Diquat dibromide

Diquat dibromide	Last updated: 17/01/2021
(Also known as: diquat; deiquat; reglone)

SUMMARY

Diquat dibromide is an EU approved contact desiccant and herbicide. It is highly soluble in water, has a low risk of leaching to groundwater and is volatile. It is very persistent in soil but rapidly degrades in aquatic systems. It is moderately toxic to mammals and is a known irritant but no other significant human health issues have been identified. It is moderately toxic to birds, most aquatic organisms, honeybees and earthworms.

GENERAL INFORMATION

Description

A non-residual bupyridyl herbicide and crop desiccant used mainly to control broad-leaved weeds and grasses

Example pests controlled

Water lettuce; Water hyacynth; Duckweed; Pennywort; Annual bluegrass; Fescue; Henbit; Buttercup

Example applications

Potatoes; Oilseed rape; Fruit including apples, pears, peaches, plums, citrus, olive, grapes; Tomatoes; Sunflowers; Vegetables including beans & peas, carrots, onions, chicory; Sugarbeet

Efficacy & activity

Availability status

Current

Introduction & key dates

1958, first reported; 1962, first marketed

UK regulatory status

UK COPR regulatory status

Not approved

Date COPR inclusion expires

Expired

UK LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Not approved

Dossier rapporteur/co-rapporteur

UK/Sweden

Date EC 1107/2009 inclusion expires

Expired

EU Candidate for substitution (CfS)

Not applicable

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

Chemical structure

Isomerism

None

Chemical formula

C₁₂H₁₂N₂Br₂

Canonical SMILES

C1C[N+]2=CC=CC=C2C3=CC=CC=[N+]31.[Br-].[Br-]

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

ODPOAESBSUKMHD-UHFFFAOYSA-L

International Chemical Identifier (InChI)

InChI=1S/C12H12N2.2BrH/c1-3-7-13-9-10-14-8-4-2-6-12(14)11(13)5-1;;/h1-8H,9-10H2;2*1H/q+2;;/p-2

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
diquat dibromide	-

General status

Pesticide type

Herbicide

Substance group

Bipyridylium

Minimum active substance purity

95% w/w

Known relevant impurities

EU dossier - dibromoethane; 2,2-bipyridine; terpyridine & related isomers

Substance origin

Synthetic

Mode of action

Non-selective, contact absorbed through foliage, some desiccant action. Photosystem I (electron transport) inhibitor.

CAS RN

85-00-7

EC number

201-579-4

CIPAC number

US EPA chemical code

032201

PubChem CID

6794

Molecular mass

344.05

PIN (Preferred Identification Name)

6,7-dihydrodipyrido[1,2-a:2',1'-c]pyrazine-5,8-diium dibromide

IUPAC name

9,10-dihydro-8a,10a-diazoniaphenanthrene dibromide

CAS name

6,7-dihydrodipyrido[1,2-a:2',1'-c]pyrazinediium dibromide

Other status information

Potential groundwater contaminant; PAN listed Highly Hazardous Chemical

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

Physical state

White/yellow crystals

Related substances & organisms

paraquat

diquat

glyphosate

Formulations

Property

Value

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

Reglone
Retro
Quad
Googly
Weedol
Reglox

Example products using this active

AgriGuard
Clayton
Standon
Syngenta
ICI Plant Protection

Formulation and application details

Often supplied as a soluble concentrate, gel or liquid concentrate

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

718000

High

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

25000

Methanol

100

Acetone

100

Toluene

100

Ethyl acetate

Melting point (°C)

Decomposes before melting

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

325

Flashpoint (°C)

Not expected to self ignite; Not highly flammable

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

2.51 X 10^-05

Calculated

Log P

-4.6

Low

Bulk density (g ml⁻¹)

1.61

Dissociation constant pKa) at 25 °C

Not applicable

No dissociation

Vapour pressure at 20 °C (mPa)

0.01

Low volatility

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

5.00 X 10^-12

Non-volatile

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

204nm, 272nm, 310nm

Surface tension (mN m⁻¹)

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

2345

Very persistent

DT₅₀ (lab at 20 °C)

365

Very persistent

DT₅₀ (field)

5500

Very persistent

DT₉₀ (lab at 20 °C)

DT₉₀ (field)

DT₅₀ modelling endpoint

Note

EU dossier lab studies DT₅₀ range 598 to >1000 days; DT₉₀ range 1985-20509 days; Other data: DT₅₀ Lab studies - no measureable degradation after 1 year, field study DT₅₀ range 1-20 years (UK)

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

Moderately fast

Note

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

Value

Stable

Note

Stable pH 5 to pH 9

Water-sediment DT₅₀ (days)

Fast

Water phase only DT₅₀ (days)

Moderately fast

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

Non-mobile

K_oc

2184750

Notes and range

Freundlich

K_f

1740

Non-mobile

K_foc

78274

¹/_n

3.85

Notes and range

K_f range 288-7222 mL g⁻¹; K_foc range 14400-144440 mL g⁻¹; ¹/_n range 1.7-5.0, Soils=9

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

-3.34

Calculated

Low leachability

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

Value

5.35 X 10^-03

Calculated

Note

Estimated concentrations of chemicals with Koc values greater than 9995 ml g⁻¹ are beyond the scope of the regression data used in SCI-GROW development. If there are concerns for such chemicals, a higher tier groundwater exposure assessment should be considered, regardless of the concentration returned by SCI-GROW

Potential for particle bound transport index

High

Calculated

Potential for loss via drain flow

Non-mobile

Calculated

Key metabolites

Metabolite

Formation medium

Estimated maximum occurrence fraction

1107/2009 relevancy

1-oxo-1,2,3,4-tetrahydropyrido(1,2-a)pyrazin-5-ium (Ref: R32245)

Soil

0.099

Minor fraction; Relevant

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

Metabolising enzymes

1,2,3,4-tetrahydro-1-oxopyrido(1,2-a) pyrazin-5-ium ion

Water (Photolysis)

ECOTOXICOLOGY

Property

Value

Source; quality score; and other information

Interpretation

Bio-concentration factor

BCF (l kg⁻¹)

Whole fish

Low potential

CT₅₀ (days)

Not available

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

1000

Rat

Moderate

Mammals - Short term dietary NOEL

(mg kg⁻¹)

8.9

Rat

High

(ppm diet)

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

Birds - Acute LD₅₀ (mg kg⁻¹)

Anas platyrhynchos

High

Birds - Short term dietary (LC₅₀/LD₅₀)

721 mg kg feed⁻¹

Coturnix japonica as diquat ion

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

Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

67.0

Oncorhynchus mykiss

Moderate

Fish - Chronic 21 day NOEC (mg l⁻¹)

0.22

Pimephales promelas

Moderate

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

1.2

Daphnia magna

Moderate

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

0.125

Daphnia magna

Moderate

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

2.0

Americamysis bahia

Moderate

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

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

1.27

Chironomus riparius

Moderate

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

> 100

Chironomus riparius

Low

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

0.0032

Lemna gibba

High

Non-target plants

15.4

Brassica oleracea
Vegetative vigour, ER₅₀
as g ha⁻¹

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

> 0.011

Psuedokirchneriella subcapitata

Moderate

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

0.0068

Unknown species

Moderate

Honeybees (Apis spp.)

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

> 20.1

Moderate

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

50.7

Moderate

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

24.3

Moderate

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 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)

94.3

Eisenia foetida

Moderate

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

Eisenia foetida

Moderate

Other soil macro-organisms

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

Other arthropod (1)

LR₅₀ g ha⁻¹

2.9

Typhlodromus pyri

% Effect

90 / 0

Mortality / Fecundity [Dose: Field rate 5 l ha⁻¹]
Aphidius rhopalosiphi

Other arthropod (2)

LR₅₀ g ha⁻¹

3.2

Aphidius rhopalosiphi

% Effect

98 / -58

Mortality / Parasitism [Dose: 1 kg ha⁻¹]
Trichogramma cacocecie adult

Soil micro-organisms

Nitrogen mineralisation: No significant adverse effect [Dose: 50 kg ha⁻¹]
Carbon mineralisation: No significant adverse effect [Dose: 720 kg ha⁻¹]

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)

1000

Rat

Moderate

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

2000

Rat

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 0.5

Rat

Other Mammal toxicity endpoints

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

0.0024

Rat SF=100

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

0.024

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)

0.0024

Dog SF=100

Dermal penetration studies (%)

0.5

Dangerous Substances Directive 76/464

Exposure Routes

Public

Slight risk of dietary exposure

Occupational

European MRLs

EU MRL pesticide database

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

No data found

General human health issues

Potential liver, kidney, stomach and intestine toxicant
Fatal if inhaled

Handling issues

Property

Value and interpretation

General

IMDG Transport Code is usually 6.1 or 8
Corrosive to most metals & may form flammable and explosive H2 gas when in contact with aluminum
May decompose at high temperatures to form toxic gases

CLP classification 2013

Health: H302, H315,H317, H319, H330, H335, H372
Environment: H400, H410

EC Risk Classification

T+ - Very toxic: R26
T - Toxic: R48/25
Xn - Harmful: R22, R43
Xi - Irritant: R36/37/38
N - Dangerous for the environment: R50, R53

EC Safety Classification

S1/2, S28, S36/37/39, S45, S60, S61

WHO Classification

II (Moderately hazardous)

UN Number

2781 for active, products usually 1760

Waste disposal & packaging

Packaging Group III (minor danger)

TRANSLATIONS

Language

Name

English

diquat dibromide

French

diquat dibromure

German

Deiquat dibromid

Danish

diquat dibromid

Italian

diquat dibromid

Spanish

dicuat dibromid

Greek

diquat dibromid

Polish

dibromek dikwatu

Swedish

dikvat dibromidsalt

Hungarian

diquat dibromide

Dutch

diquatdibromide

Record last updated:	17/01/2021
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