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oxydemeton-methyl (Ref: ENT 24964)
** methylmercaptophos oxide ** R 2170 ** isomethylsystox sulfoxide ** metaisosystox sulfoxide ** BAY 21097 ** Translations

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for oxydemeton-methyl

Description: An insecticide and acaricide for the control of insect pests in both food and non-food situations

Example pests controlled: Aphids including the green peach aphid, mustard aphid; Mites; Thrips; Sawflies

Example applications: Vegetables; Fruit; Field crops; Ornamental shrubs and trees

Availability status: Current

Introduction & key dates: -

EC Regulation 1107/2009 (repealing 91/414):
Status Not approved
Dossier rapporteur/co-rapporteur France
Date inclusion expires Expired

Approved for use () or known to be used () in the following European countries:





























General status:
Pesticide type Insecticide
Substance group Organophosphate
Minimum active substance purity 95%
Known relevant impurities EU dossier - demeton-S-methyl <=3.5% and demeton-S-methyl sulfone <=2%
Substance origin Synthetic
Mode of action Systemic with contact and stomach action. Rapid knockdown effect. Cholinesterase inhibitor.
CAS RN 301-12-2
EC number 206-110-7
CIPAC number 171
US EPA chemical code 058702
Chiral molecule Chiral, a specific isomer or a derivative of a chiral molecule
Chemical formula C6H15O4PS2
International Chemical Identifier key (InChIKey) PMCVMORKVPSKHZ-UHFFFAOYSA-N
International Chemical Identifier (InChI) InChI=1S/C6H15O4PS2/c1-4-13(8)6-5-12-11(7,9-2)10-3/h4-6H2,1-3H3
Structure diagram/image available? Yes
Molecular mass (g mol-1) 246.3
PIN (Preferred Identification Name) -
IUPAC name S-2-ethylsulfinylethyl O,O-dimethyl phosphorothioate
CAS name S-[2-(ethylsulfinyl)ethyl] O,O-dimethyl phosphorothioate
Other status information Potential groundwater contaminant; Chemical subject to PIC regulations
Herbicide Resistance Classification (HRAC) Not applicable
Herbicide Resistance Classification (WSSA) Not applicable
Insecticide Resistance Classification (IRAC) 1B
Fungicide Resistance Classification (FRAC) Not applicable
Examples of recorded resistance Aphis gossypii
Myzocallis coryli
Myzus persicae
Physical state Colourless liquid
Related substances & organisms

Property Value
Example manufacturers & suppliers of products using this active now or historically
  • Gowan
  • Amico Pesticides
  • Makhteshim Agan
  • Bayer
  • Mobay
Example products using this active
  • Metasystox 250EC
  • Oxydemetchem
  • Safasystox
UK LERAP status No UK approval for use or outside scope
Formulation and application details Usually supplied as an emsulsifiable concentrate.


for oxydemeton-methyl

Property Value Source/Quality Score/Other Information Interpretation
Solubility - In water at 20oC (mg l-1) 1200000 A5 High
Solubility - In organic solvents at 20oC (mg l-1) 25 A5 - n-Hexane -
250000 A5 - Toluene -
250000 A5 - 1-Octanol -
250000 A5 - Acetone -
Melting point (oC) -49 A5 -
Boiling point (oC) Decomposes before boiling A5 -
Degradation point (oC) 65 A5 -
Flashpoint (oC) 80.5 A5 -
Octanol-water partition coefficient at pH 7, 20oC P 1.82 X 10-01 Calculated -
Log P -0.74 A5 Low
Bulk density (g ml-1)/Specific gravity 1.31 A5 -
Dissociation constant (pKa) at 25oC Not applicable A5 -
Note: Not determinable
Vapour pressure at 25oC (mPa) 2 A5 Volatile
Henry's law constant at 25oC (Pa m3 mol-1) 4.00 X 10-07 A5 Non-volatile
Henry's law constant at 20oC (dimensionless) 3.80 X 10-07 K3 Moderately volatile
GUS leaching potential index 0.00 Calculated Low leachability
SCI-GROW groundwater index (μg l-1) for a 1 kg ha-1 or 1 l ha-1 application rate Value 9.61 X 10-04 Calculated -
Note -
Potential for particle bound transport index - Calculated Low
Maximum UV-vis absorption L mol-1 cm-1 Maxima at 213nm = 1356 A5 -
Surface tension (mN m-1) 66.0 A5 -

Property Value Source/Quality Score/Other Information Interpretation
Soil degradation (days) (aerobic) DT50 (typical) 1 K4 Non-persistent
DT50 (lab at 20oC) 1 A5 Non-persistent
DT50 (field) 5 A5 Non-persistent
DT90 (lab at 20oC) 3.32 A5 -
DT90 (field) 2.66 A5 -
Note EU dossier Lab studies DT50 range 0.4-3.2 days, DT90 range 1.3-10.6 days at 25DegC; Field studies DT50 raneg 1.49-3.82 days, DT90 range 4.9-12.7 days
Plant matrix DT50 (days) Value 4.0 R3 -
Note Chilli, fruit surface matrix
Aqueous photolysis DT50 (days) at pH 7 Value 222 A5 Stable
Note Not significant route of degradation. DT50 187 days daylight, 257 days in dark, pH 5, 38 deg N, Spring
Aqueous hydrolysis DT50 (days) at 20oC and pH 7 Value 73 A5 Moderately persistent
Note pH sensitive: DT50 96.3 days at pH 5, 41 days at pH 7, 2.4 days at pH 4, all at 25 degC. 73 days at pH 7 and 20 degC
Water-sediment DT50 (days) 3 A5 Fast
Water phase only DT50 (days) 3 A5 Moderately fast

Soil adsorption and mobility:
Property Value Source/Quality Score/Other Information Interpretation
Linear Kd - DW4 Very mobile
Koc 10
Notes and range -
Freundlich Kf 0.36 A5 Mobile
Kfoc 29
1/n 0.928
Notes and range EU dossier Kf range 0.01-0.89 mL/g, kfoc range 2-58 mL/g, 1/n range 0.83-1.14, Soils=4
pH sensitivity No

Key metabolites:
Metabolite Formation medium Estimated maximum occurrence fraction 91/414 relevancy
2-ethylsulfinyl ethane sulfonic acid Soil   0.390   Major fraction, Relevant
2-ethylsulfonyl ethane sulfonic acid Soil   0.265   Major fraction, Relevant

Other known metabolites:
Metabolite name and reference Aliases Formation medium / Rate Estimated maximum occurrence fraction Metabolising enzymes
S-[2(ethylsulfonyl)ethyl]O,O-dimethylphoshorothioate demeton-S-methylsulphon; oxydemeton-methyl metabolite M01 Plant; Soil (Aerobic); Water/sediment - -
O-methyl-S-[2(ethylsulfinyl)ethyl] phoshorothioate oxydemeton-methyl metabolite M06 Plant; Water/sediment - -
O-methyl-S-[2(ethylsulfonyl)ethyl] phoshorothioate oxydemeton-methyl metabolite M07 Plant; Water/sediment - -
1-(ethylsulfonyl)-2-(methylsulfonyl) ethane oxydemeton-methyl metabolite M05 Soil (Aerobic) - -
dimethyl phosphate DMP Soil (Aerobic); Water - -
S-[2(ethylthio)ethyl]O,O-dimethylphoshorothioate. Pesticide common name: demeton-S-methyl oxydemeton-methyl metabolite M02 Water/sediment - -
2-ethylthio ethane sulfonic acid oxydemeton-methyl metabolite M22 Soil (Anaerobic) - -
bis-2-[(ethylsulfinyl)-ethyl]disulfide oxydemeton-methyl metabolite M11 Water/sediment - -
2-ethylsulfinyl-ethyl mercaptan oxydemeton-methyl metabolite M21 Water/sediment - -


for oxydemeton-methyl

Property Value Source/Quality Score/Other Information Interpretation
Bio-concentration factor BCF (l kg-1) Low risk A5 Based on LogP < 3 Low potential
CT50 (days) - -
Mammals - Acute oral LD50 (mg kg-1) 48 A5 Rat High
Mammals - Short term dietary NOEL (mg kg-1) 0.1 A4 Dog, 1 year High
(ppm diet) - -
Birds - Acute LD50 (mg kg-1) 34 A5 Colinus virginianus High
Birds - Short term dietary (LC50/LD50) 361 mg kg bw-1 day-1 A5 Colinus virginianus -
Fish - Acute 96 hour LC50 (mg l-1) 17 A5 Oncorhynchus mykiss Moderate
Fish - Chronic 21 day NOEC (mg l-1) 1.8 A5 Oncorhynchus mykiss Moderate
Aquatic invertebrates - Acute 48 hour EC50 (mg l-1) 0.11 A5 Daphnia magna Moderate
Aquatic invertebrates - Chronic 21 day NOEC (mg l-1) 0.027 A5 Daphnia magna Moderate
Aquatic crustaceans - Acute 96 hour LC50 (mg l-1) - - -
Sediment dwelling organisms - Acute 96 hour LC50 (mg l-1) 0.011 A4 Chironomus riparius, 48 hour High
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) - - -
Non-target plants - - -
- - -
Algae - Acute 72 hour EC50, growth (mg l-1) > 100 A5 Scenedemus subspicatus Low
Algae - Chronic 96 hour NOEC, growth (mg l-1) - - -
Honeybees Contact acute 48 hour LD50 (μg bee-1) 0.175 A5 High
Oral acute 48 hour LD50 (μg bee-1) 0.2 A5 High
Unknown mode acute 48 hour LD50 (μg bee-1) - - -
Earthworms - Acute 14 day LC50 (mg kg-1) 115 A5 Eisenia foetida Moderate
Earthworms - Chronic 14 day NOEC, reproduction (mg kg-1) 0.41 A4 Eisenia foetida Moderate
Other soil macro-organisms - e.g. Collembola LR50 / EC50 / NOEC / % Effect - - -
Other arthropod (1) LR50 g ha-1 >0.375 48 hour
A5 Aphidius rhopalosiphi
% Effect - - -
Other arthropod (2) LR50 g ha-1 11.0 7 day
A5 Typhlodromus pyri
% Effect - - -
Soil micro-organisms Nitrogen mineralisation: No significant adverse effect [Dose: 5 kg ha-1]
Carbon mineralisation: No significant adverse effect [Dose: 6 kg ha-1]
A5 -
Mesocosm study data NOEAEC mg l-1 - - -
NOEAEC mg l-1 - - -


for oxydemeton-methyl

Property Value Source/Quality Score/Other Information Interpretation
Threshold of Toxicological Concern (Cramer Class) High (class III) - -
Mammals - Acute oral LD50 (mg kg-1) 48 A5 Rat High
Mammals - Dermal LD50 (mg kg-1 body weight) 112 A5 Rat -
Mammals - Inhalation LC50 (mg l-1) 0.471 A5 Rat -
Other Mammal toxicity endpoints - -
ADI - Acceptable Daily Intake (mg kg-1bw day-1) 0.0003 A5 Rat, SF=100 -
ARfD - Acute Reference Dose (mg kg-1bw day-1) 0.0015 A5 Rat, SF=100 -
AOEL - Acceptable Operator Exposure Level - Systemic (mg kg-1bw day-1) 0.001 A5 Rat, SF=100 -
Dermal penetration studies (%) 20.0 A5 -
Dangerous Substances Directive 76/464 List II - -
Exposure Limits - - -
Exposure Routes Public Possible risk to bystanders
Occupational Possible exposure risk during treatment of orchards
European MRLs Click here for the EU MRL pesticide database
Drinking Water MAC (μg l-1) - - -

Health issues:
Carcinogen Mutagen Endocrine disrupter Reproduction / development effects Cholinesterase inhibitor Neurotoxicant


Respiratory tract irritant Skin irritant Skin sensitiser Eye irritant Phototoxicant




General human health issues Highly toxic

: Yes, known to cause a problem
: No, known not to cause a problem
: Possibly, status not identified
- : No data found

Handling issues:
Property Value Source/Quality Score/Other Information Interpretation
General Not explosive
IMDG Transport Code is usually 6.1
CLP classification 2013 Health: H301, H311
Environment: H400
EC Risk Classification T - Toxic: R24/25
N - Dangerous for the environment: R50
EC Safety Classification S1/2, S23, S36/37, S45, S61
WHO Classification Ib - Highly hazardous
US EPA Classification (formulation) No consensus across products or no products available - -
UN Number 3018
Waste disposal & packaging Packaging Group II (medium danger)


for oxydemeton-methyl

Language Name
English oxydemeton-methyl
French oxydemeton-methyle
German Oxydemeton-methyl
Danish oxydemeton-methyl
Italian ossidemeton-metil
Spanish oxidemeton metil
Greek oxydemeton-methyl
Slovenian oksidemeton metil
Polish oksydemeton metylu
Swedish -
Hungarian oxidemeton-methyl
Dutch oxydemeton-methyl

Record last updated: Sunday 14 August 2016