209-7

CIPAC number

283

US EPA chemical code

101101

PubChem CID

30479

Molecular mass

214.29

PIN (Preferred Identification Name)

IUPAC name

4-amino-6-tert-butyl-4,5-dihydro-3-methylthio-1,2,4-triazin-5-one

CAS name

4-amino-6-(1,1-dimethylethyl)-3-(methylthio)-1,2,4-triazin-5(4H)-one

Other status information

Potential groundwater contaminant

Relevant Environmental Water Quality Standards

Herbicide Resistance Classification (HRAC)

Herbicide Resistance Classification (WSSA)

Insecticide Resistance Classification (IRAC)

Not applicable

Fungicide Resistance Classification (FRAC)

Not applicable

Examples of recorded resistance

Amaranthus hybridus

Physical state

White crystalline solid

Related substances & organisms

flufenacet

Formulations

Property

Value

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

Artist
Lexone 2
Sencorex WG
Shotput
Sencor

Example products using this active

AgriGuard
Bayer CropScience
DuPont
Greencrop
Makhteshim-Agan

Formulation and application details

Often supplied as wettable powders, liquid suspensions or water-dispersible granules

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

10700

High

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

820

n-Heptane

60000

Xylene

250000

Ethyl acetate

449400

Acetone

Melting point (°C)

125.3

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

230

Flashpoint (°C)

Not expected to self ignite; Not highly flammable

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

5.62 X 10⁰¹

Calculated

Log P

1.75

Low

Bulk density (g ml⁻¹)

1.26

Dissociation constant pKa) at 25 °C

1.3

Strong acid, pKa(2) = 12.8

Vapour pressure at 20 °C (mPa)

0.121

Low volatility

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

0.25 X 10^-04

Non-volatile

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

294nm = 8175 (mean)

Surface tension (mN m⁻¹)

63.1

at 20°C

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Not readily biodegradable

Soil degradation (days) (aerobic)

DT₅₀ (typical)

7.03

Non-persistent

DT₅₀ (lab at 20 °C)

7.03

Non-persistent

DT₅₀ (field)

Non-persistent

DT₉₀ (lab at 20 °C)

24.0

Non-persistent

DT₉₀ (field)

DT₅₀ modelling endpoint

7.1

geometric mean of normalised values

Note

EU 2019 dossier DT₅₀ (normalised) lab studies range 5.98-7.76 days, DT₉₀ range 20.68-25.8 days, Soils=4

Dissipation rate RL₅₀ on plant matrix

Value

Note

Dissipation rate RL₅₀ on and in plant matrix

Value

Note

Aqueous photolysis DT₅₀ (days) at pH 7

Value

0.2

Fast

Note

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

Value

Stable

Note

Stable pH 4 to pH 9 at 25 °C over 34 days. Stable pH 4 and pH 7 at 50 °C, some hydrolysis at pH 9 and 50 °C but slow

Water-sediment DT₅₀ (days)

Moderately fast

Water phase only DT₅₀ (days)

Stable

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

K_oc

Notes and range

Freundlich

K_f

0.874

Mobile

K_foc

48.3

¹/_n

0.922

Notes and range

EU 2019 dossier kf range 0.303-1.9 mL g⁻¹, K_foc range 26.8-81.5 mL g⁻¹, ¹/_n 0.89-0.95, Soils=6

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

2.96

Calculated

High leachability

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

Value

1.99 X 10^-01

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Mobile

Calculated

Key metabolites

Metabolite

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

diketo-metribuzin (Ref: BCS-AG59919)

Soil

0.051

Minor fraction, Relevant

desaminodiketo-metribuzin

Soil

0.094

Minor fraction, Relevant

desamino-metribuzin (Ref: BCS-AA91084)

Soil

0.075

Minor fraction, Relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

Metabolising enzymes

4-amino-6-(1,1-dimethylethyl)-1,2,4-triazine-5(4H)-one

desmethylthio-metribuzin

Groundwater

6-tert-butyl-4,5-dihydro-1,2,4-triazin-5-one-3-mercapturic acid

Groundwater

6-(1-hidroxy-1-methyl-ethyl)-3-methylsulfanyl-4H-[1,2,4]-triazine-5-one

t-BuOH-desamino-metribuzin; metribuzin metabolite M05

Rat

4-methyl-6-(1,1-dimethylethyl)-1,2,4-triazine-3,5(2H,4H)-dione

4-methyl-desamino-diketo-metribuzin; metribuzin metabolite M17

Groundwater

ECOTOXICOLOGY

Property

Value

Source; quality score; and other information

Interpretation

Bio-concentration factor

BCF (l kg⁻¹)

Low potential

CT₅₀ (days)

Not available

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

322

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

2.2

Rat

High

(ppm diet)

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

3.3

Rat Reproductive NOAEL

High

Birds - Acute LD₅₀ (mg kg⁻¹)

164

Colinus virginianus

Moderate

Birds - Short term dietary (LC₅₀/LD₅₀)

> 359 mg kg bw⁻¹ day⁻¹

Colinus virginianus

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

Colinus virginianus NOAEL

Moderate

Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

74.6

Oncorhynchus mykiss

Moderate

Fish - Chronic 21 day NOEC (mg l⁻¹)

5.6

Oncorhynchus mykiss growth

Moderate

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

Daphnia magna

Moderate

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

0.305

Daphnia magna

Moderate

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 - Acute 7 day EC₅₀, biomass (mg l⁻¹)

0.0161

Lemna gibba

Moderate

Non-target plants

15.7

Brassica napus
Seedling emergence, ER₅₀
as g ha⁻¹

12.3

Brassica napus
Vegetative vigour, ER₅₀
as g ha⁻¹

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

0.0266

Desmodesmus subspicatus

Moderate

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

0.019

Unknown species

Moderate

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)

> 76.7

Apis mellifera

Moderate

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

Bumblebees (Bombus spp.)

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

> 100

Bombus terrestris

Low

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

> 140

Bombus terrestris

Low

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 pollinators (1)

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

Mode of exposure

Other pollinators (2)

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

Mode of exposure

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

427

Eisenia foetida

Moderate

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

> 52.3

Eisenia foetida 56 days

Moderate

Other soil macro-organisms

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Other arthropod (1)

LR₅₀ g ha⁻¹

34.1

48 hour
Aphidius rhopalosiphi

% Effect

Other arthropod (2)

LR₅₀ g ha⁻¹

40.1

Typhlodromus pyri

% Effect

Soil micro-organisms

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

Dose: Not stated 28 days

Mesocosm study data

NOEAEC mg l⁻¹

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)

322

Rat

Moderate

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

5000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

2.05

Rat 4 hr (dust nose only)

Other Mammal toxicity endpoints

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

0.013

Rat SF=100

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

0.02

SF=100

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

No data

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

0.02

SF=100

Dermal penetration studies (%)

0.3-20.0

concentration dependent

Dangerous Substances Directive 76/464

Exposure Routes

Public

No unacceptable risks to bystanders identified

Occupational

Minimal risk for operators using protection clothing and equipment

MRLs

European

EU MRL pesticide database

Notes

Drinking Water Standards

Drinking Water MAC (μg l⁻¹)

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

Endocrine issues - Hyperthyroidism, alteration of somatotropin levels
Thyroid toxicant

Handling issues

Property

Value and interpretation

General

Not explosive or oxidising
IMDG Transport Code is usually 9

CLP classification 2013

Health: H302, H373
Environment: H400, H410

EC Risk Classification

Xn - Harmful: R22
N - Dangerous for the environment: R50, R53

EC Safety Classification

S2, S60, S61

WHO Classification

II (Moderately hazardous)

UN Number

Usually 3077

Waste disposal & packaging

Packaging Group III (minor danger)

TRANSLATIONS

Language

Name

English

metribuzin

French

metribuzine

German

Metribuzin

Danish

metribuzin

Italian

metribuzin

Spanish

metribuzina

Greek

metribuzin

Polish

metrybuzyna

Swedish

metribuzin

Hungarian

metribuzin

Dutch

metribuzine

Record last updated:	22/02/2021
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