Maleic hydrazide

Maleic hydrazide	Last updated: 17/02/2021
(Also known as: maleic hydrazide acid ; MH)

GENERAL INFORMATION

Description

A plant growth regulator used to suppress growth and to induce dormancy in some crops

Example pests controlled

Growth; Suckers; Sprout suppression

Example applications

Lawns; Amenity turf; Non-cropped areas; Fruit including citrus; Potatoes; Carrots; Onions, shallots & garlic; Tobacco; Ornamenial shrubs

Efficacy & activity

Availability status

Current

Introduction & key dates

after 1950

UK regulatory status

UK COPR regulatory status

Approved

Date COPR inclusion expires

31/10/2032

UK LERAP status

None

EC Regulation 1107/2009 (repealing 91/414)

EC Regulation 1107/2009 status

Approved

Dossier rapporteur/co-rapporteur

Denmark/Belgium

Date EC 1107/2009 inclusion expires

31/10/2032

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
		✓	✓	✓	✓	✓	✓	✓

Also used in

Australia, USA

Chemical structure

Isomerism

Chemical formula

C₄H₄N₂O₂

Canonical SMILES

C1=CC(=O)NNC1=O

Isomeric SMILES

No data

International Chemical Identifier key (InChIKey)

BGRDGMRNKXEXQD-UHFFFAOYSA-N

International Chemical Identifier (InChI)

InChI=1S/C4H4N2O2/c7-3-1-2-4(8)6-5-3/h1-2H,(H,5,7)(H,6,8)

2D structure diagram/image available?

Yes

Cambridge Crystallographic Data Centre diagrams

Common Name	Relationship	Link
maleic hydrazide	-

General status

Pesticide type

Plant growth regulator, Herbicide

Substance group

Pyridazine

Minimum active substance purity

979 g kg⁻¹

Known relevant impurities

EU dossier - Hydrazine <= 1 mg kg⁻¹

Substance origin

Synthetic

Mode of action

Suppresses sprout and bud growth, absorbed by leaves and roots and translocated.

CAS RN

123-33-1

Alternative/old CAS RN

10071-13-3

EC number

204-619-9

CIPAC number

310

US EPA chemical code

051501

PubChem CID

21954

Molecular mass

112.1

PIN (Preferred Identification Name)

IUPAC name

6-hydroxy-2H-pyridazin-3-one

CAS name

1,2-dihydro-3,6-pyridazinedione

Other status information

Chemical subject to PIC regulations

Relevant Environmental Water Quality Standards

Herbicide Resistance Classification (HRAC)

None allocated

Herbicide Resistance Classification (WSSA)

None allocated

Insecticide Resistance Classification (IRAC)

Not applicable

Fungicide Resistance Classification (FRAC)

Not applicable

Examples of recorded resistance

Physical state

White crystalline solid

Formulations

Property

Value

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

Fazor
Source II
Retard
Sprout Stop
Sucker Stuff

Example products using this active

Bayer CropScience
Dow AgroSciences
Nufarm UK
Vitax Ltd

Formulation and application details

Usually supplied in liquid formulations

ENVIRONMENTAL FATE

Property

Value

Source; quality score; and other information

Interpretation

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

156000

High

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

4200

Methanol

Toluene

Hexane

35.9

Ethyl acetate

Melting point (°C)

298

Boiling point (°C)

Decomposes before boiling

Degradation point (°C)

310

Flashpoint (°C)

Not expected to self ignite; Not highly flammable

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

1.48 X 10^-02

Calculated

Log P

-1.83

Low

Bulk density (g ml⁻¹)

1.61

Dissociation constant pKa) at 25 °C

5.64

Weak acid

Vapour pressure at 20 °C (mPa)

3.1 X 10^-03

Low volatility

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

4.05 X 10^-08

Non-volatile

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

Neutral solution: 326nm = 2444, and 217nm = 16816
Acidic solution: 306nm = 2376 and 223nm = 8052
Basic solution: 328nm = 2462 and 217nm = 16241

Surface tension (mN m⁻¹)

56.5

at 21 °C 99.9%

Degradation

Property

Value

Source; quality score; and other information

Interpretation

General biodegradability

Soil degradation (days) (aerobic)

DT₅₀ (typical)

0.8

Non-persistent

DT₅₀ (lab at 20 °C)

0.8

Non-persistent

DT₅₀ (field)

Non-persistent

DT₉₀ (lab at 20 °C)

5.5

Non-persistent

DT₉₀ (field)

10.4

DT₅₀ modelling endpoint

Note

EU 2016 dossier field studies DT₅₀ range 0.3-2.3 days, DT₉₀ range 1.4-12.9, Soils=7 days; Other sources: DT₅₀ 30 days anaerobic (DW4)

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

Stable

Note

pH sensitive: stable pH 5 to pH 7, DT₅₀ ~34 days at pH 9

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

Value

Stable

Note

Stable pH 3 to pH 9

Water-sediment DT₅₀ (days)

186

Slow

Water phase only DT₅₀ (days)

106

Stable

Soil adsorption and mobility

Property

Value

Source; quality score; and other information

Interpretation

Linear

K_d

0.725

Mobile

K_oc

45.8

Notes and range

EU 2016 dossier K_d range 0.2-1.7 mL g⁻¹, K_oc range 14.5-124.3 mL g⁻¹; Other sources: 250 mL g⁻¹ (DW3)

Freundlich

K_f

0.48

Mobile

K_foc

28.16

¹/_n

0.912

Notes and range

EU 2016 dossier K_f range 0.16-1.51 mL g⁻¹, K_foc range 14.4-108.0, ¹/_n range 0.860-0.987, Soils=4

pH sensitivity

Fate indices

Property

Value

Source; quality score; and other information

Interpretation

GUS leaching potential index

1.22

Calculated

Low leachability

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

Value

2.69 X 10^-03

Calculated

Note

Potential for particle bound transport index

Low

Calculated

Potential for loss via drain flow

Mobile

Calculated

Other known metabolites

Metabolite name and reference

Aliases

Formation medium / Rate

Estimated maximum occurrence fraction

Metabolising enzymes

maleic acid

Soil

ECOTOXICOLOGY

Property

Value

Source; quality score; and other information

Interpretation

Bio-concentration factor

BCF (l kg⁻¹)

Low risk

Based on LogP < 3

Low risk

CT₅₀ (days)

Mammals - Acute oral LD₅₀ (mg kg⁻¹)

> 2000

Rat

Low

Mammals - Short term dietary NOEL

(mg kg⁻¹)

> 25

Dog

High

(ppm diet)

> 750

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

> 1216

Rat Reproductive NOAEL

Low

Birds - Acute LD₅₀ (mg kg⁻¹)

4640

Anas platyrhynchos

Low

Birds - Short term dietary (LC₅₀/LD₅₀)

> 10000 mg kg feed⁻¹

Colinus virginianus

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

542.5

Colinius virginianus LD₅₀/10 NOEC

Low

Fish - Acute 96 hour LC₅₀ (mg l⁻¹)

> 1000

Oncorhynchus mykiss as potassium salt

Low

Fish - Chronic 21 day NOEC (mg l⁻¹)

9.6

Pimephales promelas as potassium salt 32 day

Moderate

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

107.7

Daphnia magna

Low

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

0.95

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)

> 110

Lemna gibba

Low

Non-target plants

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

> 100

Chlorella vulgaris

Low

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

Unknown species

Low

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)

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)

> 1000

Low

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

151.5

Eisenia foetida

Low

Other soil macro-organisms

Acute LC₅₀ (mg kg⁻¹)

Chronic NOEC (mg kg⁻¹)

112.7

Folsomia candida 14d

Other arthropod (1)

LR₅₀ g ha⁻¹

% Effect

Mortality [Dose: 5 kg ha⁻¹]
Aphidius rhopalosiphi

Other arthropod (2)

LR₅₀ g ha⁻¹

% Effect

Mortality [Dose: 5 kg ha⁻¹, 7days]
Typhlodromus pyri

Soil micro-organisms

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

Dose: 5 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)

> 2000

Rat

Low

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

2000

Rabbit

Mammals - Inhalation LC₅₀ (mg l⁻¹)

> 3.2

Rat (nose only)

Other Mammal toxicity endpoints

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

0.25

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)

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

0.25

Dog 1 year SF=100

Dermal penetration studies (%)

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

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

Potential liver toxicant
Possible mutagen
Ingestion might cause tremors and muscle spasms
IARC group 3 carcinogen

Handling issues

Property

Value and interpretation

General

IMDG Transport Code is usually 9
Not explosive or oxidising

CLP classification 2013

Health: H315, H319, H341, H335

EC Risk Classification

Xi - Irritant: R36/37/38

EC Safety Classification

S26, S36

WHO Classification

U (Unlikely to present an acute hazard)

UN Number

Usually 3077

Waste disposal & packaging

Packaging Group III (minor danger)

TRANSLATIONS

Language

Name

English

maleic hydrazide

French

hydrazide maleique

German

Maleinhydrazid

Danish

maleinhydrazid

Italian

idrazide maleica

Spanish

hidrazida maleica

Greek

Polish

hydrazyd maleinowy

Swedish

maleinhydrazid

Hungarian

maleic hydrazide

Dutch

maleine hydrazide

Record last updated:	17/02/2021
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