Oxydemeton-methyl in the product Metasystox R Systemic Insecticide

Foreword

The Australian Pesticides and Veterinary Medicines Authority (APVMA) is an independent statutory authority with responsibility for assessing and approving agricultural and veterinary chemical products prior to their sale and use in Australia.

In undertaking this task, the APVMA works in close cooperation with advisory agencies, including the Department of Health and Family Services (Therapeutic Goods Administration), Environment Australia (Risk Assessment and Policy Section), the National Occupational Health and Safety Commission (Worksafe Australia) and State departments of agriculture and environment.

The APVMA has a policy of encouraging openness and transparency in its activities and of seeking community involvement in decision making. Part of that process is the publication of public release summaries for all products containing new active ingredients and for all proposed extensions of use for existing products.

The information and technical data required by the APVMA to assess the safety of new chemical products and the methods of assessment must be undertaken according to accepted scientific principles.  Details are outlined in the APVMA's publications; Ag Manual:  The Requirements Manual for Agricultural Chemicals and Ag Requirements Series.

This Public Release Summary is intended as a brief overview of the assessment that has been completed by the APVMA and its advisory agencies.  It has been deliberately presented in a manner that is likely to be informative to the widest possible audience thereby encouraging public comment.

The APVMA welcomes comment on the usefulness of this publication and suggestions for further improvement.  Comments should be submitted to the Executive Manager-Registration, Australian Pesticides and Veterinary Medicines Authority, PO Box E240, Kingston ACT 2604.

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List of Abbreviations and Acronyms 

ac active constituent
ADI acceptable daily intake (for humans)
ai active ingredient
d Day
EbC50 concentration at which there is an effect on 50% of the biomass of an algae population
EC50 concentration at which 50% of the test population are immobilised
EUP end use product
h hour
ha hectare
HPLC high pressure liquid chromatography or high performance liquid chromatography
in vitro outside the living body and in an artificial environment
in vivo inside the living body of a plant or animal
kg kilogram
L litre
LC50 concentration that kills 50% of the test population of organisms
LD50 dosage of chemical that kills 50% of the test population of organisms
LOQ Limit of quantitation
mg milligram
mL millilitre
MRL Maximum Residue Limit
MSDS Material Safety Data Sheet
NDPSC National Drugs and Poisons Schedule Committee
ng nanogram
NOEC/NOEL no observable effect concentration/level
ppb parts per billion
PPE Personal Protective Equipment
ppm parts per million
s Second
SC suspension concentrate
SUSDP Standard for the Uniform Scheduling of Drugs and Poisons
T-Value a value used to determine the First Aid Instructions for chemical products that contain two or more poisons
TGAC technical grade active constituent
mg microgram
WDG water dispersible granule
WHP withholding period

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Summary

The Australian Pesticides and Veterinary Medicines Authority (APVMA) has considered an application to register the new chemical oxydemeton-methyl for the control of aphids in brassica vegetable crops, cotton (QLD, NSW and WA only) and lupins (NSW, VIC, SA and WA), as specified in the directions for use table on the products' labels (pp. 31 - 34).

This publication outlines the regulatory considerations and summarises the data reviewed by the APVMA for the proposed registration of oxydemeton-methyl.  Before deciding whether to approve this product for use in Australia, the APVMA invites public comment.  Comments should be submitted by 8 October 1999 to the APVMA at the address indicated on page 1.

The APVMA has assessed the data submitted by the applicant in support of this use of oxydemeton-methyl and provides the following information for public comment.

Public health aspects

The acute oral and dermal toxicity of oxydemeton-methyl is high (oral LD50 48 mg/kg and dermal LD50 112 mg/kg in rats).  Oxydemeton-methyl is a slight eye irritant in rabbits, and is not a skin sensitiser in guinea pigs.  The product, Metasystox R Systemic Insecticide containing 25% of oxydemeton-methyl, has moderate acute oral and dermal toxicity.  The product is a slight skin, and a moderate eye irritant in rabbits and is likely to cause skin sensitisation.

Oxydemeton-methyl is rapidly and extensively absorbed orally and rapidly excreted, primarily as the unchanged compound, in urine.  Significant tissue accumulation does not occur.

Oxydemeton-methyl is an organophosphorus compound.  Adverse clinical signs associated with exposure to chemicals of this class relate to the rapid decline in brain and blood cholinesterases (enzymes which break down the nerve signal transmitter acetyl choline and related compounds).  The result is accumulation of acetylcholine within the nervous system which leads to excessive nerve stimulation manifested as salivation, muscle tremors and depression.  Organ or tissue damage was not noted in repeat dose studies with oxydemeton-methyl.

Female fertility rates are reduced in rats when they are given high doses of oxydemeton-methyl.  In most studies, no adverse effects are reported on male reproduction, suggesting that the chemical may be acting primarily on female reproductive performance at high doses.  However in one study, male rats showed reduced sperm motility.  A consistent finding in males was microscopic change in the cells of the epididymides (vacuolation) which was seen after repeated exposure.  Male fertility was not affected, however.

Oxydemeton-methyl caused damage to genetic material in the majority of in vitro assays, and in mice given high doses of the chemical.  Other tests for DNA damage in vitro and in vivo  were negative.  Chromosome damage assays in animals were uniformly negative.  Tumour formation, in rats and mice, is not seen following administration of the compound for a lifetime.

Based on an assessment of the toxicology, it was considered that there should be no adverse effects on human health from the use of this product when used in accordance with the label directions.

Residues in food and trade aspects

Residues in food

Results from Brussels sprouts, cabbage, cauliflower, cotton, and lupin residue trials conducted in Australia allowed the establishment of oxydemeton-methyl MRLs for brassica vegetable crops, head cabbages, and flowerhead brassica, cotton seed, cotton seed oil (crude), and lupins (dry).  Overseas cotton data also supported the proposed cottonseed and oil MRLs.  Animal commodity MRLs for eggs, edible offal (mammalian), meat (mammalian), milks, edible poultry offal, and poultry meat were also established along with cotton and lupin forage MRLs.  When Metasystox R Systemic Insecticide is used to control aphids according to the proposed use patterns the recommended MRLs are not expected to be exceeded.

The residue definition is the sum of oxydemeton-methyl and demeton-S-methyl sulphone, expressed as oxydemeton-methyl.  This differs from the Codex Alimentarius oxydemeton-methyl residue definition of sum of oxydemeton-methyl, demeton-S-methyl and demeton-S-methylsulphone, expressed as oxydemeton-methyl.  The Australian residue definition is based on Good Agricultural Practice in Australia and the present analytical technology, which measures the oxydemeton-methyl as its sulphone derivative.  Residue data indicated that sulphone metabolite occurs in minor quantities.

Trade

The difference in the residue definition proposed in Australia and that of Codex should not adversely impact on trade.  The proposed residue definition in Australia for oxydemeton-methyl is not likely to result in violations of residues of demeton-S-methyl  and oxydemeton-methyl in countries that utilise the Codex definition for monitoring purposes.

There is always the likelihood that Australian traded commodities (containing residues of oxydemeton-methyl recommended in this report) may face trade barriers in countries that have not established MRLs for oxydemeton-methyl in certain of the commodities.   However there are expected to be no adverse effects on trade provided cognisance is taken of the requirements of importing countries.   Residues of oxydemeton-methyl in animal commodities in particular have not been identified as likely to adversely affect Australia's export trade.

Occupational health and safety aspects

NOHSC has conducted a risk assessment on Metasystox R Systemic Insecticide, containing oxydemeton-methyl at 250 g/L as an emulsifiable concentrate, for use on brassica vegetable crops, cotton and lupins crops.  Metasystox R Systemic Insecticide can be safely used by workers when handled in accordance with the control measures indicated in this assessment.

Oxydemeton-methyl is not currently on the National Occupational Health and Safety Commission (NOHSC) List of Designated Hazardous Substances.  Bayer Australia Limited has determined oxydemeton-methyl to be a hazardous substance based on acute toxicity.  Bayer Australia Limited has also determined Metasystox R Systemic Insecticide to be a hazardous substance accordingly with NOHSC criteria (acute toxicity).  The product will be formulated in Australia from imported technical grade manufacturing concentrate, containing 50% oxydemeton-methyl and 50% monochlorobenzol.  Monochlorobenzol is on the NOHSC List of Designated Hazardous Substances.  Australian workers can be exposed to the manufacturing concentrate and end use product (EUP) during formulation and packaging.  Workers involved in transport, storing and retailing can only be exposed if packaging is breached. Engineering controls, biological monitoring and training to protect the production and maintenance personnel are the responsibility of the manufacturers.

The EUP demonstrated moderate oral and dermal acute toxicity. The oral LD50 was 144 mg/kg in male rats and 135 mg/kg in female rats.  The dermal LD50 was 299 mg/kg in male and 116 mg/kg in female rats.  The formulation was a slight dermal, and a moderate eye irritant in rabbits. The product is likely to have dermal sensitisation potential.  The manufacturing concentrate has a moderate acute inhalation toxicity.  It is also a dermal sensitising agent in guinea pigs.

Formulators and packers should wear appropriate protective equipment such as overalls, gloves and full face respirators.  Advice on safe handling of the manufacturing concentrate and end use product (EUP) during routine formulation and end use is provided in the material safety data sheets (MSDS).

 The EUP is to be diluted with water and applied by ground or aerial spray. The risk assessment indicates that chemical resistant clothing, elbow-length PVC gloves, impervious footwear and full face respirator with combined dust and gas cartridge are required when opening the container and preparing spray.  Water proof clothing, cotton overalls, elbow-length PVC gloves, impervious footwear and face shield or goggles are recommended when using the prepared spray.

Environment aspects

Environmental exposure to oxydemeton-methyl will principally involve the soil, waterways and other non-target areas effected due to runoff or spray drift.  Degradation of oxydemeton-methyl occurs rapidly in soils and aquatic systems, with half-lives of a few days.  While oxydemeton-methyl was weakly adsorbed to a range of soils and the leaching studies showed it could be mobile, the semi-field studies did not show any leaching, mainly due to the rapid degradation in soil.  Accumulation and bioaccumulation are also considered unlikely.

The ecotoxicological profile of oxydemeton-methyl indicates high to moderate toxicity to birds, moderate toxicity to mammals, moderate toxicity to fish and very high toxicity to aquatic invertebrates.  It is also highly toxic to bees.  Phytotoxicity is low.

Oxydemeton-methyl has very limited persistence in the environment and represents a low hazard to most non-target organisms under the proposed conditions of use.  The hazard from the proposed uses was calculated to be low for mammals and birds but high to bees and possibly other non-target terrestrial insects.  The hazard to earthworms was considered low.

For aerial applications, apart from direct overspray, the hazard to fish was considered to be low.  The hazard to daphnia and other aquatic invertebrates, the most sensitive organisms, was considered to be low and acceptable when used according to best agricultural guidelines, i.e. the new Best Management Practice Manual for Cotton Growers.  Aerial application to cotton and lupins is supported provided application methods are use to limit the impact of spray drift.  Such a strategy is exemplified in the Best Management Practice Manual for Cotton and Operation Spray Safe: Pilots and Operators Manual.

Calculations clearly show that the spray drift hazard from boomsprayers poses a low hazard to aquatic invertebrates near to the spray operations.  The application of oxydemeton-methyl by boom sprayers in brassica vegetable crops, lupins and in cotton is supported.

Runoff from treated areas was not considered a hazard to aquatic invertebrates, based on the aquatic organisms tested.

Efficacy and phytotoxicity aspects

Oxydemeton-methyl is proposed to be used by ground rig or by air to control aphid pests of brassica vegetable crops, cotton (NSW, QLD, NT and WA only) and lupins (NSW, VIC, SA and WA only).

The rate of use varies between crops; 1.1 L/ha for brassica vegetable crops; 300 mL/ha for cotton; and 300 mL/ha or 560 mL/ha for lupins, depending on aphid pest being controlled.  The maximum number of applications proposed per season are 3 for brassica vegetable crops, 2 for cotton and 1 for lupins.

Data presented by Bayer Australia Limited supported claims that Metasystox R Systemic Insecticide adequately control aphids in brassica vegetable crops, cotton and lupins.  The data were gathered from a range of replicated and unreplicated trials.

The data were adequate to satisfactorily assess efficacy when used according to the label directions.

All trials reported no observed phytoxicity from the application of Metasystox R Systemic Insecticide to brassica vegetable crops, cotton or lupins.

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Introduction

This publication provides a summary of the data reviewed and an outline of the regulatory considerations for the proposed application of the chemical oxydemeton-methyl as an insecticide for the control of aphids in brassica vegetable crops, cotton and lupins.  It also seeks public comment prior to the chemical product being approved for use in Australia.

Responses to public consultation will be considered prior to registration of the products detailed in this document.  They will be taken into account by the APVMA in deciding whether the product should be registered and in determining appropriate conditions of registration and product labeling.

Copies of full technical reports on occupational health and safety aspects, environmental impact, and residues in food are available from the APVMA on request.

Written comments should be received by the APVMA by 5 October 1999, and be sent to:

Mr Graeme Barden

Senior Product Evaluator

Agricultural Chemicals Registration

National Registration Authority

PO Box E240

KINGSTON ACT 2604

FAX: 02 6272 3218

Applicant

Bayer Australia Limited has applied for registration of an insecticide product containing a new active constituent, oxydemeton-methyl, a metabolite of a previously approved active constituent, demeton-S-methyl.

Product details

Oxydemeton-methyl will be marketed under the trade name Metasystox R Systemic Insecticide , an emulsifiable concentrate product containing 250 g/L oxydemeton-methyl.

Metasystox R Systemic Insecticide will be formulated and packed inside Australia.

Bayer Australia Limited intends to market Metasystox R Systemic Insecticide for the control of aphids in brassica vegetable crops, cotton (NSW, QLD, NT and WA only) and lupins (NSW, SA, VIC and WA only).

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Chemistry and Manufacture

Active constituent

The chemical active constituent oxydemeton-methyl has the following properties:

Common name (ISO): oxydemeton-methyl
Chemical name: S-2-(ethylsulfinylethyl O,O-dimethyl) phosphorothioate
CAS Registry Number: 301-12-2
Empirical formula:    C6H15O4PS2
Molecular weight: 246.3
Physical form: liquid
Colour: colourless
Odour: odourless
Melting point: < -20C
Boiling point: >80C at 1013 mmHg 106C at 0.013 mmHg
Specific gravity: 1.29 at 20C
Octanol/water partition coefficient (Kow): 0.18
Vapour pressure at 20C:   3.8 x 10-5 mmHg
Structural formula:

Structural formula

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Toxicological Assessment

The toxicological database for oxydemeton-methyl, which consists primarily of toxicity tests conducted using animals, is quite considerable.  In interpreting the data, it should be noted that toxicity tests generally use doses which are high compared to likely human exposures.  The use of high doses increases the likelihood that potentially significant toxic effects will be identified.  Toxicity tests should also indicate dose levels at which the specific toxic effects are unlikely to occur.  Such dose levels as the No Observable Effect Level (NOEL) are used to develop acceptable limits for dietary or other intakes at which no adverse health effects in humans would be expected.

Toxicokinetics and metabolism

Oxydemeton-methyl is rapidly and extensively absorbed after oral administration to rats and rapidly eliminated almost entirely in the urine primarily as the unchanged compound (65%) with the balance metabolised to various compounds.  Skin application to rats results in absorption of approximately 50% of the applied dose with peak blood levels occurring within 4 hours.  In Rhesus monkeys skin absorption was more limited with 20-30% of the dose excreted in the urine over 14 days following application.  There was no evidence of tissue accumulation.

Acute studies

Oxydemeton-methyl has high acute oral (LD50 = 48 mg/kg) and moderate dermal toxicity in rats (LD50 = 112 mg/kg) and moderate oral toxicity in guinea pigs (LD50 = 120 mg/kg).  Oxydemeton-methyl is a slight ocular irritant in rabbits, and does not cause dermal sensitisation in guinea pigs.

The product, Metasystox R Systemic Insecticide has moderate oral (LD50 = 135 mg/kg) and dermal (LD50 = 116 mg/kg) acute toxicity in rats, is a slight skin, and a moderate eye irritant in rabbits and is likely to have dermal sensitisation potential due to a non active constituent of the formulation.

Short-term studies

Oxydemeton-methyl given orally to rats at 0.15, 0.45 or 2.5 mg/kg/day for 14 days decreased brain cholinesterase activity in all animals and plasma, red blood cell (RBC) and brain cholinesterase activity in all except the males at 0.15 mg/kg/day.  In a second oral study in rats at doses of 0, 0.3, 0.9 or 5 mg/kg/day of a 50% oxydemeton-methyl preparation for 14 days, males at 0.9 and 5 mg/kg/day gained less weight.  Brain, plasma and RBC cholinesterase activity was depressed in all treated female groups.  In males cholinesterase was inhibited in the brain at all doses and in plasma and red blood cells at 0.9 mg/kg bw/day and above.  Dermal application of 0.3, 1 or 5 mg/kg/day oxydemeton-methyl for 14 days produced similar effects with reduced plasma, RBC and brain cholinesterase levels at 5 mg/kg/day and RBC cholinesterase in females at 1 mg/kg/day.  Brain cholinesterase activity was decreased in males at 1 and 5 mg/kg/day, and in females at all doses.  In a 3 week inhalation study no significant effects were noted in rats at up to 7.8 mg/m3.

Skin application of oxydemeton-methyl to rabbits at 0, 0.3, 1.8 or 10.8 mg/kg for 6 hours produced no observable effects.  In a second study, application for 6 hours at 0, 2 or 20 mg/kg reducing to 0, 0.5 or 5 mg/kg after 2 days, for 21 days, produced slight muscle tremors at 2 or 20 mg/kg after 2 days which resolved when the doses were reduced. RBC cholinesterase in both sexes and brain cholinesterase levels in females were reduced at 5 or 20 mg/kg/day.

Longer term studies

Mice fed 0, 0.45, 2.25 or 7.5 mg/kg/day of oxydemeton-methyl for 21 months had reduced activity, convulsions, urine straining and rough coats at 7.5 mg/kg/day.  Males at 7.5 mg/kg/day gained less weight and treated females ate less.  Plasma cholinesterase was reduced in treated females and in males at 2.25 and 7.5 mg/kg/day.  RBC cholinesterase was reduced at 2.25 and 7.5 mg/kg/day and brain cholinesterase at all doses.  Microscopic changes to the epididymides (cytoplasmic vacuolations) were seen in males at 2.25 and 7.5 mg/kg/day.  A NOEL was not achieved.

Oral oxydemeton-methyl at 2.5 and 12.5 mg/kg/day in rats for 3 months reduced plasma and RBC cholinesterase activity.  At 2.5 and 12.5 mg/kg/day animals ate less and gained less weight.  In a second 3-month study, rats fed up to 10.0 mg/kg/day ate less, had increased plasma enzyme levels and slight changes to plasma protein concentrations at 10 mg/kg/day.  Cholinesterase activity was reduced at 1.0 and 10.0 mg/kg/day.  In a 2 year study rats given up to 5 mg/kg/day ate less and gained less weight at 5 mg/kg/day, plasma and RBC cholinesterase were reduced at 0.5 and 5 mg/kg/day, and male liver weights were decreased at 5 mg/kg/day.  A general loss of condition and  skin inflammation and ulceration were seen at 5 mg/kg/day.  The NOEL across these three studies was 0.027 mg/kg/day.

Oxydemeton-methyl in dogs at up to 2.5 mg/kg/day orally for 12 months caused inhibition of cholinesterase in plasma, brain and RBC at 2.5 mg/kg/day only.  The NOEL was 0.25 mg/kg/day.

Carcinogenicity

Oxydemeton-methyl fed to mice for up to 24 months at up to 15 mg/kg/day, or to rats for 2 years at up to 5 mg/kg/day did not increase the normal background incidences of cancer in these species.

Reproduction and developmental studies

In pregnant rats treated with 3 mg/kg/day of oxydemeton-methyl during the period of foetal organ formation, a delayed foetal development was observed, which may have been due to maternal toxicity.  In a second study, there were no effects on the foetus or embryo at up to 4.5 mg/kg/day.  Dams at 1.5 and 4.5 mg/kg/day ate less and gained less weight and had decreased cholinesterase activity.  The NOEL across both studies was 1 mg/kg/day.   Similarly in rabbits given  up to 1.6 mg/kg/day, maternal toxicity was noted at 1.6 mg/kg/day with depressed cholinesterase activity, and loose stools but the foetuses were unaffected.  The NOEL was 0.4 mg/kg/day in rabbits.

Oxydemeton-methyl administered to three successive generations of rats at up to 2.5 mg/kg/day resulted in a decreased pregnancy rate, decreased number of pups per litter and decreased RBC cholinesterase activity in some generations at 1.25 and 2.5 mg/kg/day.  The NOEL was 0.5 mg/kg/day.

Oxydemeton-methyl administered to 2 successive generations of rats at 2.5 mg/kg/day, reduced fertility, pup survival after birth and lactation in the dams.  Smaller litters were seen at 0.5 and 2.5 mg/kg/day.  Animals at less and gained less weight at 2.5 mg/kg/day, and gained less weight at 0.5 mg/kg/day.  Microscopic changes to the epididymides (vacuolation) was increased in males at 2.5 mg/kg/day and one male at 0.5 mg/kg/day.  The NOEL was 0.05 mg/kg/day.

A study across two successive generations of rats fed 50% oxydemeton-methyl (in methyl isobutyl ketone) at levels equivalent to 0, 0.05, 0.15, 0.45 or 2.5 mg/kg bw/day of oxydemeton-methyl, or 2.5 mg/kg/day of oxydemeton-methyl, produced lower weight gains in females during gestation, and fertility was reduced (percentage of sperm positive females which delivered) at 2.5 mg/kg/day of either preparation.  Decreased or absent corpora lutea, and a reduction in the number of uterine implantation sites were noted at 2.5 mg/kg/day of oxydemeton-methyl.  Litter size and pup viability were reduced, and pups gained less weight during the lactation period at 2.5 mg/kg/day of either preparation.  Pup plasma and brain cholinesterase activity were reduced at 0.45 mg/kg bw/day, and RBC cholinesterase activity was lower at 2.5 mg/kg/day of either preparation, and rarely at 0.45 mg/kg/day.  Brain and RBC cholinesterase activities were reduced in adults at all doses and plasma cholinesterase activity was reduced above 0.05 mg/kg/day.  A NOEL for maternal toxicity was not achieved. The NOEL for pup toxicity was 3 ppm of 50% oxydemeton-methyl.

A number of studies were conducted on male rats at up to 5 mg/kg/day of oxydemeton-methyl to investigate the apparent epididymal effects seen in a reproduction study.  In one study, male rats were given 0, 0.15, 0.9 or 5.0 mg of oxydemeton-methyl/kg/day orally for 5 days and then mated repeatedly on days 1, 7, 14, 21, 35, 56 and 112 after the final dose.  Males at 0.9 and 5.0 mg/kg/day had reduced sperm motility but fertility was unaffected.  In two subsequent studies using oral doses of up to 5 mg/kg/day for up to 3 months sperm motility was unaffected.  Microscopic epididymal changes (vacuolations) were seen at doses of 0.9 mg/kg/day and above.  In a study using a dose of 5 mg/kg/day for 10 weeks fertility was again unaffected.

Male rats were fed 0, 0.15, 0.45 and 2.5 mg/kg/day of oxydemeton-methyl for 8 months.  Microscopically, the epididymal vacuoles at 0.45 and 2.5 mg/kg/day were variable sized, membrane bound cytoplasmic bodies.  The content was concluded to be proteinaceous in nature.

Genotoxicity

Oxydemeton-methyl caused mutation in some assays using microorganisms in vitro and at high doses in insects and mice.  Also, damage to genetic material was noted in cultured mammalian cells.  On the other hand, negative effects were obtained in mutation assays in bacteria and cultured mammalian cells.  Tests for DNA damage in vitro and in vivo  and chromosome damage studies in vivo  were negative.  The weight of evidence indicates no genotoxic potential in vivo .

Public health standards

Poisons Scheduling

The National Drugs and Poisons Schedule Committee (NDPSC) considered the toxicity of the product and its active ingredients and assessed the necessary controls to be implemented under States' poisons regulations to prevent the occurrence of poisoning.  The NDPSC recommended that oxydemeton-methyl be listed in Schedule 7 of the Standard for the Uniform Scheduling of Drugs and Poisons (SUSDP).  There are provisions for appropriately stringent warning statements and first aid directions on the product label, in recognition of the relatively high toxicity of oxydemeton-methyl.

NOEL/ADI

Rats were the most sensitive species, with a NOEL of 0.027 mg/kg/day.  In order to calculate the acceptable daily intake (ADI) for humans, a safety factor is applied to the NOEL in the most sensitive species.  The magnitude of the safety factor is selected to account for uncertainties in extrapolation of animal data to humans; variation within the human population; the quality of the experimental data; and the nature of the potential hazards.  Using a safety factor of 100 an ADI of 0.0003 mg/kg/day for oxydemeton-methyl was established.

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Residues Assessment

Bayer Australia Limited has made a submission to the National Registration Authority in support of  registration of an end-use product containing oxydemeton-methyl (Metasystox R Systemic Insecticide (250 g/L EC)) for control of aphids on brassica vegetable crops, cotton, and lupins and establishment of maximum residue limits for oxydemeton-methyl in brassica vegetable crops, cotton, lupins and animal commodities.

The active ingredient in Metasystox R is oxydemeton-methyl, the main plant metabolite of demeton-S-methyl.  Demeton-S-methyl was the active ingredient in Metasystox (I) Systemic Insecticide. Metasystox (I) is no longer registered, and demeton-S-methyl is no longer an approved active.  Oxydemeton-methyl residues are currently included under the demeton-S-methyl residue definition as demeton-S-sulfoxides.  This is because oxydemeton-methyl is a major plant metabolite of demeton-S-methyl.

The ADI for oxydemeton-methyl as set by the Therapeutic Goods Administration (TGA) of the Department of Health and Family Services is 0.0003 mg/kg/day.  The ADI is based on the parent compound only and does not include any metabolites such as demeton-S-methyl sulphone.

Methods of Residue Analysis

The method of residue analyses involves solvent extraction of residues followed by oxidation of the extract to furnish demeton-S-methyl sulphone.  The final extract is analysed via gas-chromatography equipped with a thermionic detector (AFID).  The recoveries were within acceptable ranges of 80 - 100% with the limit of sensitivity of at least 0.01 ppm.

Recommended MRLs

A total of seven residue trials have been conducted on brassica vegetable crops, five trials on cotton and three trials on lupins.  In addition, results of six other cotton trials conducted in USA have been submitted.

Cottonseed

Based on the proposed use pattern of Metasystox R in cotton, oxydemeton-methyl or its metabolite demeton-S-methyl sulphone was not detected in cottonseeds at the Limit of Quantitation of 0.01 mg/kg.  Based on the Australian residue definition for oxydemeton-methyl which includes the sum of oxydemeton-methyl and demeton-S-methyl sulphone expressed as oxydemeton-methyl, the MRL in Australia has been proposed at *0.01 mg/kg.

Cottonseed oil, crude

Processing studies with cottonseeds have indicated that oxydemeton-methyl or its metabolite demeton-S-methyl sulphone (per the Australian residue definition) does not concentrate in crude cottonseed oil. Based on the Australian residue definition for oxydemeton-methyl which includes the sum of oxydemeton-methyl and its metabolite demeton-S-methyl sulphone expressed as oxydemeton-methyl, the MRL for cotton seed oil, crude in Australia has been proposed at *0.01 mg/kg.

Brassica

Based on the proposed use pattern of Metasystox R in brassica vegetable crops, the highest quantifiable residue of oxydemeton-methyl or its metabolite demeton-S-methyl sulphone detected in brassicas was 0.31 mg/kg.  Based on the Australian residue definition for oxydemeton-methyl which includes the sum of oxydemeton-methyl and demeton-S-methyl sulphone expressed as oxydemeton-methyl, the group MRL in Australia has been proposed at 0.5 mg/kg.

Lupins

Based on the proposed use pattern of Metasystox R in lupins, oxydemeton-methyl or its metabolite demeton-S-methyl sulphone was not detected in lupins at the Limit of Quantitation of 0.01mg/kg.  Based on the Australian residue definition for oxydemeton-methyl which includes the sum of oxydemeton-methyl and demeton-S-methyl sulphone expressed as oxydemeton-methyl, the MRL in Australia has been proposed at *0.01 mg/kg.

Edible offal (mammalian) and Meat [mammalian]

The MRL for edible offal (mammalian) is based on the likelihood of livestock consuming finite levels of at the most 1ppm oxydemeton-methyl through animal feeds, (the highest level for animal feed commodities in this submission is 1 mg/kg).  In the lactating cow study, the lowest dose of oxydemeton-methyl fed to animals for 28 days was 10 ppm.  At this dose, no residues in any tissue (liver, kidney, fat or muscle) or milk were found above the Limit of Quantitation of the analytical method of 0.01 mg/kg.  Metabolism studies in rodents indicate that oxydemeton-methyl is rapidly absorbed from the gastrointestinal tract  within 2 hours of ingestion.  Most of the oxydemeton-methyl absorbed is excreted, unchanged, in the urine within 24 hours, with little tissue accumulation occurring.  The lactating goat data also provide assurance that the proposed MRLs are compatible with all species.  In the absence of metabolism studies in pigs, the feeding studies in rodents can be used to allow consideration of a mammalian set of MRLs.

Based on the study in lactating cows, an MRL of  *0.01 mg/kg for oxydemeton-methyl individually in edible offal (mammalian) and in meat [mammalian] is proposed.

Milks

The MRL for milks is based on the likelihood of livestock consuming finite levels of at the most 1 ppm oxydemeton-methyl through animal feeds such as cotton and lupin forage.  Although a Table 4 entry has been set for cotton forage, it is recognised that cotton forage is not often fed to animals.  The other feed commodity is lupin forage for which a Table 4 entry of 0.01 ppm has been proposed.  In the lactating cow study, the lowest dose of oxydemeton-methyl fed to animals for 28 days was 10 ppm.  At this dose, no residues in milk were found above the Limit of Quantitation of the analytical method of 0.01 mg/kg.

The feeding studies in the lactating cow (as goats milk is not widely consumed or traded), has been considered in establishing the Australian MRL.  An MRL of *0.01 mg/kg for oxydemeton-methyl in milk is proposed.

Poultry meat

The MRL for poultry meat is based on the likelihood of poultry consuming finite levels of 0.01 ppm oxydemeton-methyl through consumption of commodities such as lupin grain, forage and cotton seeds containing 0.01 mg/kg oxydemeton-methyl, the highest level anticipated in feed commodities.  In the hen study, the lowest dose of oxydemeton-methyl fed to hens for 28 days was 0.65 ppm .  At this dose, the highest total quantifiable residues in muscle were below the limit of  quantitation of  0.01 mg/kg.

Based on the study, an MRL of *0.01 mg/kg for oxydemeton-methyl in poultry meat is proposed.

Poultry, edible offal of

The MRL for edible offal of poultry is based on the likelihood of poultry consuming finite levels of 0.01 ppm oxydemeton-methyl through consumption of commodities such as lupin grain, forage and cotton seeds containing 0.01 mg/kg oxydemeton-methyl, the highest level anticipated in feed commodities. In the hen study, the lowest dose of oxydemeton-methyl fed to hens for 28 days was 0.65 ppm .  At this dose, the highest total quantifiable residues in offal were below the limit of  quantitation of 0.01 mg/kg.

Based on the study, an MRL of *0.01 mg/kg for oxydemeton-methyl in edible offal of poultry is proposed.

Eggs

The MRL for eggs of poultry is based on the likelihood of poultry consuming finite levels of 0.01 ppm oxydemeton-methyl through consumption of commodities such as lupin grain, forage and cotton seeds containing 0.01 mg/kg oxydemeton-methyl, the highest level anticipated in feed commodities. In the hen study, the lowest dose of oxydemeton-methyl fed to hens for 28 days was 0.65 ppm .  At this dose, the highest total quantifiable residues in eggs were below the limit of  quantitation of 0.01 mg/kg.

Based on the study, an MRL of *0.01 mg/kg for oxydemeton-methyl in eggs is proposed.

Residues in food in commerce or at consumption

Residues in crop treated with Metasystox R are low at the time of harvest due to the high degradation rate of oxydemeton-methyl.  Based on the low level of oxydemeton-methyl residues occurring in crops for human consumption, oxydemeton-methyl does not pose any significant risk to the consumers of treated crops.

Residues in cotton and the cotton processing study showed that there is no concentration in the oil fraction.

Lupin grains may be consumed by humans.  Residue data included in the submission clearly demonstrated that there are no quantifiable residues in the lupin grain 42 days after application.  Therefore, it can be concluded that the consumption of Metasystox R treated lupin grain will not pose any risk to consumers.

Residues in mammalian and poultry meat and offal, milk and eggs were also below the Limit of Quantitation.  As a result, the potential for intake following consumption of these commodities is low.

Dietary risk assessment

The hypothetical Theoretical Maximum Daily Intake (TMDI) is estimated to be equivalent to approximately 120 % of the ADI.  Based on the use of the Supervised Trial Median Residue (STMR) for brassica vegetable crops, the hypothetical estimated intake of oxydemeton-methyl is approximately 47% of the ADI.  The National estimated daily intake using Australian consumption values where available is 133% of the ADI.  However, when STMR values are used, the intake is 60% of the ADI.  Given the overestimation associated with the TMDI calculation, the dietary intake is expected to be below the ADI when all the overestimates allowed in the TMDI calculation are discounted.  The intake value from the STMR calculation supports this position.

Residue definition

The following residue definition is recommended for oxydemeton-methyl, to be included in Table 3 of the MRL Standard.  The residue definition is based on the metabolic profile of oxydemeton-methyl and Good Agricultural Practices (GAP) in Australia.

Oxydemeton-methyl Sum of oxydemeton-methyl and demeton-S-methyl sulphone, expressed as oxydemeton-methyl

Demeton-S-methyl has not been included in the residue definition because it is not a metabolite of oxydemeton-methyl and the sponsor has not renewed registration of Metasystox (I).  In Australia, there are no other registrants of demeton-S-methyl, and as such there is little potential for residues of demeton-S-methyl in treated crops.  However, following non-renewal of product, the sponsor has two years for product already existing in the marketplace to be used, following which all unused product will need to be recalled.  This two year period will end on 30 June 2000, so there will be a short period of time where both demeton-S-methyl and oxydemeton-methyl may be used in the marketplace.  However, the potential for this to adversely affect trade or impact adversely on consumer health and safety or lead to violations of MRLs is anticipated to be low.  This is because demeton-S-methyl and oxydemeton-methyl should not be used together.  That is, farmers will either use demeton-S-methyl or oxydemeton-methyl, and this is in agreement with the label directions on which the current MRLs for demeton-S-methyl and proposed MRLs for oxydemeton-methyl have been set.  Furthermore, the magnitude of the MRLs are the same for demeton-S-methyl and oxydemeton-methyl.

It should be recognised that the residue definition proposed in Australia is different to that set by Codex which takes into account the presence of demeton-S-methyl, primarily because Codex have set their residue definition to take into account the possible use of demeton-S-methyl and oxydemeton-methyl.  This however will not be the case in Australia because demeton-S-methyl has been withdrawn from the marketplace.

The residue definition recommended for oxydemeton-methyl is based on GAP in Australia and the present analytical technology available to monitor for residues.  The only current analytical technique available employs an oxidation step, which converts the oxydemeton-methyl to the demeton-S-methyl sulphone before measurement of the analyte as the sulphone derivative.  As a result, it is necessary to take into account the sulphone metabolite which is formed in minor quantities and which otherwise may not necessarily have been included in the residue definition.

Bioaccumulation

It has been established in evaluations conducted by the APVMA, that oxydemeton-methyl is not a potential bioaccumulator.  The log of the octanol/water partition coefficient (log Pow) = -0.74.

MRL Standard

The following additions to the MRL Standard are recommended for oxydemeton-methyl:

Table 4

Group Animal Feed Commodity MRL (mg/kg)
AV 0691 Cotton forage 1
AL 0545 Lupin forage *0.01

* Level at or about the Limit Of Quantitation (LOQ)

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Assessment of Overseas Trade Aspects of Residues in Food

Treated commodities

The difference in the residue definition proposed in Australia and that of Codex should not adversely impact on trade.  The proposed residue definition in Australia for oxydemeton-methyl is not likely to result in violations of residues of demeton-S-methyl (as MRLs for demeton-S-methyl are applicable until 30 June 2000) and oxydemeton-methyl in countries that utilise the Codex definition for monitoring purposes.

There is always the possibility that Australian traded commodities (containing residues of oxydemeton-methyl recommended in this report) may face trade barriers in countries that have not established MRLs for oxydemeton-methyl in certain of the commodities (e.g., Japan does not set MRLs in meat).  No adverse effects on trade (other than those identified in this report) are envisaged from the proposed uses of oxydemeton-methyl.

Cottonseed oil and meal are minor export items. The residue results presented show that at the rates of use the levels of residues will be at or below the LOQ in cottonseed. There is no concentration in the oil fraction.

No MRLs have been established in the countries to which Australia exports cauliflowers.  Even though the MRL in Australia for brassica vegetable crops (including cauliflowers) is set at 0.5 mg/kg, the actual residues are expected to be in the range of <LOQ to 0.25 mg/kg.  As a result, no impact with respect to exports to the United Kingdom is expected.  The United Kingdom MRL is 0.4 mg/kg.  With respect to some other countries, there is a possibility that Australian cauliflowers may face trade barriers, especially since the Codex MRLs are lower than the proposed Australian MRLs.

MRLs have not been established in the other countries to which Australia exports lupins.  However, it should be noted that the MRL in Australia is at or about the Limit of Quantitation, and therefore, that negligible impact on trade is expected.

Animal and Poultry Commodities

Edible offal [mammalian] and meat [mammalian]

While an Australian MRL of *0.01 mg/kg has been recommended, this MRL has been based on a feeding study where 10 ppm were fed to lactating cows.  The level of oxydemeton-methyl in Australian animal feed commodities is most likely to be *0.01 mg/kg, since cotton forage is not used often as a stockfeed.  The residue levels in animal feed commodities is substantially lower than the level of 10 or 30 ppm in the feeding study used as a basis to establish the Australian MRL.  It should also be noted that neither of the animal feed commodities is fed to animals at 100% of the animal feed.  Based on the above, the residue of oxydemeton-methyl in mammalian edible offal or mammalian meat is unlikely to exceed 0.01 mg/kg, and as a result, the proposed MRLs are highly unlikely to affect trade of mammalian offal and meat between Australia and its major exporting countries.

Milks

Milk in the form of whole milk powder is exported mainly to Malaysia and Taiwan.  Cheese is exported mainly to Japan and Saudi Arabia.  Butter and butterfat is exported mainly to Thailand and Singapore.  Skim milk powder is exported mainly to Philippines and Malaysia.  Neither of these countries has established MRLs for oxydemeton-methyl.  The Australian MRL of *0.01 mg/kg (i.e., at or about the LOQ) is not likely to adversely affect trade between Australia and countries to which Australia exports milk products.

Poultry and poultry by-products

Australia is not a major exporter of poultry meat, offal or eggs.  Not withstanding this, it should be noted that the proposed Australian MRLs for oxydemeton-methyl based on the proposed uses are at or below those recommended by Codex or those established in some other countries.  As a result, these MRLs are not expected to adversely affect trade.

Proposed Maximum Residue Limits and Withholding Periods

Proposed MRLs

On the basis of the data on residues from supervised trials, the following MRLs are proposed for oxydemeton-methyl.

Table 1
Group Food MRL (mg/kg)
VB 040 Brassica (cole or cabbage) vegetables, Head cabbages, Flowerhead brassica 0.5
SO 0691 Cotton seed *0.01
OC 0691 Cotton seed oil, crude *0.01
SO 0495 Canola (rape seed) *0.01
PE 0112 Eggs *0.01
MO 0105 Edible offal (mammalian) *0.01
VD 545 Lupins (dry) *0.01
MM 0095 Meat (mammalian) *0.01
ML 0106 Milks *0.01
PO 0111 Poultry, edible offal of *0.01
PM 0110 Poultry meat *0.01
Table 4
Group Animal Feed Commodity MRL (mg/kg)
AV 0691 Cotton forage 1
AL0545 Lupin forage *0.01

* Level at or about the Limit Of Quantitation (LOQ)

Proposed Withholding Periods

On the basis of the data on residues from supervised trials, the following WHPs are proposed for oxydemeton-methyl as Metasystox R Systemic Insecticide.

Crop Withholding period
Grazing Harvest
Brassica vegetable crops Do not graze 14 days
Cotton seed 21 days 21 days
Lupins 6 weeks 6 weeks

The following restraints will appear on the label:

HARVEST

BRASSICAS: DO NOT HARVEST FOR 14 DAYS AFTER APPLICATION

COTTON: DO NOT HARVEST FOR 21 DAYS AFTER APPLICATION

LUPINS:   DO NOT HARVEST FOR 6 WEEKS AFTER APPLICATION

GRAZING

BRASSICAS: DO NOT GRAZE ANY TREATED AREA OR CUT FOR STOCK FOOD

COTTON: DO NOT GRAZE OR CUT FOR STOCK FOOD FOR 21 DAYS AFTER

  APPLICATION

LUPINS:   DO NOT GRAZE OR CUT FOR STOCK FOOD FOR 6 WEEKS AFTER

  APPLICATION

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Occupational Health and Safety Assessment

Oxydemeton-methyl is not currently listed as a hazardous substance in the draft National Occupational Health and Safety Commission (NOHSC) List of Designated Hazardous Substances.  Bayer Australia Limited has determined oxydemeton-methyl to be a hazardous substance according to NOHSC criteria, based on acute toxicity.

The following risk and safety phrases are allocated to oxydemeton-methyl:

R24   Toxic in contact with skin

R25   Toxic if swallowed

Substances are hazardous when they contain concentrations of ≥3% oxydemeton-methyl.  Oxydemeton-methyl is a light brown liquid with a mercaptan smell.  In experimental animals (rats), oxydemeton-methyl had moderate to high oral, and high dermal acute toxicity.  Oral LD50 values were 61 and 48 mg/kg in male and female rats, respectively.  The dermal LD50 were 152 and 112 mg/kg in male and female rats, respectively.  Oxydemeton-methyl was a slight ocular irritant in rabbits, and did not cause dermal sensitisation in guinea pigs.  Data on inhalation toxicity is not available.

The technical grade manufacturing concentrate contains 50% oxydemeton-methyl and 50% monochlorobenzol.  Monochlorobenzol is on the NOHSC List of Designated Hazardous Substances.  It is harmful at concentrations ≥ 5%.  Above 5%, it is to be classified as R20 and/or R21 and/or R22.

Bayer Australia has classified the technical grade manufacturing concentrate as a hazardous substance according to NOHSC Approved Criteria for Classifying Hazardous Substances based on acute toxicity and has assigned the following risk phrases:

R23   Toxic by inhalation

R24   Toxic in contact with skin

R25   Toxic if swallowed

The technical grade manufacturing concentrate has a moderate acute inhalation toxicity.  It is also a dermal sensitising agent in guinea pigs.

The product, Metasystox R Systemic Insecticide, is a light brown liquid with a characteristic aromatic odour.  It demonstrated moderate oral (LD50 144 mg/kg in male rats and 135 mg/kg in female rats) and dermal (LD50 299 mg/kg in male rats and 116 mg/kg in female rats) acute toxicity.  The formulation was a slight dermal, and a moderate eye irritant in rabbits.  The product is likely to have dermal sensitisation potential.

Formulation, transport and storage

Oxydemeton-methyl products will be formulated in Australia.  All formulation procedures should be performed in closed vessels under air extraction and chemical testing should be done under fume hoods.  Formulators and packers should wear appropriate protective equipment such as chemical resistant clothing, gloves, safety boots and eye and respiratory protection.

Transport, storage and retail workers could only be exposed to oxydemeton-methyl or the products if packaging were breached.  Advice on safe handling of oxydemeton-methyl and products during routine formulation and end use is provided in the relevant material safety data sheets (MSDS).

End use

The product is proposed for the control of aphids in brassica vegetable crops, cotton and lupins and will be applied by individual operators or contract sprayers.  It will be used as a spray at various rates depending on the crop and aphid species being treated.  The application volume (spray) for brassica varies with the crop stage and may range between 300 and 1000 L/ha.  For cotton and lupins, the recommended spray volumes are 100 to 150 L/ha for ground spray and 30 to 50 L/ha for aerial spray.  The application rates for the three crops range between 0.15 L and 1.1 L (0.11-1.87% end-use-product and 0.028-0.467% oxydemeton-methyl).  Product application may be repeated if necessary.

Withholding Periods for harvesting brassica vegetable crops, cotton and lupins are 14 days, 21 days and 6 weeks, respectively.  Withholding Periods for grazing are 21 days and 6 weeks for cotton and lupins, respectively.  Grazing treated brassica vegetable crops is prohibited.

The following worker exposure study was submitted by the applicant to NOHSC and used to estimate the risk of health effects following repeated use of the products:

Inkmann-Koch, A.: Measurement of Applicator Exposure During Application of Metasystox-R on Beets. Bayer Report No. RA - 981/292B, November 1984.

In this study, dermal and inhalation exposures were measured following three different application scenarios of Metasystox R (250 g/L oxydemeton-methyl) on beets.

Evaluation of this study, plus supplementary information generated using UK POEM for Australian conditions, indicated that workers will be required to wear protective equipment when using the product.  The risk assessment indicates that:

1. chemical resistant clothing, elbow-length PVC gloves, impervious footwear and full face respirator with combined dust and gas cartridge are required when opening the container and preparing spray; and that

2. waterproof clothing, cotton overalls, elbow-length PVC gloves, impervious footwear and face shield or goggles are required when using the prepared spray.

Re-entry assessment

The draft label does not specify a re-entry period for any crop.  Oxydemeton-methyl has low vapour pressure.  Hence inhalation exposure is not expected to be significant. The main route of exposure upon re-entering sprayed areas would be dermal.

Oxydemeton-methyl has a half-life of 1 to 3.5 days in the soil.  No data is available on dislodgeable foliar residues.  The maximum concentration of oxydemeton-methyl in the spray, indicated under Australian conditions, is 0.47%.

NOHSC considers that a re-entry period of 24 hours would be appropriate in light of the information available.  Workers are therefore required to wear cotton overalls buttoned to the neck and wrist and chemical resistant gloves when entering treated areas within 24 hours of spray application or until the spray has dried.

The Withholding Periods on the draft label range between 2 and 6 weeks for harvesting and grazing, depending on crops.  Therefore the re-entry period will not interfere with harvesting and grazing.

Recommendations for safe use

Australian workers involved in formulation or packing of oxydemeton-methyl products should be protected by the use of engineering controls, such as, exhaust ventilation and enclosed vessels, by observing safe work practices and by receiving adequate training. They should wear appropriate protective equipment such as chemical resistant clothing, gloves, safety boots and full face respirators.  Testing of chemicals should be done under fume hoods.

End users should follow the instructions and Safety Directions on the product labels.  Safety Directions include the use of personal protective equipment (PPE), namely chemical resistant clothing, elbow-length PVC gloves, impervious footwear and full face respirator with combined dust and gas cartridge when opening the container and mixing/loading the product and protective waterproof clothing, cotton overalls, elbow-length PVC gloves, impervious footwear and face shield or goggles when using the prepared spray.  The PPE recommended should meet the relevant Standards Australia standard specified below:

  • AS 1337-1992 Eye Protection for Industrial Applications
  • AS/NZS 1715-1994 Selection, Use and Maintenance of Respiratory Protective Devices and AS/NZS 1716-1994 Respiratory Protective Devices
  • AS 2161-1978 Industrial Safety Gloves and Mittens (Excluding Electrical and Medical Gloves)
  • AS/NZS 2210-1994 Occupational Protective Footwear
  • AS 3765-1990 Clothing for protection against hazardous chemicals
  • Bayer Australia Limited has produced MSDS for oxydemeton-methyl and Metasystox R Systemic Insecticide.  These contain information relevant to Australian workers, as outlined in the NOHSC National Code of Practice for the Preparation of Material Safety Data Sheets.  Employers should obtain the MSDS from the supplier and ensure that their employees have ready access to it.

Conclusions

Metasystox R Systemic Insecticide can be used safely if handled in accordance with the instructions on the product label.  Additional information is available on the product MSDS.

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Environmental Assessment

Environmental Fate

Proposed use

The proposed use of Metasystox R Systemic Insecticide is for the control of aphids in brassica vegetable crops, cotton and lupins.  It is expected that application will be by ground rig (brassica vegetable crops, lupins and cotton) or by aircraft (cotton and lupins) as an EC spray.  Application rates are 1.1 L/ha (275 g ai/ha) or 100 mL/100 L for brassica vegetable crops; 150-300 mL/ha (37.5-75 g ai/ha) for cotton and for lupins either 300 mL/ha (75 g ai/ha) [cowpea and blue green aphid in WA] or 560 mL/ha (140 g ai/ha)[green peach and potato aphid in WA; all aphids in NSW, VIC and SA only].

There is a limited use pattern given on the label, with directions for a maximum of 3 applications on brassica vegetable crops, 2 on cotton and a single application on lupins.  Most applications on cotton are expected to occur in late summer to autumn and for lupins in late winter to early spring, before or during flowering.

Hydrolysis

The hydrolysis of oxydemeton-methyl was conducted at three pHs.  The mean half-lives at 25C and pH 4, 7, 9 were calculated to be 74, 32 and 1.37 days respectively.  In an earlier study using radiolabelled material, the half-lives at pH 4, 7, 9 and 25 C were determined as 94, 40 and 2.5 days respectively.  The major metabolite at pH 5 and 7 was monomethyl oxydemeton (S-2-(ethylsulphinyl)ethyl O-methyl hydrogen phosphorothiolate).  At pH 9 the only metabolise was 2-(ethylsulfinyl)ethylthiol, which was the minor metabolite at pH 7.  Oxydemeton-methyl is rated as slightly hydrolysable at 25 C and pH 7.

Photolysis

Aquatic

Based on a laboratory study performed, conducted according to US EPA guidelines, and theoretical studies based on the quantum yield of oxydemeton-methyl (ECETOC methodology), the photo degradation rate in water is rated as slightly degradable.  From the laboratory study, after 30 days in natural sunlight the degradation of parent was similar to that in the dark control, 86% versus 83%.  The calculation based on the quantum yield showed a half-life of > 100 days at latitude 30° North during summer.  In contrast a laboratory study using artificial light showed at half-life of 19 days of continuous irradiation for the non-sensitised system and with a sensitiser (acetone) the half-life was 4 days.  The major degradate identified in non-sensitised system was dimethyl phosphorothiolate, and for the sensitised system the major degradate identified was oxydemeton-methyl sulfone.

Soil

In a soil photolysis study, performed according to US EPA Guidelines, after 30 days in natural sunlight the degradation of oxydemeton-methyl in soil was similar for both exposed and dark samples, with half-lives calculated to be 61 and 53 days respectively.  This is a similar result to an older study, where the degradation was biphasic, with the first order regression analysis giving an overall half life of 95 days for artificial light which contrasts with the dark controls, where the half life was 36 days.  The photo degradation in soil should be a minor route of environmental degradation, even in Australia with high light levels during summer.

Metabolism

Aerobic soil metabolism

The first study was performed according to US EPA Guidelines.  A sandy loam soil was treated with oxydemeton-methyl and incubated under aerobic conditions for 1 year.  There were two significant metabolites formed, 2-(ethylsulfinyl)ethane sulfonic acid and 2-(ethylsulfonyl)ethane sulfonic acid.  The half-life over the first 21 days was calculated by first order analysis as 3.2 days.  A second study using a different sandy loam soil, again conducted according to US EPA Guidelines, showed there was <0.3% of parent left after the first 3 days.  The half-life for the first 3 days of degradation was calculated as 9.6 hours.  A third study, not performed to any Guidelines, using a silt loam, showed a half life of < 1 day.  Oxydemeton-methyl is classified as readily degradable in sandy loam and silt soils.

Aerobic Aquatic Metabolism

The study was not performed according to any Guidelines and used two different sediments, both loamy sands, together with the natural waters collected with the sediments.  Oxydemeton-methyl was added to the sediment/water systems under aerobic conditions and incubated in the dark for 91 days.  The overall half-lives were = 1 day for both sediment/water systems.  It was concluded that the degradation of oxydemeton-methyl was extremely rapid, and after 20 days, there were only traces of parent compound detectable in both systems. The degradation products were largely translocated into the sediment and then continuous mineralisation of the sediment bound material occurred.

Anaerobic Soil Metabolism

A study was performed according to US EPA Guidelines using a sandy loam soil treated with oxydemeton-methyl and incubated under aerobic conditions for 10 hours, then conditions changed to anaerobic by flooding with nitrogen.  There were two significant metabolites formed, both sulfonic acids, 2-(ethylsulfinyl)ethane sulfonic acid and/or 2-(ethylsulfonyl)ethane sulfonic acid, which were not separable in the HPLC analysis.  No half-life was able to be determined.  A second study using a silt loam soil, which was not performed to any standards, showed there was <2% of parent left after the first 14 days.  The half-life was calculated to be <1 day.  Again the major metabolites were the sulfonic acids as before.

Anaerobic Aquatic Metabolism

The study was performed according to US EPA Guidelines and used a loamy sand soil, together with the natural waters collected with the sediment.  Oxydemeton-methyl was added to the sediment/water systems under anaerobic conditions and incubated in the dark for a year.  The overall half-life was determined to be 3.5 days for the first 21 days of the study.  After 21 days there was 2% of parent compound left in the system.  Degradation then slowed.  The major degradation product was the reduced product, demeton-S-methyl, which was further degraded and the degradation products incorporated into the sediment.

Soil microorganisms

Several studies on the degradation of oxydemeton-methyl by isolated soil bacteria and fungi were presented.  The results show that oxydemeton-methyl does not affect these organisms and that both degrade oxydemeton-methyl by hydrolysis and redox reactions.

Mobility

Soil adsorption/desorption

The adsorption/desorption of oxydemeton-methyl was studied in three soils using a flask batch method but not to any Guideline.  The results of the experiment show that oxydemeton-methyl is weakly absorbed to the three soils tested (Kd 0.1-0.54) and was rated as having high mobility in soil.  In a second study performed to US EPA Guidelines, four soils were tested in a batch method and again oxydemeton-methyl was weakly adsorbed, Kd 0.01-0.45 (Koc 1.6-52.9).  It is concluded by Environment Australia that oxydemeton-methyl could be very mobile.

Leaching

In a soil column leaching study, not performed to Guidelines, using columns with five different microbially active soils, there was significant material in the leachate for both sandy loam and silt loam soils, approximately 17% of applied radioactivity.  Analysis of the soil in the column after 48 hours of leaching showed that there was movement of applied radioactivity, and for sandy loam and silt loam soils the majority of the applied radioactivity moved 20-25 cm down the columns.  The other soils showed less movement.  As there was no analysis of the columns, it was unclear whether this movement of applied radioactivity was due to oxydemeton-methyl or possible metabolites.  It was concluded that oxydemeton-methyl and its metabolites could be mobile, the extent of which is dependent on the organic content of the soil.

Leaching of aged soil residues

In an aged soil column leaching study performed, again not according to any guidelines, radio-labelled oxydemeton-methyl was aerobically incubated in a sandy loam for 30 days, then the soil added to a column of similar soil before being leached for 45 days.  The results show that there was limited movement though the soil column of the metabolites (applied radioactivity), with 87% remaining in the aged soil and 6.4% of applied radioactivity in the leachate.  A second study using a sandy clay loam soil and a similar method as before showed again there was little vertical movement of the applied radioactivity.  Detailed analysis showed that <0.2% of the radioactivity in the aged soil was parent compound and that most of the radioactivity had been lost during the ageing or was in the organic fraction of the soil.  The only metabolites identified in the leachate were sulfonic acid metabolites, 2-(ethylsulfinyl)ethane sulfonic acid and 2-(ethylsulfonyl)ethane sulfonic acid.

Lysimeter study

In a ten year lysimeter study using a range of agricultural chemicals that included oxydemeton-methyl, no parent compound was detected in the leachates.  The lysimeters were treated as for normal agricultural practice in Germany, with crop rotations and chemicals applied timed to local farm practice, and exposed to natural rain fall.  Environment Australia concludes that field leaching of oxydemeton-methyl is very unlikely, mainly due to the rapid degradation.

Soil volatilisation

Oxydemeton-methyl was applied to the surface of a sandy loam soil then air was passed over the soil in a volatility apparatus and the volatile fraction in the air stream trapped.  3.3% of the applied radioactivity was recovered as carbon dioxide but no volatile organics were observed.  Analysis of the soil revealed that the parent material had degraded in the soil, consistent with the aerobic soil metabolism study, to non-volatile sulfonic acids.  Environment Australia concludes that oxydemeton-methyl is not volatile from the surface of soil.

Volatilisation in a field experiment

Oxydemeton-methyl was applied to wheat in pots then the plants and soil sampled over the next 24 hours.  While there was some apparent volatilisation from the plants, Environment Australia concluded that this was within the experimental variation and that there was no real evidence of volatilisation.

Spray drift

Recent literature studies on aerial spray drift show that the 95th percentile from a number of experiments gave spray drift results of 0.35% of the application rate at approximately 300 metres.  Thus, one in twenty aerial applications result in 0.35% of the application rate as spray drift at 300 metres from the edge of the field being sprayed.  Under adverse conditions, i.e. inversion layers, the 95th percentile for spray drift increases to 1 % of the application rate.

Field dissipation

No field studies were submitted by the company.  Given the rapid degradation in the soil metabolism studies, very limited persistence of oxydemeton-methyl is expected.  As a result soil accumulation from one year to the next is not expected.

Bioaccumulation

Fish were exposed to two concentrations of radio-labelled oxydemeton-methyl under flow-through conditions for 28 days.  There was no evidence of any bioaccumulation, with the level of radioactivity in the fish being at or below the level in the water.  Bioaccumulation in the aquatic environment is not expected.

Summary of ecotoxicity

Avian

The acute LD50 for bobwhite quail was found to be 17 mg/kg (confidence limit 15-19 mg/kg) for males and 18.5 mg/kg (confidence limit 14.5-23.5 mg/kg) for females in a study performed according to early US EPA Guidelines.  In an older study on a range of birds species, not performed to current standards, pigeons were found to be the most sensitive, LD50 of 14.9 mg/kg, with the chakar partridge the least sensitive, LD50 of 113 mg/kg.

Acute dietary studies showed that the LD50 for the bobwhite was 361 ppm (CL 272-483 ppm) and for the mallard the LD50 was 2003 ppm (CL 1444-4160 ppm).  The NOECs were 33 ppm for the bobwhite and 141 ppm for the mallard.  These studies were performed to current US EPA Guidelines.

One generation reproduction studies were performed to current US EPA Guidelines using both bobwhites and mallards.  The NOEC for the bobwhite was 10 ppm and for the mallards the NOEC was 30 ppm, as determined by Environment Australia.

Aquatic

The acute toxicity of oxydemeton-methyl to rainbow trout and golden orfe was determined according to OECD Guidelines.  The acute LC50 for trout, using a formulation different to that proposed for Australia, was 109 mg/L of formulation, confidence limit 50-200 mg/L, corresponding to 12 mg ai/L (CL 5.5-22).  The NOEL was 2.8 mg ai/L.  For golden orfe using the technical grade active, the LC50 was 436 mg ai/L with confidence limits of 290-670 mg ai/L. The NOEC was determined by Environment Australia as <3.8 mg/L.

In addition, a number of older studies were presented, not performed to current standards.  The toxicity of oxydemeton-methyl TGAC (92.3% purity) to rainbow trout was 17 mg ai/L (CL 12-22 mg ai/L).  For Metasystox R (oxydemeton-methyl 250 EC) the LC50 to rainbow trout was 15.5 mg/L (CL 12.7- 18.9 mg/L), to golden orfe the LC50 was 28.2 mg/L (CL 27.4-29.1 mg/L) and to bluegill the LC50 was 26 mg/L (20-32 mg/L), all expressed as milligrams of formulation.

The chronic toxicity of Metasystox R (oxydemeton-methyl 250 EC) to rainbow trout under flow-through conditions was determined according to OECD Guidelines.  The LD50 (21 days) was determined by Environment Australia to be between 3.3-15.3 mg/L of formulation (0.79-3.8 mg ai/L) and the NOEC 3.3 mg/L of formulation (0.79 mg ai/L).  An early life stage test (fertilised eggs to fingerlings, 98 days) was conducted according to US EPA Guidelines using Metasystox manufacturing concentrate (50% ai).  The NOEC was 2.6 mg ai/L and the LOEC 4.9 mg ai/L.

The acute toxicity of Metasystox manufacturing concentrate (50% ai) to Daphnia magna was determined according to OECD Guidelines.  The 48 hour EC50 was 0.16 mg ai/L (confidence limits 0.13-0.18 mg ai/L) and the NOEC was <0.1 mg ai/L.  The study was considered acceptable.  Other older studies were presented which were not performed according to international Guidelines.  The LC50 for these studies were 0.75 mg/L for the test substance (53.8% ai) and between 10 and 90mg/L (corrected for a dilution error in the report), again for the test substance (50% ai).  Under flow-through conditions in a test conducted according to US EPA Guidelines using technical oxydemeton-methyl (94.8% ai), the acute LC50 was 0.19 mg ai/L, confidence limits 0.17-0.22 mg ai/L.

The chronic toxicity of Metasystox R (250 EC) to Daphnia magna was determined over a 21 day period under semi-static renewal conditions according to OECD Guidelines.  The NOEC (immobilisation) was 0.22 mg/L of formulation, equivalent to 0.057 mg ai/L. There was no effect on reproduction at the doses used.  Another 21 days chronic test using D. magna was conducted but under flow-through conditions according to US EPA Guideline and using technical oxydemeton-methyl (94.8% ai).  The EC50 was graphically determined to be 0.046 mg ai/L and the NOEC was 0.027 mg ai/L.

There were two additional aquatic species tested, marine shrimp and crabs.  The study was not performed according to current guidelines and used Metasystox R (EC 250 g ai/L).  All results were nominal.  The LC50 for shrimp was between 0.87 and 1.8 mL/L of formulation, equivalent to 0.22 and 0.45 mg ai/L, based on the stated purity of the formulation.  For the crabs, the EC50 is given as 8.6 mL/L (CL 6.6- 11 mL/L), equivalent to EC50 = 2.15 mg ai/L (CL 1.65-2.75 mg ai/L).

Two algae studies were presented, both performed according to OECD Guidelines.  For the first, using the manufacturing concentrate (51.3% ai), the NOEC was > 100 mg/L of the test substance.  In the second test using Metasystox R (EC 250), the EbC50 was calculated as 22 mg/L of formulation after 96 hours and the EC50 as 49 mg/L, based on measured concentrations and the NOEC was 3.8 mg/L (nominal).  As the formulation control, without the active ingredient, showed a high level of inhibition, it was considered that the results are mainly due to the formulation additives.

Non-target invertebrates

Bees

No studies on the toxicity of oxydemeton-methyl to bees were presented. The applicant states that there are no bee studies in English and acknowledges that oxydemeton-methyl is highly toxic to bees.  A US EPA database (Ecological Effects Branch, Pesticide EcoToxicity Database) has the following endpoints: 48 hour contact LD50s 3 mg per bee (Tech, material); 2.15 mg per bee (25.4% ai; bees 3-4 days old) and 24.4 mg per bee (25.4% se, bees 5-6 days old).

Earthworms

An acute study was performed according to OECD Guideline 207 using technical oxydemeton-methyl (96% ai).  The LD50 was given as 115 mg/kg of soil and the NOEC 0.1 mg/kg of the TGAC.  The NOEC was from the range finding study.  The acute toxicity of the EC formulation (250 g ai/L) was determined according to the OECD guidelines and found to be 670 mg/kg of formulation, (CL 442-1299 mg/kg), corresponding to 167 mg ai/kg (CL 110-325 mg ai/kg).  It was noted that the formulation blank in this earthworm study gave high mortalities, similar to the highest tested concentration, but as the technical material gave similar results, the formulation was not considered to be the primary toxicant.

The chronic toxicity of the spray formulation Metasystox R SL 100 ( 111 g ai/L, not proposed for Australia) was determined according to a draft ISO Guideline.  The study lasted for 56 days and was a single generation worm study.  The NOEL was given as 3.75 kg/ha, expressed as formulation applied to the surface of the test soil and the LOEL 12.5 kg/ha.

Effects on beneficial arthropods

In a semi-field study conducted according to a Guideline from the German Federal Biological Research Centre, parasitic wasps were introduced into apple trees before being sprayed with Metasystox R (EC 250 g ai/L). The toxic effects on the wasps were of short duration, with the level of parasitation returning to control levels after a few days. Accordingly, it was concluded that over the whole experiment there was no significant reduction in parasitation, except for the first day.

Effect on soil microflora respiration and nitrogen

The effect of oxydemeton-methyl on soil respiration was determined according to a non-standard (in-house) method while the effect on nitrogen turnover was determined according to German Guidelines.  From the results of these studies, Environment Australia concludes that there is unlikely to be any significant effect on soil respiration or nitrification.

Effect on Carabid beetles

The effect on Metasystox R (EC 250 g ai/L) under laboratory conditions and semi-field conditions (wheat field, potato crops and in wheat stubble) was determined.  These are non-standard tests and the test organisms are not present in Australia, although there are a large range of predatory beetles in Australia.  These tests showed that while there were significant mortality of the beetles in laboratory conditions at 500 g ai/ha (37% mortalities), in the semi-field tests the number of mortalities was not statistically significant different from controls.  During the semi-field test in the wheat field it was noted that there was a reduction in the number of web spiders for the first 4 days but no effect on rove beetles or other invertebrates from application of Metasystox R.

Phytotoxicity

No information of the phytotoxicity of oxydemeton-methyl was forwarded by the applicant.  There is a statement that "No impact on terrestrial plants is expected as the exposure is low in the proposed crops and field trials have not revealed any evidence of terrestrial phytotoxicity".  Environmental Australia does not expect oxydemeton-methyl to show significant phytotoxicity.

Predicted environmental hazard

Terrestrial organisms

Mammals

Aerial applications could overspray animals, such as marsupials, but this is not considered a common occurrence due to the low height of the spray aircraft at application and it is expected that these animals will move some distance away from the spraying operations, while smaller mammals will be undercover.  Similarly, overspray by tractor powered equipment is considered unlikely.  A hazard to animals entering recently sprayed areas is also considered unlikely, based on the expected residues in treated areas and the moderate mammalian toxicity.

Birds

As for mammals above, birds are not expected to be directly oversprayed but they could receive a dermal dose.  As birds do not generally use or feed in either cotton or lupins, the exposure, and therefore the hazard, is expected to be low.  However, birds are known to feed in vegetable crops, presumably including brassica vegetable crops.  Calculations on the concentration of residues on leafy crops from applications at 275 kg ai/ha show that residues are significantly less than the most sensitive acute dietary end point for birds and therefore the hazard to birds consuming sprayed crop is expected to be low.

Bees and other terrestrial invertebrates

Bees are at risk if spraying occurs when they are present in the crop.  As a rule, brassica vegetable crops are harvested before flowering and therefore the hazard to bees is expected to be low.  For other brassica vegetable crops that flower before harvest, and for lupins, provided Metasystox R is not sprayed when bees are foraging, the exposure, and therefore the hazard, is expected to be low.  As cotton is not a significant source of pollen or nectar for bees, the risk to bees from application to cotton is considered low.  The semi-field studies showed that there were no effects on rove beetles and only limited effects on web spiders and carabid beetles, therefore only limited effects are expected on other non-target invertebrates.

Soil invertebrates

Earthworms and other soil dwelling invertebrates could be exposed to the pesticide, and at an application rate of 275 kg ai/ha, calculations show that the top 5 cm of soil would contain residues significantly below the EC50for earthworms and therefore effects on earthworms are not expected.  However, it should be noted the tested earthworm, Eisenia foetida, is normally considered insensitive to chemicals.

Aquatic organisms

Aerial applications

First tier - direct overspray

For aerial application to cotton, a direct overspray to a body of water 15 cm deep at the maximum application rate of 75 g ai/ha is calculated to give a concentration in the water of 0.050 mg/L.  This is significantly below the most sensitive result for fish, LC50 = 3.9 mg/L and the hazard to fish is low.  For daphnia the most reliable endpoint, EC50 = 0.16 mg/L, indicates that effects on daphnia are possible.  For lupins the maximum rate is 140 g ai/ha and the concentration in water from direct overspray is 0.093 mg/L.  There is a low hazard to fish and possible hazard to daphnia, as for cotton.

The hazards to fish from overspray in both cotton and lupins are considered acceptable and no further refinement to the hazard for fish is required.  For daphnia there are possible effects and further refinements to more accurately determine the hazard are required.

Second tier-10% spray drift onto pond

Using the US EPA assumption that 10% spray drift occurs, this provides a concentration of 5 mg/L and 9.3 mg/L for lupins for a shallow pond 15 cm deep for cotton application.  Using the same endpoint as above for daphnia, the hazard was calculated as low.

For aquatic invertebrates there was only one study that gave a result that would indicate a possible hazard to invertebrates, that of the older study which is not considered reliable.  Nevertheless, a brief examination of the current situation with respect to aerial application in cotton is considered useful to fully explore the potential hazard.  With the current introduction of the Best Management Practices Manual for cotton, which recommends a 300 metre downwind buffer and the results of spray drift studies, the spray drift is expected to be <0.35% of the application rate for 95% (19 in 20) of all applications.  From the new AgDRIFT model from the US EPA and modeling for finer droplets, more typical of application expected in Australia, the spray drift at 300 metres was 3.2% of the application rate.  Using the older (corrected) LD50 of 16.5 mg ai/L, effects on daphnia are not expected provided best practice, i.e. the BMPM for cotton or Operation Spray Safe: Pilots and Operators Manual, is used and followed.

Applications by boomspray

Second tier-10% spray drift onto pond

Applications by boomspray are normal for brassica vegetable crops and lupins and can be used for dry land cotton.  While boomsprayers are not noted for spray drift in general and direct overspray is consider to be unlikely, assuming a 10% spray drift at the maximum rate of 275 g ai/ha for brassica vegetable crops gives a concentration in water (15 cm deep) of 18.3 mg ai/L.  Using the reliable EC50 for daphnia above, the hazard to daphnia was calculated as low but the less reliable result indicates that a hazard is possible.

Recent literature reports have shown that as close as 1.7 metres to the spray boom there is less than 2% spray drift for 95% of insecticide applications using cone nozzles, even in winds of 20 km/h.  Another figure used is 1% at 5 metres away from the site of application, based on studies done on herbicides using fan nozzles whereas insecticides are sprayed using cone type nozzles.  The USA Spray Drift Task Force results for boomsprayers show that using cone nozzles, there is 0.5% spray drift deposited at 30 metres from the sprayer even with a breeze of 18 km/h.  (The boom spray section in the new AgDRIFT model is based on the results of the Spray Drift Task Force and predicts 0.56% of the application rate at 30 metres from low boom spraying.)  Based on these results there is unlikely to be significant effects on daphnia at reasonable distance from water courses, say 10 metres or so, using the most sensitive endpoint for daphnia and the hazard is low.

Multiple applications

Applications per season are limited to 3 to brassica vegetable crops, 2 to cotton, and 1 to lupins.  Assuming that respraying occurs to cotton within 7 days - due to high insect pressure, the highest rate is used each time and a shallow billabong 300 metres away is affected by spray drift, then there is no increase in concentration expected in the water due to the previous application 7 days earlier, calculated by Environment Australia using a half life of 1 day in water.  Similarly, for brassica vegetable crops there is no increase in concentration in the water expected as a result of a previous application 7 days earlier.  It is concluded that there should be no increase in the hazard due to multiple applications, provided there is at least 7 days between applications.

Runoff and leaching

Runoff from areas where oxydemeton-methyl has been applied could be contaminated by the chemical.  Calculations show that assuming that 10% of a catchment is treated with oxydemeton-methyl and 10% of the application runs off, the concentration in the runoff wafer is significantly less than the EC50 for the most sensitive organisms tested, daphnia, and the hazard from runoff is considered low.

Algae

The EbC50 for algae was determined as 5.5 mg ai/L, which is approximately 3 orders of magnitude higher than the EEC from 10% spray drift and effects on algae are therefore not expected.

Conclusion

Environment Australia considers that the hazard from the proposed uses is low for mammals and birds and high to bees and possibly other non-target terrestrial insects.  The hazard to earthworms was considered low.

When applied by air the hazard to fish was considered to be low as is the hazard to daphnia and other aquatic invertebrates, the most sensitive organisms, when used according to best agricultural guidelines, i.e. the new Best Management Practice Manual for Cotton Growers or Operation Spray Safe: Pilots and Operators Manual.

The spray drift hazard from boom sprayers is low to aquatic invertebrates near to the spray operations. Runoff from treated areas is not considered a hazard to aquatic invertebrates, based on the aquatic organisms tested.

In conclusion, Environment Australia can support the use of Metasystox R systemic Insecticide (250 g/L, oxydemeton-methyl) as proposed.

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Efficacy and Safety Assessment

Proposed use pattern

Oxydemeton-methyl is proposed to be used by ground rig or by air to control aphid pests of brassica vegetable crops, cotton (NSW, QLD, NT and WA only) and lupins (NSW, VIC, SA and WA only).  Detail of the use patterns can be seen in the directions for use table on the draft product label (pp. 31 - 34).

Metasystox R Systemic Insecticide will be available in 1 L, 5 L, 10 L, 20 L and 200 L containers.

The rate of use varies between crops; 1.1 L/ha for brassica vegetable crops; 300 mL/ha for cotton; and 300 mL/ha or 560 mL/ha for lupins, depending on aphid pest being controlled.  The maximum number of applications proposed per season are 3 for brassica vegetable crops, 2 for cotton and 1 for lupins.

Harvest and grazing withholding periods have been recommended as follows:

Crop Withholding period
Grazing Harvest
Brassica vegetable crops Do not graze 14 days
Cotton seed 21 days 21 days
Lupins 6 weeks 6 weeks

Evaluation of efficacy data

Data presented by Bayer Australia Limited supported claims that Metasystox R Systemic Insecticide adequately controls aphids in brassica vegetable crops, cotton and lupins.  The data were gathered from a range of replicated and unreplicated trials.

The data were adequate (with appropriate discussion) to satisfactorily assess efficacy when used according to the label directions (See pp. 31 - 34).

Phytotoxicity

All trials reported no observed phytoxicity from the application of Metasystox R Systemic Insecticide to brassica vegetable crops, cotton or lupins.

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Labeling. Requirements

The draft label for the product is given below.  It reflects the assessments made by the APVMA.

DANGEROUS POISON

KEEP OUT OF REACH OF CHILDREN

READ SAFETY DIRECTIONS BEFORE OPENING OR USING

Metasystox(r) R Systemic Insecticide

Active Constituent:  250 g/L OXYDEMETON-METHYL (an anticholinesterase compound)

Solvent:  348 g/L XYLENE

GROUP 1B INSECTICIDE

For control of aphids on brassica crops, cotton and lupins as specified in the directions for use table

1, 5, 10, 20, 200 Litres

Directions for Use

Crop Pest Rate Critical Comments
Brassica vegetable crops Aphids 100 mL/100 L

 

or

1.1 L/ha

Spray when pests are first seen and repeat when necessary.  Add a wetting agent.

 

A maximum of 3 applications of Metasystox R should be applied to any one crop.

Cotton (QLD NSW WA ONLY) Aphids 150 - 300 mL/ha Spray when pests are first seen and repeat when necessary.  Use the higher rate for heavy infestations.

 

A maximum of 2 applications of Metasystox R should be applied per season.

Lupins Aphids (NSW VIC SA ONLY) 560 mL/ha

Check crops at regular intervals throughout the season.  Infestation may occur at any time, but are most common during the late vegetative and budding-flowering period.  Spraying is warranted if more than 30% of the counted tips are infested with 5 or more aphids; and at least 15% of the crop is infested to this level.  Apply by aircraft or ground misters

A border spray to control early infestations that generally invade from the crop perimeter is recommended.

WA ONLY

The lower rate will not control green peach aphid.  If unsure of aphid identification or if mixed aphid populations occur, use the higher rate.

A maximum of 1 application of Metasystox R should be applied per season.

Green peach aphid

Potato aphid

(WA ONLY)

560 mL/ha

Cowpea aphid

Blue green aphid

(WA ONLY)

300 mL/ha

NOT TO BE USED FOR ANY PURPOSE, OR IN ANY MANNER, CONTRARY TO THIS LABEL UNLESS AUTHORISED UNDER APPROPRIATE LEGISLATION

THIS PRODUCT IS TOO HAZARDOUS TO BE RECOMMENDED FOR USE IN THE HOME GARDEN

WITHHOLDING PERIODS:

HARVEST

BRASSICAS: DO NOT HARVEST FOR 14 DAYS AFTER APPLICATION

COTTON: DO NOT HARVEST FOR 21 DAYS AFTER APPLICATION

LUPINS:   DO NOT HARVEST FOR 6 WEEKS AFTER APPLICATION

GRAZING

BRASSICAS: DO NOT GRAZE ANY TREATED AREA OR CUT FOR STOCK FOOD

COTTON: DO NOT GRAZE OR CUT FOR STOCK FOOD FOR 21 DAYS AFTER

  APPLICATION

LUPINS:   DO NOT GRAZE OR CUT FOR STOCK FOOD FOR 6 WEEKS AFTER

  APPLICATION

General Instructions

Mixing

Add the required quantity of Metasystox R to water in the spray vat while stirring or with agitators in motion.

Closed mixing/loading is recommended when available.

Precaution

DO NOT use manual flaggers in aerial spraying unless protected by engineering controls.

 

Re-entry period

DO NOT allow entry into treated areas for 24 hours after treatment.  When prior entry is necessary, wear cotton overalls buttoned to the neck and wrist and chemical resistant gloves.  Clothing must be laundered after each day's use.

Insecticide Resistance Warning

GROUP 1B INSECTICIDE

For insecticide resistance management, Metasystox R is a Group 1B insecticide.  Some naturally occurring insect biotypes resistant to Metasystox R and other Group 1B insecticides may exist through normal genetic variability in any insect population.  The resistant individuals can eventually dominate the insect population if Metasystox R and other Group 1B insecticides are used repeatedly.  The effectiveness of Metasystox R on resistant individuals could be significantly reduced.  Since occurrence of resistant individuals is difficult to detect prior to use, Bayer Australia Limited accepts no liability for any losses that may result from the failure of Metasystox R to control resistant insects.  Metasystox R may be subject to specific resistance management strategies.  For further information contact your local supplier, Bayer representative or local agricultural department agronomist.

Compatibility

Metasystox R is compatible with most commonly used insecticides and fungicides including Antracol(r), Dipterex(r) 500 SL, Helothion(r) and Tokuthion.  The compatibilities given are based on world-wide experience and are considered correct.  However, as changes in climatic conditions can alter the sensitivity of plants to mixtures of sprays, we accept no responsibility for the behaviour of such mixtures.

Protection of Livestock

Dangerous to bees.  DO NOT spray any plants in flower while bees are foraging.

Protection of Wildlife, Fish, Crustaceans and Environment

DO NOT contaminate ponds, waterways and drains with the chemical or used container.

A strategy to minimise spray drift should be employed at all times when aerially applying sprays near sensitive areas.  Such a strategy is illustrated by the cotton industry's "Best Management Practice Manual".

Storage and Disposal

Store in the closed, original container in a well ventilated area, as cool as possible.  Do not store for prolonged periods in direct sunlight.  Triple or (preferably) pressure rinse containers before disposal.  Add rinsings to spray tank.  Do not dispose of undiluted chemicals on-site.  Break, crush, puncture and bury empty containers in a local authority landfill.  If not available bury the containers below 500 mm in a disposal pit specifically marked and set up for this purpose clear of waterways, vegetation and roots.  Empty containers and product should not be burnt.

Safety Directions

Poisonous if absorbed by skin contact, inhaled or swallowed.  Repeated minor exposure may have a cumulative poisoning effect.  Obtain an emergency supply of atropine tablets 0.6 mg.  Will irritate the eyes and skin.  Avoid contact with eyes and skin.  Do not inhale vapour or spray mist.  Repeated exposure may cause allergic disorders.  When opening the container and preparing the spray, wear chemical resistant clothing buttoned to the neck and wrist and a washable hat, elbow-length PVC gloves, impervious footwear and full face respirator with combined dust and gas cartridge.  When using the prepared spray, wear protective waterproof clothing, cotton overalls buttoned to the neck and wrist and a washable hat, elbow-length PVC gloves, impervious footwear and face shield or goggles.  If product on skin immediately wash area with soap and water.  If product in eyes, wash it out immediately with water.  If clothing becomes contaminated with product or wet with spray, remove clothing immediately.  After use and before eating, drinking or smoking, wash hands, arms and face thoroughly with soap and water.  After each day's use wash gloves, face shield or goggles, contaminated clothing and respirator and if rubber wash with detergent and warm water.

First Aid

If poisoning occurs, contact a doctor or Poisons Information Centre (Phone 131126).  If swallowed, give one atropine tablet every 5 minutes until dryness of mouth occurs.  If poisoned by skin absorption or through lungs, remove any contaminated clothing, wash skin thoroughly and give atropine tablets as above.  Get to a doctor or hospital quickly.

For further information refer to the Material Safety Data Sheet for the product.

Liability

This product must be used strictly as directed.  Bayer Australia Limited may not be liable for loss or damage arising from failure to follow directions for use.

(r)Trademark of Bayer Germany MN

(c)Copyright Bayer Australia Limited   APVMA Approval Number

Organophosphorus Pesticides, Liquid, Toxic, Flammable (oxydemeton-methyl)

(TOXIC 6.1 DIAMOND)

(FLAMMABLE LIQUID DIAMOND)

UN No. 3017

PG III

Bayer Australia Limited emergency contact
1 800 033 111
Australia wide, 24 hours

 

Bayer Australia Ltd
875 Pacific Highway
Pymble NSW 2073
Telephone (02) 9391 6000

Bayer

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Glossary

Active constituent The substance that is primarily responsible for the effect produced by a chemical product.
Acute Having rapid onset and of short duration.
Carcinogenicity The ability to cause cancer.
Chronic Of long duration.
Codex MRL Internationally published standard maximum residue limit.
Desorption Removal of an absorbed material from a surface.
Efficacy Production of the desired effect.
Formulation A combination of both active and inactive constituents to form the end use product.
Genotoxicity The ability to damage genetic material
Hydrophobic Water repelling
Leaching Removal of a compound by use of a solvent.
Log Pow Log to base 10 of octonol water partitioning co-efficient.
Metabolism The conversion of food into energy
Photo degradation Breakdown of chemicals due to the action of light.
Photolysis Breakdown of chemicals due to the action of light.
Subcutaneous Under the skin
Toxicokinetics The study of the movement of toxins through the body.
Toxicology The study of the nature and effects of poisons.

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References

Felton, J.C., Oomen, P.A. & Stevenson, J.H. 1986, 'Toxicity and hazard of pesticides to honeybees: harmonisation of test methods', Bee World, vol. 67, no. 3, pp. 114-24.

Goring, C.A.I. et al. 1975, 'Principles of pesticide degradation in soil', in Environmental Dynamics of Pesticides, edited by R. Haque and V.H. Freed, Plenum Press, New York, pp 135-72.

Matthews, G.A. 1992, Pesticide Application Methods, 2nd ed., Longman, London.

Australian Pesticides and Veterinary Medicines Authority 1996, Ag Manual: The Requirements Manual for Agricultural Chemicals, APVMA, Canberra.

Australian Pesticides and Veterinary Medicines Authority 1997, Ag Requirements Series:  Guidelines for Registering Agricultural Chemicals, APVMA, Canberra.

Australian Pesticides and Veterinary Medicines Authority 1996,  MRL Standard: Maximum Residue Limits in Food and Animal Feedstuffs, APVMA, Canberra.

Australian Pesticides and Veterinary Medicines Authority 1997, Ag Labeling. Code-Code of Practice for Labeling. Agricultural Chemical Products, APVMA, Canberra.

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