an investigation of clopyralid and aminopyralid in commercial composting systems

Report Version 7 - Final

An investigation of clopyralid and

aminopyralid in commercial

composting systems

A review of existing research on the occurrence, fate and management of residual risks from the herbicides clopyralid and aminopyralid during PAS 100 green waste composting processes and subsequent application of composts to susceptible agricultural crops.

Project code: OAV031-002 Research date: June 2009 to May 2010

Date: October 2010

WRAP helps individuals, businesses and

local authorities to reduce waste and

recycle more, making better use of

resources and helping to tackle climate

change.

Document reference: WRAP, 2009, An investigation of clopyralid and aminopyralid in composting systems. Project OAV031-

002. Report prepared by Dr E Jane Gilbert, Josef Barth, Enzo Favoino and Dr Robert Rynk. .

Written by: Dr E Jane Gilbert, Josef Barth, Enzo Favoino and Dr Robert Rynk

Front cover photography: Harvesting grass for silage

WRAP, Dr E Jane Gilbert, Josef Barth, Enzo Favoino and Dr Robert Rynk believe the content of this report to be correct as at the date of writing. However, factors such as

prices, levels of recycled content and regulatory requirements are subject to change and users of the report should check with their suppliers to confirm the current

situation. In addition, care should be taken in using any of the cost information provided as it is based upon numerous project-specific assumptions (such as scale,

location, tender context, etc.).

The report does not claim to be exhaustive, nor does it claim to cover all relevant products and specifications available on the market. While steps have been taken to

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An investigation of clopyralid and aminopyralid in commercial composting

systems 3

Executive summary

Clopyralid and aminopyralid are herbicides that retard the growth of some plants by mimicking natural plant

hormones (auxins). They have been licensed internationally to control annual and perennial broadleaf weeds in

certain crops, turf and pastureland. When the manufacturers‘ guidelines are followed, herbicide residues should

not be present in materials destined for composting, and the resulting composts will present no risks to crops.

However, there have been a number of reported incidences in the USA and New Zealand where herbicide

residues have been identified in composting feedstocks and composted products. When present in these

products, the residues have been associated with phytotoxic effects in susceptible plants, including commercially-

grown crops such as tomatoes.

The objectives of this project were to: Review existing research on the occurrence, fate and management of

residual risks from the herbicides clopyralid and aminopyralid during BSI PAS 100: 2005 green waste composting

processes and subsequent application of composts to susceptible agricultural crops; To review previous examples

where residual risks from these herbicides had been realised and managed elsewhere in the world; To collate this

information and identify options for managing any identified residual risks from these herbicides to sensitive

crops.

Based on the information gathered during this study, risks from persistent herbicide contamination of composts

are thought to be low.

Clopyralid is sold for both amateur and professional use in the UK, either singly, or in conjunction with other

herbicides. A total of 34,344 kg (34.3 tonnes) of clopyralid was applied to agricultural land in 2006 over an area

of 304,738 ha across Great Britain. During 2009 a total of 867 kg was sold in amateur products, equivalent to

2.5% of the 2006 agricultural application estimate. Data on quantities of aminopyralid sold for professional use

during these periods were not available – no formulations of this compound are currently available for amateur

use. Neither compound presents a risk to human health, animal health, crops or the wider environment if used

according to their manufacturers‘ instructions.

The difficulty for compost site operators is that clopyralid and aminopyralid are effective at very low

concentrations, and that treated plant material may accidentally enter composting feedstocks from a variety of

diffuse (non-point) sources, which means that standard HACCP procedures may not be sufficient to prevent

unsuitable material from being processed. The feedstocks of concern are grass and animal manures. However,

for herbicide residues in the finished composts to be present at a sufficient dose to impact upon sensitive crops

when those composts are used, a significant quantity of herbicide-contaminated material must be composted

together for a sufficiently short time and the composts be applied to sufficiently sensitive crops at sufficiently high

rates. Such coincidences of circumstance are known to have occurred in the USA and New Zealand, and although

uncommon they do prompt questions about the suitability of composts for particularly sensitive end uses.

Clopyralid degradation during composting is highly variable: degradation appears to be biphasic (i.e. degradation

occurs in two separate phases); the composting temperature appears to affect the rate of degradation (it is faster

at higher temperatures); the initial concentration of clopyralid affects its rate of degradation (it is slower at higher

initial concentrations); and, the rate of degradation is faster during the active phase of composting compared

with the maturation phase. Once applied to soil, the rate of degradation of clopyralid appears to be dependent

upon moisture, temperature, the application rate, the extent of aerobicity in the soil and the amount of organic

matter. Notably clopyralid binds to organic matter, which appears to slow degradation. Clopyralid is stable in

anaerobic environments and has a high leachability potential.

In a number of studies increases in clopyralid concentrations during the early phases of composting were noted,

due to the faster rate of degradation of organic matter. Half-lives of between 10 to 30 days were reported,

although in one experiment degradation was not observed even after 112 days. These studies indicate that short

composting periods may not be sufficient to degrade clopyralid should it be present in composting feedstocks.

However, as most compost applied to fields would be ploughed prior to planting crops, it seems likely that

potential contamination would present a minimal risk. Where compost has been used as a mulch (for example, in

the growth of top fruit) no incidences of herbicide effects have been documented.

Aminopyralid displays many similar properties to clopyralid: it is stable in water, is stable to anaerobic

degradation and is highly mobile in the soil. Aminopyralid is rapidly degraded via photolysis, whereas clopyralid is


systems 4

stable to light. The main routes of dissipation of aminopyralid appear to be through mineralisation and soil

leaching. Aminopyralid appears to be more stable than clopyralid in soil (half-life of 103.5 days compared with 25

days, respectively). It has been suggested that aminopyralid has a greater biological activity than clopyralid.

The review did not identify any research assessing the degradation of aminopyralid during composting.

Based on the information gathered during this study, risks from persistent herbicide contamination of composts

are thought to be low, particularly from aminopyralid, use of which is now more strictly controlled. However, we

have set out a number of recommendations aimed at either preventing or reducing the possible risks of clopyralid

contamination in compost.

The extent to which there is potential for contaminated grass (or other green wastes) to enter a commercial

composting facility through a municipal waste collection service and to cause problems is currently unquantified,

however, the most robust long term strategy to ensure compost quality is to eliminate the potential for

contamination to occur at source. As long as these products are sold for amateur use, the onus should remain on

herbicide manufacturers to provide clear, practical, easy-to-follow advice to householders for recycling grass and

other garden wastes following herbicide application – and for householders to follow this advice.

The challenges faced by local authorities in meeting their targets to divert biodegradable municipal waste from

landfill should not be underestimated; hence disposal of grass or other green wastes in residual (mixed or ‗black

bag‘) waste collections should not be encouraged.

Based on experience from other countries where herbicide residues are known to have impacted upon sensitive

crops through composts, appropriate bioassay testing is expected to give the most direct assurance of compost

quality. A suitable bioassay is already compulsory within the PAS 100 specification, but it is recommended that

the existing PAS 100 bioassay be validated:

Using compost containing concentrations of clopyralid known to adversely affect plant growth;

Against red clover (Trifolium pratense), as this has a high degree of sensitivity to clopyralid and ability to

produce observable results after 14 days; and

Against the test methods described by Brinton et al., 2005, and the Recycled Organics Unit, 2007c, as

these were developed specifically to identify low concentrations of herbicide in the growing medium.

The extent to which compost manufacturers can control clopyralid contamination in feedstocks is limited.

However, we recommend that compost site operators:

Remain vigilant to the potential for clopyralid contamination during late spring and summer when the

input of grass clippings is likely to be at its greatest, and ensure that this is adequately addressed in

HACCP plans (where appropriate);

Communicate with suppliers of feedstocks to highlight the potential for contamination through the use of

clopyralid-containing herbicides. This may take the form of a Contract of Supply with landscapers,

grounds maintenance and sports turf professionals to highlight the potential for contamination, and

ensure, as far as reasonably practicable, that feedstocks are not delivered for composting within a year

of clopyralid application. Information on the risks and safe management of treated feedstocks could be

developed for communication to professionals when they deliver feedstocks to a composting site. These

initiatives could usefully be achieved through a joint exercise between with the manufacturers of

clopyralid, the composting industry and in consultation with WRAP;

Consider increasing the frequency of bioassay testing for composts intended for use in growing media or

to raise protected crops, however, it is acknowledged that this will entail additional costs;

Ensure that high-risk composted animal manures be sent for use in non-sensitive applications. This

could be addressed through a contract of supply (which already exists for agricultural and field

horticultural crops through the Compost Quality Protocol in England and Wales). As a matter of course,

compost producers should make their customers aware of the suitability of their composts for different

end uses;

Adhere to the 2010 WRAP Guidelines for the Specification of Quality Compost for use in Growing Media

for all compost sold for use in either growing media or protected crops.


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Contents

1.0 Introduction ................................................................................................................................ 8 2.0 Methodology ............................................................................................................................... 8 3.0 Properties of clopyralid and aminopyralid ................................................................................. 9

3.1 Chemical and physical properties .......................................................................................... 9 3.2 Toxicology .......................................................................................................................... 9 3.3 Biological mode of action and target plants .......................................................................... 10 3.4 Licensed applications in the UK ........................................................................................... 11

3.4.1 Clopyralid ............................................................................................................. 11 3.4.2 Aminopyralid ........................................................................................................ 12

4.0 Herbicide dissipation and degradation pathways.................................................................... 13 5.0 Clopyralid dissipation and degradation ................................................................................... 14

5.1 Dissipation and degradation in soils .................................................................................... 14 5.2 Dissipation and degradation of clopyralid during composting ................................................. 15

5.2.1 Composting feedstocks .......................................................................................... 15 5.2.2 Fate during composting ......................................................................................... 15

5.3 Aminopyralid dissipation and degradation ............................................................................ 18 5.4 Composting feedstocks ...................................................................................................... 19

6.0 Compost contamination: an historical perspective ................................................................. 20 6.1 Clopyralid ......................................................................................................................... 20

6.1.1 Concentrations detected ........................................................................................ 20 6.1.2 The situation in Washington State, USA .................................................................. 21

6.2 Aminopyralid..................................................................................................................... 22 6.3 Picloram ........................................................................................................................... 22

7.0 Compost testing and bioassays ................................................................................................ 23 8.0 Effects of clopyralid and aminopyralid on plant growth ......................................................... 23

8.1 Application issues .............................................................................................................. 23 8.2 Effect of clopyralid on crop rotation .................................................................................... 23 8.3 Translocation in Canada thistle and biological activity ........................................................... 24 8.4 Translocation into tree leaves ............................................................................................. 24 8.5 Enclosed growing of crops in polytunnels and glasshouses .................................................... 24 8.6 Rainfall ............................................................................................................................. 24 8.7 Compost application rates .................................................................................................. 24

9.0 Managing the risks ................................................................................................................... 25 9.1 Composting feedstocks ...................................................................................................... 25 9.2 Compost use ..................................................................................................................... 27

9.2.1 Agriculture and field horticulture ............................................................................ 27 9.2.2 Growing media and protected crops ....................................................................... 27 9.2.3 Landscaping and grounds maintenance ................................................................... 27

10.0 Recommendations .................................................................................................................... 28 10.1 Municipal wastes ............................................................................................................... 28 10.2 Compost manufacturers ..................................................................................................... 28 10.3 Compost testing ................................................................................................................ 29

11.0 References ................................................................................................................................ 30 Appendix 1 ............................................................................................................................................ 33 Appendix 2 ............................................................................................................................................ 40 Literature review of garden waste composition .................................................................................. 40 12.0 Introduction .............................................................................................................................. 40

12.1 Results from England .................................................................................................... 40 12.1.1 Morpeth, Northumberland ...................................................................................... 40 12.1.2 Dogsthorpe, Peterborough ..................................................................................... 41 12.1.3 Nine English local authorities.................................................................................. 41

12.2 European data ............................................................................................................... 43 12.2.1 Hamburg, Germany ............................................................................................... 43 12.2.2 Aarhus, Denmark .................................................................................................. 43

12.3 Conclusions .................................................................................................................... 43


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Figures

Figure 1 – Clopyralid-induced damage in a tomato plant ................................................................................ 10 Figure 2 – Fates of pesticides in compost applied to soil ................................................................................ 13 Figure 3 – Seasonal variation in proportion of grass clippings collected in green / food waste co-collection at

Castle Morpeth in 1995/96 .......................................................................................................................... 41 Figure 4 – Variation in grass collected in a garden / food waste collection scheme in Hamburg, Germany .......... 43

Tables

Table 1 - Physico-chemical properties of clopyralid and aminopyralid ................................................................ 9 Table 2 - Summary toxicological properties of clopyralid and aminopyralid ........................................................ 9 Table 3 – Application of clopyralid to various crop types in 2006 (Great Britain) ............................................... 12 Table 4 – Environmental fates of clopyralid (soil and water) .......................................................................... 14 Table 5 - Measured half-lives of clopyralid in composting feedstocks .............................................................. 17 Table 6 – Degradation and fate of aminopyralid ............................................................................................ 18 Table 7 – Concentrations of aminopyralid in harvested crops in Canada and North America .............................. 19 Table 8 – Summary of compost contamination by clopyralid .......................................................................... 20 Table 9 – Composting feedstocks and their potential to be contaminated with clopyralid .................................. 26 Table 10 – Clopyralid-containing products sold in the UK for amateur use ....................................................... 33 Table 11 – Clopyralid-containing products sold in the UK for professional use .................................................. 34 Table 12 - Aminopyralid-containing products approved for use in November 2009 ........................................... 37 Table 13 - Aminopyralid-containing products approved for use before July 2008 .............................................. 37 Table 14 - Picloram containing products registered in the UK ......................................................................... 39 Table 15– Summary of green waste composition in the Morpeth trial .............................................................. 40 Table 16– Summary of green waste composition at Dogsthorpe ..................................................................... 42


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Glossary

a.e. Acid equivalent

Auxin Plant hormones that control plant growth and behaviour

Biphasic degradation Degradation occurring in two separate phases, usually with different decay rates

CAS Chemical Abstracts Service registry number

DAT Day(s) after treatment

DT 50 DT50 is the time required for the pesticide concentration under defined conditions to decline

to 50% of the amount at application.

Ha Hectare

IUPAC International Union of Pure and Applied Chemistry reference

LOQ Limit of Quantitation

OM Organic matter

PHI Pre-harvest interval

Ppb Parts per billion i.e.

Ppm Parts per million i.e.

SOM Soil Organic Matter

t1/2 Half life, which is the time taken for the concentration to decrease by 50%

US EPA United States Environmental Protection Agency

Acknowledgements

The authors are grateful to the following individuals for providing information and insight:

Ron Alexander - Ron Alexander Associates, USA

Dr Will Brinton - Woods End Laboratory, USA

Dan Caldwell - CER-Compost, USA

Angus Campbell, Recycled Organics Unit, New South Wales, Australia

Jeff Gage - Compost Design Services, USA

Elaine Gotts – Scotts Ltd, UK

Steve Higginbotham - Stewardship Ltd, UK

Ruth Rogers – Chemicals Regulation Directorate, UK

David Senior – Vitax Ltd, UK

Anne Thompson and Andy Bailey - Dow AgroSciences, UK

Jennifer Thwaites – Horticultural Trades Association, UK

Chris Wild - Rigby Taylor Ltd, UK


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1.0 Introduction Clopyralid and aminopyralid are herbicides that retard the growth of some plants by mimicking natural plant


certain crops, turf and pastureland. Although extremely effective in their intended uses, herbicide residues have

been identified in composting feedstocks and composted products in the USA and New Zealand, where they have

been associated with phytotoxic effects in susceptible plants, including commercially-grown crops such as

tomatoes.

Based on scientific literature, a risk assessment of the application of composted green wastes to agricultural land

by the Macaulay Land Use Research Institute (2009), suggested that clopyralid may present a risk to crop plants

following compost application. The objective of this work, therefore, was to review existing research on the

occurrence, fate and management of residual risks from the herbicides clopyralid and aminopyralid during BSI

PAS 100 green waste composting processes and subsequent application of composts to susceptible agricultural

crops. Specifically, this report:

Summarises the occurrence and fate during composting of the herbicides aminopyralid and clopyralid

within commercial composting systems;

Summarises the environmental fates of aminopyralid and clopyralid residues in soil; and

Provides options for managing any identified residual risk(s) to sensitive crops from aminopyralid and

clopyralid.

2.0 Methodology This study comprised a comprehensive literature review followed up by direct contact with relevant individuals

and organisations.

In conducting the literature review, search terms were established, including synonyms and spelling variations. A

number of on-line databases (e.g. PubMed and Agricola) and search engines e.g. Google Scholar and

www.ojose.com were interrogated using the standardised search terms. Hand searches of conference

proceedings (e.g. ORBIT proceedings) and grey literature held by the consortium partners were conducted.

Literature in German, Italian, Spanish and Swedish were also searched:

In Germany, the archive of the German Compost Quality Assurance Organisation (the BGK), databases

of the Environmental Information System of the State of Baden-Wuerttemberg UIS-BW (where most of

the research on organic pollutants in compost and soils is carried out) were reviewed;

In Sweden, Samsoek (which provides access to 41 Swedish Libraries at the Swedish Agricultural

University SLU) and the Biological Waste Treatment Working Group at the Swedish Waste Management

Association were contacted.

Information from the Chemicals Regulation Directorate (formerly the Pesticides Safety Directorate) and product

safety data sheets from licensed manufacturers of clopyralid and aminopyralid were obtained.

Each acquired document was assigned a unique reference number, then graded depending upon whether it was

peer reviewed, a technical or non-technical report, then catalogued in a database alongside a short summary.

This was used as the basis of a secondary literature screen, in which publications cited in reports obtained in the

initial screen were obtained. Search terms were expanded accordingly.

http://www.ojose.com/


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3.0 Properties of clopyralid and aminopyralid Clopyralid and aminopyralid are herbicides that retard the growth of some plants by mimicking natural plant


certain crops, turf and pastureland. Specific information about these herbicides is detailed below.

3.1 Chemical and physical properties Clopyralid and aminopyralid are both pyridine carboxylic acid compounds and their key properties are summarised

in Table 1 (Dow AgroSciences, 1998, and PPDB web site, 2009 a and b).

Table 1 - Physico-chemical properties of clopyralid and aminopyralid

Property Clopyralid Aminopyralid

Chemical name 3,6-dichloro-2-pyridinecarboxylic acid (CAS*)

3,6-dichloropyridine-2-carboxylic acid

(IUPAC**)

3,6-dichloropicolinic acid

4-amino-3,6-dichloro-2-pyridinecarboxylic

acid (CAS*)

4-amino-3,6-dichloropyridine-2-carboxylic

acid (IUPAC**)

Molecular mass 192.0 207.0

Empirical formula C6H3Cl2NO2 C6H4Cl2N2O2

Structural formula

Chemical family Pyridine carboxylic acid Pyridine carboxylic acid

Solubility in water High High

Volatility Low Low

Leachability Groundwater Ubiquity Score (indicator of

leachability) = 5.06 (high)

Groundwater Ubiquity Score (indicator of

leachability) = 4.78 (high)

Koc - Organic-

carbon sorption

constant (ml g-1)

***

5 (very mobile)

Decreases with increasing pH

8 (very mobile)

Decreases with increasing pH

* Chemical Abstracts Service registry number

** International Union of Pure and Applied Chemistry reference *** The Koc measures the affinity for pesticides to sorb to organic carbon: the higher the value, the stronger the tendency to attach to and move with carbon in soils. Koc values greater than 1000 indicate strong adsorption to soil, whilst chemicals with lower Koc values (less than 500) tend to move more with water than be adsorbed to sediment.

3.2 Toxicology Both clopyralid and aminopyralid appear to present a low risk to human health and exhibit low to moderate

ecotoxicity across a range of indicator species (Table 2; PPDB web site, 2009 a and b).

Table 2 - Summary toxicological properties of clopyralid and aminopyralid

Toxicity Clopyralid Aminopyralid

Eco toxicity Low to moderate, although may affect some

arthropods

Low bioaccumulation potential

Low to moderate

Low bioaccumulation potential

Human health Not acutely toxic

Unknown reproduction / development effects

Respiratory tract irritant

Not acutely toxic

Eye irritant

http://en.wikipedia.org/wiki/File:Clopyralid.png

http://en.wikipedia.org/wiki/File:Aminopyralid.svg


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3.3 Biological mode of action and target plants Clopyralid and aminopyralid are chemicals that mimic indole acetic acid (IAA), a plant growth hormone (auxin),

that induces cell elongation and division (Tu et al., 2001). They bind to the IAA receptor sites in plant cells,

thereby preventing the natural auxin from exerting its normal effect. As such, they impede the growth of certain

plants, resulting in stunted growth (see below), and ultimately death (Dow AgroSciences, 1998). They are used

as post-emergence herbicides (that is, they are applied after the weeds have started to grow; PPDB web site,

2009 a and b). Both clopyralid and aminopyralid are systemic, and enter plants through both the roots and

leaves; clopyralid is known to be translocated through the plant through both the xylem and phloem tissues,

effectively impacting all parts of the growing plant (Dow AgroSciences, 1998). Symptoms of clopyralid activity

have been documented as (Dow AgroSciences, 1998):

inhibited root and shoot growth;

thickened roots and inhibited root hair production;

thickened, curved, and twisted shoots, stems and leaves;

parallel venation (narrow leaves with callus tissue);

cupping and crinkling of leaves;

callus (hardened) growth on stems;

cracked stems; and

proliferated growth.

An example of clopyralid damage is shown in Figure 1.

Figure 1 – Clopyralid-induced damage in a tomato plant


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Clopyralid targets four major broadleaf families (Dow AgroSciences, 1998) namely:

Asteraceae, which is sometimes referred to as the Compositae (commonly known as the aster, daisy, or

sunflower family); includes plants such as sunflower, cocklebur, ragweed, chicory, scentless chamomile,

Canada thistle, knapweed, dandelion, and perennial sow-thistle;

Fabaceae, which is sometimes referred to as Leguminosae (commonly known as the legume, pea, bean

or pulse family); includes plants such as clover, black medic, vetch and mesquite;

Solanaceae, commonly known as the nightshade family or potato family; includes plants such as

nightshade, bryony, tomato and aubergine; and

Polygonaceae, commonly known as the knotweed family; includes plants such as fat hen and docks.

Aminopyralid is also effective against species in the Asteraceae (Compositae), Fabaceae (Leguminosae) and

Solanaceae families.

Both aminopyralid and clopyralid are used to control broadleaf weeds in grasslands (agricultural and amenity).

3.4 Licensed applications in the UK 3.4.1 Clopyralid Clopyralid is sold for both amateur (nine products) and professional (35 products) use in the UK (see Table 10

and Table 11 in Appendix 1), either singly, or in conjunction with other herbicides. Formulation and

concentrations vary between products and are dependent upon crop types, which influence application rates and

restrictions, such as timing of application before harvest or flowering.

Clopyralid is marketed by a number of companies, but sales data are limited. Agricultural application rates were

available from the Food and Environment Research Agency (Pesticides Usage Statistics web site, 2009) for 2006

(the latest year for which data were available), and are summarised in Table 3. A total of 34,344 kg (34.3

tonnes) of clopyralid was applied in 2006 to a treated area of 304,738 ha across Great Britain. By contrast, a total

of 867 kg was sold in amateur products in 2009 (David Senior and Elaine Gotts, Personal Communications),

equivalent to 2.5 % of the 2006 agricultural application estimate.

Labels on amateur products recommend use between April – September (Verdone), and April – October (Vitax),

which both coincide with the maximum quantities of grass clippings received at composting sites (see Appendix

2). Due to the complexities of retail supply chains, data were not available to assess variability of sales

throughout the year; however, data supplied by the Horticultural Trades Association indicated that perceived

sales of lawn care fertilizers1 peaked during April and May (Jennifer Thwaites, Personal Communication; data not

shown). Collectively 89 % of perceived sales were made between April and October, again coinciding with the

period during which grass clippings could be received at composting sites.

Sales data were only available from a minority of suppliers providing clopyralid formulations for professional (lawn

care) applications. These data indicate that 367 kg were sold into this market during 2009 (David Senior and

Chris Wild, Personal Communications), but the true figure is thought to be significantly higher than this.

1 As specific sales data for clopyralid containing products were unavailable, we obtained data on sales of lawn care fertilizers on the assumption that purchasing trends and use of these products would likely mirror those of lawn care herbicides. Data were supplied by the Horticultural Trades Association as part of their Garden Industry Monitor and are based on consumer perceived spend rather than actual sales.


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Table 3 – Application of clopyralid to various crop types in 2006 (Great Britain)

Crop

Total area treated*

(ha)

Total mass applied

(kg)

Cereals 1,779 366

Oil seeds 67,430 5,422

Peas and beans 440 40

Potatoes 7.7 <1

Set aside 11,203 1,335

Beet crops** 93,536 7,098

Other arable crops 4,544 411

Vegetable brassicas 1,337 155

Lettuce and other leafy salad ND ND

Onions and leeks 1,845 113

Carrots and parsnips ND ND

Other root vegetables 50 4.7

Other outdoor vegetables 852 65

Maize and sweetcorn 1,716 188

Other fodder crops 274 34

Grassland 123,026 19,357

Top fruit and hops 12 1.7

Strawberries 790 93

Other soft fruit 79 10

Outdoor ornamental crops 808 102

Protected edible crops ND ND

Protected ornamental crops*** <1 <1

Mushrooms ND ND

* Area treated refers to the active substance treated area. This is the basic area treated by each active

substance, multiplied by the number of times the area was treated e.g. A field of 3 ha is treated 4 times with

active X. Therefore, the area treated is 12 ha (3x4)

** This includes sugar beet and beetroot, as well as fodder beet and mangels

*** This includes edible plants for propagation

ND No data were available, either for 2006 or the preceding years, suggesting that clopyralid was not recorded

as used on these crops.

The data in Table 3 suggest that animal feed crops and grassland are the largest recipient of

clopyralid in the agricultural sector.

3.4.2 Aminopyralid Aminopyralid is licensed for sale in the UK in nine products (as of November 2009) to control a range of weeds on

grassland for grazing by sheep and cattle. Use of the treated grass is restricted, with silage making or hay

harvesting from treated land not permitted within one year following application of the herbicide. Aminopyralid is

also available for professional use in amenity situations to control pernicious or invasive weeds (Chemicals

Regulation Directorate, 2009) (Table 12). Until July 2008 eight products were approved for a variety of

applications (Table 13), however, approvals for their sale, supply and use were suspended temporarily in 2008 by

the (former) Pesticides Safety Directorate (now the Chemicals Regulation Directorate; Pesticides Safety

Directorate, 2008a). Products were marketed by two companies, Dow AgroSciences Ltd and AgChemAccess Ltd

(a brokerage service for agrochemical products). Dow AgroSciences have stated that they are the sole

manufacturer globally (Dow, 2008).

The previously licensed products are listed in Table 13 in the Appendix (Association for Organics Recycling web

site, 2009). Notably only one was licensed for amateur use, although this was never marketed (Anne Thompson,

Dow AgroSciences, Personal Communication), with the remainder licensed for use by professionals, principally to

control deep-rooted perennial weeds in grassland, including docks, thistles, nettles, and ragwort (Manure Matters

web site, 2009).


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Of the six million hectares of managed grassland2 in the UK, approximately 114,000 ha of agricultural grassland

were treated with a product containing aminopyralid during 2008 (Anne Thompson, Dow AgroSciences, Personal

Communication).

4.0 Herbicide dissipation and degradation pathways There are a number of different ways in which pesticides (including herbicides) may be either degraded or

dissipated in the environment. This has been summarised graphically in Figure 2 (derived from the Recycled

Organics Unit, 2007b).

Figure 2 – Fates of pesticides in compost applied to soil

Reproduced with permission of the Recycled Organics Unit in New South Wales, Australia.

Büyüksönmez et al. (1999 and 2000) reviewed the occurrence, fate and degradation of pesticides during

composting. Biological, chemical and physical mechanisms all play a role, and are dependent upon the pesticide‘s

properties and the environment in which it has been applied. The authors summarised the fates as:

Adsorption;

Leaching;

Volatilisation;

Abiotic transformation processes (hydrolysis, photolysis, advanced oxidation processes); and

Biological transformation (either complete or partial mineralisation).

Büyüksönmez et al. (1999) also noted that the degradation of pesticides during composting appears to be similar

to that in soil, therefore they concluded: ―the behaviour of a particular pesticide in soil should be a reasonable

approximation of what might occur during composting‖. However, they also noted that the high temperatures

occurring during composting, the high levels of organic matter and biological activity may affect degradation. In

particular, adsorption, humification, biologically-mediated transformation and volatilisation may play more

important roles. Fogarty and Tuovinen (1991) discussed the effects of composting parameters on pesticide

degradation, although the study did not specifically discuss clopyralid or aminopyralid.

2 This includes grass for grazing by any form of livestock or horses and grass intended for forage production i.e. silage, hay or haylage.


systems 14

5.0 Clopyralid dissipation and degradation Summary data of the fates of clopyralid in water and soil are summarised in Table 4 (Dow AgroSciences, 1998

and PPDB web site, 2009b).

Table 4 – Environmental fates of clopyralid (soil and water)

Environment Degradation mechanism and time scale

Aquatic Photolysis (DT50 = 271) – classed as stable

Dow states that there is no significant degradation from sunlight

t1/2 = 261 days at 25 °C

Stable to direct hydrolysis – classed as very persistent

Stable in aerobic and anaerobic water – no significant degradation

Soil Typical soil, average half-life = 25 days

Range = 8-250 days (19 soils)

Less than 69 days in 95% of the soils

Shorter half-life in warm, moist soils and lower application rates

DT50 in soil = 34 days (moderately persistent)

Anaerobic Soil Metabolism - no significant degradation

Major degradation occurs through microbial action, with CO2 being the only

significant metabolite.

Degradation is enhanced with lower application rates, higher soil moisture and

temperature.

Potential for particle bound transport index = low

Koc - Organic-carbon sorption constant (ml g-1) = 5 (very mobile). Binding to organic matter increases over time.

DT50 = is the time required for the pesticide concentration under defined conditions to decline to 50% of the

amount at application.

Hydrolysis = a chemical reaction in which a molecule is cleaved into two parts by the addition of a molecule of

water.

5.1 Dissipation and degradation in soils

Technical information published by Dow AgroSciences (1998) suggested that clopyralid degradation occurs via

aerobically-mediated microbial processes. Studies assessing its effect on soil microbial activity (five different soil

types) suggested that clopyralid (at 1 and 10 ppm) did not affect nitrification, nitrogen fixation or respiration.

Early studies investigating the fate of clopyralid in Canadian soils by Pik et al., 1977 indicated that:

Degradation was microbially mediated;

The rate of degradation was influenced by moisture content and was fastest in moist soils

(t1/2 = approximately 2 months);

The rate of degradation was inversely related to the soil organic matter content;

The rate of degradation was dependent upon season (being fastest during summer and slowest in

winter), suggesting temperature plays a role; and

Leaching was also inversely related to the soil organic matter (SOM) content – as adsorption was directly

related to the SOM.

The importance of soil micro-organisms was shown by Ahmad et al., (2003) who conducted laboratory-scale

experiments in sterilised and non-sterilised soils. Clopyralid concentrations decreased with a t1/2 of 7.3 days (at

20 °C) in the non-sterilised soil compared to a t1/2 of 57.8 days in the sterilised soil. Dissipation was also shown

to be temperature dependent (t1/2 of 4.1 days versus 46.2 days at 30 and 10 °C, respectively).


systems 15

Smith and Aubin (1989) measured the dissipation of clopyralid in three prairie soils (clay, clay loam and sandy

loam) at different temperatures. They found that dissipation increased as the temperature increased (from 10 to

30 °C), and showed first-order kinetics. Half lives ranged from 10 to 47 days, and were similar in the clay and

sandy loam soils, and greatest in the clay loam soil at higher temperatures. The authors did not disclose the

organic matter content of the test soils.

Clopyralid has a high leachability potential, which suggests it may leach into groundwater. However, Dow

AgroSciences (1998) and others (Tu et al., 2001) suggest that, in practice, this may not be as great as calculated

from its physico-chemical properties. Cox et al. (1996) measured the leaching and adsorption of clopyralid in

laboratory-based soil columns (one sandy and two silty clay soils). The experiments suggested that clopyralid

was poorly adsorbed to the soils. Notably these soils had low levels of organic matter (0.57 % sandy soil, and

1.29 % and 1.48 % in the silty clay soils), and in the experiments the greatest variation from predicted

adsorption to the soils occurred in the soil with the highest level of organic matter.

A number of researchers have suggested that light may also play a role, as dissipation in field-scale experiments

was slowest in shaded pasture and shaded bare ground compared to un-shaded plots (Ahmad et al., 2003). This

has been supported recently by bench-scale research by Abramović et al., (2007) who examined the

photocatalytic removal of clopyralid in water. They noted at a range of pH values (1 to 9) that clopyralid was

stable for at least two months, in the presence or absence of sunlight. However, they found that in the presence

of ultra violet light degradation was over 30-times faster than the rate of photocatalytic degradation under visible

light.

Notably, clopyralid does not appear to be degraded in anaerobic environments (either soil or water), which may

have implications for anaerobically treated materials (e.g. manures and slurries treated in an on-farm anaerobic

digester). Further research in this area is recommended, in particular, to assess whether post-aerobic treatment

of digestates (both the liquor and fibre) would subsequently reduce concentrations of the herbicide.

In summary, the rate of degradation of clopyralid in soil appears to be dependent upon the following variables:

Moisture – degradation is retarded in dry soils Temperature – degradation slows in cold soils

Clopyralid application rate – higher application rates appear to slow degradation Extent of aerobicity in the soil – degradation is slow in anaerobic soils

Amount of organic matter – binding to organic matter increases with time, which

appears to slow degradation

5.2 Dissipation and degradation of clopyralid during composting

5.2.1 Composting feedstocks There does not appear to be much evidence to suggest that clopyralid degrades in grassland or crops once it has

been applied. Dow notes that studies conducted on pasture grass, corn, spring wheat and cabbage indicated

that clopyralid was not metabolised or degraded by these crops (Dow AgroSciences, 1998). Clopyralid occurs in

plants as the unmetabolized parent acid, which might therefore be directly inputted to a composting process.

Metabolic studies in animals have suggested that in ruminants and poultry, clopyralid is excreted rapidly and

unchanged in the urine. In chickens, it was detected unchanged in the droppings. Whilst this is beneficial from a

toxicological point of view, it means that manures may be a potential source of contamination if subsequently

used as composting feedstocks.

5.2.2 Fate during composting A number of studies have been published, both in the peer-reviewed and grey literature, on the change in

concentrations of clopyralid during composting. These have been summarised below.

Vandervoort et al. (1997) conducted field studies of clopyralid dissipation on turf grass applied at a rate of 650 g

/ ha in conjunction with triclopyr (220 g ha-1). Grass was cut, then composted, with one pile turned regularly,

and one pile left unturned. Samples were taken from both the inside and outsides of the piles. Temperature and

moisture content were not monitored. Notably, the grass was not mixed with any other materials before

composting and the pile sizes were very small (approx. 0.5 m3): grass clippings do not compost well on their


systems 16

own, and could be expected to compost at lower temperatures and under less aerobic conditions than are

common in a commercial composting environment.

Clopyralid concentrations decreased from 32,000 ppb to 900 ppb in the outer samples of the turned piles and

from 1,560 ppb to 1,300 ppb in the inner samples of the turned piles after 365 days of composting (98% and

17% reductions, respectively). Concentrations in the unturned piles decreased from 7,200 ppb to 600 ppb and

6,800 ppb to 100 ppb, in the outer and inner samples after 365 days of composting (92% and 99% reductions,

respectively). This demonstrated a variable reduction in measured concentrations over a year. However, as

some crops may be sensitive to concentrations as low as 3 ppb (see Section 8.0), residual concentrations noted in

this study were still greatly (33 times) in excess of threshold concentrations for some crops, suggesting that

significant phytotoxic potential remained. The authors also noted that the pesticides studied, including clopyralid,

tended to show biphasic degradation: an initial fast rate of degradation (thought to be due to abiotic factors e.g.

volatilisation or photolysis), followed by a much slower rate (due to microbial degradation).

Brinton and Blewett (2004) tested levels of clopyralid in commercially-produced composts and investigated the

degradation of clopyralid in bench-scale laboratory reactors simulating garden leaf-waste composting. They

found that the rate of degradation of clopyralid was:

Dependent on temperature (greater at 35 °C than at 24 °C);

Dependent on the initial concentration of clopyralid – an inverse relationship was observed (the half-life

increased as the initial concentration increased); and

Approximately twice as fast during the active stage of composting (sanitisation) compared with

maturation (curing).

The researchers also noted an apparent increase in clopyralid concentrations during the early stages of

composting, which they attributed to a decrease in organic matter at a greater rate than clopyralid degradation.

They suggested that under typical composting conditions clopyralid exhibited a half-life of approximately 30 days.

The fact that clopyralid degradation was slower at higher concentrations is curious: it suggests an inhibitive

effect, however, clopyralid is known to exhibit low toxicity to micro-organisms (Dow AgroSciences, 1998). This

observation merits further investigation.

A study carried out in New South Wales, Australia, also showed that clopyralid (and a related herbicide, picloram)

did not decrease during composting (after 16 weeks) of shredded garden waste that had a moisture content of

between 55-65%. An increase in concentration of clopyralid was also observed during the study period (between

9 and 12 weeks) (Recycled Organics Unit, 2007a). This was observed both with low (approx. 17 ppb) and high

(50 ppb) initial clopyralid concentrations, however, the final concentration of clopyralid at both application rates

was still found to be greater at the end of the 16 week test period (approx 27 ppb and 53 ppb for the low and

high application rates, respectively).

These studies indicate that short composting periods may not be sufficient to degrade clopyralid should it be

present in composting feedstocks.

Brinton and Blewett (2004) also tested clopyralid-containing compost from the Spokane (Washington State, USA)

composting facility. They re-wetted then incubated samples at 35 °C and 24 °C, and observed that the decline in

concentration was greatest at 35 °C, with degradation occurring slowly at 24 °C (ambient). In all the tests,

clopyralid concentrations appeared to be dependent upon composting conditions. Maintaining composting

temperatures above ambient therefore appears to enhance the rate of degradation.

In an attempt to assess whether clopyralid formulation (granular vs. sprayable) and different mowing regimes

(mulching mower and clippings collected with a rotary mower) affected clopyralid concentrations, Washington

State University conducted a series of trials on turfgrass during 2002 (Miltner et al., 2003). There were some

differences in concentrations in the clippings between the two formulations (the concentration being greater

initially in the plot treated with the sprayable formulation). They found that, in general, the mowing regime did

not affect clopyralid concentrations in the collected grass clippings, which decreased logarithmically (t1/2 was

approximately 10 days). The authors concluded that, based on this rate of decrease, it would take over a year

for clopyralid concentrations to decrease to levels where the grass could be used as compost feedstock without

restriction.


systems 17

Researchers in Lithuania (Lubytė et al., 2007) assessed the effect of clopyralid dissipation in three substrates:

chopped straw, high moor peat and pine wood sawdust, and found that the half-life was 23 days in the straw and

peat, and 21 days in sawdust. They also investigated the effects of adding a mixture of humic acids (humate)

and a commercially available live microbial preparation used to treat septic tanks. They found that the additives

did not affect the rate of decrease of clopyralid concentrations. However, it was unclear from the results

presented how much loss was due to microbial degradation and how much was due to leaching losses. The

researchers did note that 64 – 73% of clopyralid was lost during the first 30 days. No residues of clopyralid were

detected 450 days after application.

The biphasic degradation noted by researchers (Vandervoort et al., 1997, and Lubytė et al., 2007) deserves

further research. It may be that the initial "disappearance" is partially due to adsorption to organic matter (OM)

and the latter phase is due to microbial decomposition/leaching of the adsorbed molecules as the OM

decomposes. (Concentrations of the pesticides are measured relative to dry matter content and not ash). This

attributed binding to organic matter is not expected based on clopyralid‘s low organic-carbon sorption constant

(Koc; Table 1). It has also been suggested that degradation appears to slow later in the composting process,

which may be attributed to increased humification of the organic matter (hence tighter binding to the herbicide).

These observations illustrate the complexity of the issue and highlight the need to ensure the active composting

process is carried out over a reasonable length of time, although this will also be dictated by feedstock types,

potential levels of contamination and composting method.

The measured half-lives of clopyralid in composting experiments vary between 10 and 30 days (summarised in

Table 5), depending upon composting conditions and feedstocks, although in one experiment, concentrations

were not found to decrease after 16 weeks (112 days) (Recycled Organics Unit, 2007a). Degradation rates

therefore appear to be highly variable and merit further investigation, for example, to assess whether there is a

relationship between the extent of humification or lignification in the substrates, and whether the carbon to

nitrogen ratio (and, more importantly, the available nitrogen) has any effect.

Table 5 - Measured half-lives of clopyralid in composting feedstocks

Feedstock Measured half-life

(Days)

Reference

Leaf-garden waste 30 Brinton and Blewett, 2004

Grass 10 Miltner et al., 2003

Straw 23 Lubytė et al., 2007

Peat 23 Lubytė et al., 2007

Sawdust 21 Lubytė et al., 2007

Although the half-life provides a useful measure of the time taken for the concentration to decrease by 50%, as

biphasic degradation has been noted in a number of experiments, the rate of degradation in the second (slower)

phase may well be the most important from both a composter‘s and end user‘s perspective.

Only one reference to the composting method was identified. When problems arose at the Spokane composting

facility in eastern Washington State, USA, composting site managers changed the composting method from that

of an open-air turned windrow to using an AgBag (enclosed composting system). This did not, however, affect

clopyralid concentrations (Bezdicek et al., 2001).

Clopyralid degradation appears to be variable. Key points to note include:

Biphasic degradation (i.e. degradation occurring in two separate phases) was noted by a

number of authors;

The composting temperature appears to affect degradation rates (faster degradation occurs

at higher temperatures);

The initial concentration of clopyralid affects its rate of degradation (it is slower at higher

concentrations);

The rate of degradation is faster during active composting compared with maturation;

An increase in clopyralid concentrations during the early phases of composting have been

noted, due to the faster rate of degradation of organic matter;

Half-lives of between 10 to 30 days were noted, although in one experiment no degradation

was observed after 112 days (Recycled Organics Unit, 2007);


systems 18

Clopyralid concentrations in grass clippings following application to turf were not affected

by mowing methods; and

No degradation in plants or animals following ingestion have been observed

5.3 Aminopyralid dissipation and degradation The literature review did not identify any studies that specifically assessed the concentration or fate of

aminopyralid during composting; instead, data based on environmental studies have been described below.

In reviewing the regulatory submission by Dow AgroSciences, the United States Office of Prevention, Pesticides

Environmental Protection and Toxic Substances Agency in 2005 (US OPPEPTC Agency, 2005) summarised the

fates of aminopyralid in a number of different environments. Data taken from this and two other sources (PMRA,

2007 and the PPDB web site, 2009a) are summarised in Table 6.

Table 6 – Degradation and fate of aminopyralid

Environment Degradation mechanism and time scale

Aquatic Photolysis is primary degradation mechanism (t1/2 = 0.6 days)

Photolysis – classed as fast

Stable to direct hydrolysis – classed as very persistent

Stable in anaerobic water sediments – DT50 = 712 days

Slow degradation in aerobic water (t1/2 = 462 to 990 days)

Soil Rate of degradation varied depending upon soil (types not stated) (t1/2 = 31.5 to

533.2 days in 5 soils)

The US EPA* used a half-life of 103.5 days

Health Canada states that biotransformation in aerobic soils is fast 6–39 days, but

was very slow in a clay loam soil (t1/2 = 330 days)

Photolysis on the soil surface was slow (t1/2 = 72 days)

Adsorption onto soil was weak

Two field dissipation studies suggested aminopyralid had a half-life (t1/2) of 20 and

32 days

Minimal leaching below 15 to 30 cm soil depth

Potential for particle bound transport index = low

Koc - Organic-carbon sorption constant (ml g-1) = 8 (very mobile)

* US EPA = United States Environmental Protection Agency

DT50 = is the time required for the pesticide concentration under defined conditions to decline to 50% of the

amount at application.

Aminopyralid thus displays many similar properties to clopyralid: both are stable in water, are stable to anaerobic

degradation and are highly mobile in the soil. Aminopyralid is rapidly degraded via photolysis under aquatic

conditions, whereas clopyralid is stable to light.

Notably, like clopyralid, aminopyralid appeared to be stable in anaerobic water sediments, which suggests that

biologically-mediated degradation proceeds via aerobically-mediated mechanisms. This is supported by a

statement on behalf of Dow AgroSciences on the Manure Matters web site, 2009: ―Residues in manure break

down if rotovated into the soil and turned frequently‖. This may have implications for materials treated in an

anaerobic digester, such as manures, if the digestate is subsequently applied to sensitive crops.

The main routes of dissipation of aminopyralid appear to be through mineralisation and soil leaching (PMRA,

2007). Aminopyralid appears to be more stable than clopyralid in soil (t1/2 of 103.5 days compared with 25 days,

respectively). Dow themselves have stated that: ―Based on laboratory test guidelines, aminopyralid cannot be

considered as readily biodegradable. However, field studies showed aminopyralid is likely to be non-persistent


systems 19

and relatively immobile‖ (Dow, 2008). The former Pesticides Safety Directorate (now the Chemicals Regulation

Directorate) has suggested that: ―Most of the aminopyralid residue in the soil should have been broken down

after 6 months if the manure been has fully incorporated (rotavated/mixed) into the soil to aid decomposition‖

(Pesticides Safety Directorate, 2008a). As with clopyralid, this suggests that the level of aerobicity in the soil will

affect the rate of degradation. Dow has suggested a period of one year before the soil is aminopyralid-free on

the Manure Matters web site (2009).

5.4 Composting feedstocks There are limited data in the public domain regarding potential concentrations of aminopyralid in feedstocks that

may enter a composting process. Regulatory data submitted in Canada suggests that concentrations were

detected in a number of crops in the parts per million (ppm) range (PMRA, 2007). These are summarised in

Table 7.

Table 7 – Concentrations of aminopyralid in harvested crops in Canada and North America

Crop Application

concentration

Time following

application

Concentration in

harvested crop

(ppm)

Wheat forage 10 g a.e. / ha 0 DAT 0.777

Hay 10 g a.e. / ha 0 DAT 2.377

Wheat grain 10 g a.e. / ha 49 - 56 PHI 0.026

Straw 10 g a.e. / ha 49 - 56 PHI 0.145

Grass forage TIPA salt at ~120 g

a.e./ha

0 DAT 14.03

Grass hay TIPA salt at ~120 g

a.e./ha

0 DAT 51.50

a.e. = acid equivalent: it is the portion of a formulation that can be converted back to the corresponding parent

acid, which is the active herbicide ingredient. It is a term used when a pesticide derivative is used in order to

assess its potential ‗active‘ concentration.

DAT = Day(s) after treatment

PHI = Pre-harvest interval

TIPA = triisopropanolamine

The high concentrations in harvested grass may well present problems if these feedstocks are composted or

digested.

The former Pesticides Safety Directorate also noted that aminopyralid ― ... remains tightly bound to the plant

material until it decomposes‖ (Pesticides Safety Directorate, 2008a) and that when ―manure breaks down it

releases the aminopyralid, which is likely to be at its highest level in the soil about 3 weeks after applying the

manure. However, soil bacteria then break down the aminopyralid so that susceptible plants may start to recover

and grow again.‖ Half-lives of aminopyralid were not quoted.

Ingested aminopyralid is thought to be excreted largely unchanged via the faeces and urine in goats (PMRA

(2007) and cattle (Pesticides Safety Directorate, 2008a), therefore this explains the presumed high levels found in

animal manures, and accounts for the problems experienced by allotment holders in the UK during 2008 (see

Section 6.2).


systems 20

6.0 Compost contamination: an historical perspective

6.1 Clopyralid Unexpected phytotoxic effects of some composts were described in the USA over ten years ago, which were

symptomatic of herbicide activity. Although initially unexplained, further analysis suggested that the effects were

due to clopyralid contaminating commercially-produced composts. Much has been written about this and is

documented on the Internet, so for the sake of brevity a brief history is set out in Table 8.

Table 8 – Summary of compost contamination by clopyralid

Date Documented contamination References

1999 Spokane, Washington, USA

Problems with contaminated compost identified

Symptoms noted on tomato plants grown in containers

Source of contamination identified as grass clippings

Concentrations 31 – 75 ppb detected in compost

Christchurch, New Zealand

Clopyralid detected in compost

Grass clippings identified as source

Bezdicek et al., 2001

CIWMB, 2003

Dow AgroSciences, 2001

Fietje, 2001

Rynk, 2000

2000 Washington State University, USA

Problems with contaminated compost identified, including

the herbicide picloram (an isolated incident)

Clopyralid concentrations from trace to over 200 ppb

detected

Contaminated grass hay and straw identified as the source

Pennsylvania State University

Problems identified during growing trials

Clopyralid at 10 – 75 ppb detected

Incidents in New Jersey also reported

Bezdicek et al., 2001

CIWMB, 2003

Houck and Burkhart, 2001

2001 Dow AgroSciences voluntarily withdrew sales of clopyralid in

Spokane County, WA.

Anon, 2001

2002 Washington State Department of Agriculture (WSDA)

Banned some uses of clopyralid (lawns and turf), except on

golf courses

California State

Restricted clopyralid sale to and use by qualified persons

Oregon State

Clopyralid detected in compost (up to 94 ppb)

Restrictions on clopyralid sales made except in agriculture,

forests, rights of way, cemeteries and golf courses

Anon, 2002

CIWMB, 2003

Musick, 2004

Roberts-Pillon, 2008

Rynk, 2002b

Rynk, 2003

State of Oregon, 2003

WSDA, 2002

2003 Washington State (East)

Increase in clopyralid concentrations in compost reported

Musick, 2004

2008 New Zealand

Clopyralid taken off retail market

Use restricted to agriculture and commercial turf

management

ERMA, 2007

6.1.1 Concentrations detected Initially, analytical test methods for clopyralid were only capable of detecting concentrations above about 50 ppb

(Bezdicek et al., 2001), which is about five-times the concentrations that can affect sensitive plants (below 10

ppb). Test methods therefore required some modification, and clopyralid residues as low as 1 ppb were


systems 21

subsequently detectable. This enabled researchers to identify clopyralid in a number of composts that had

damaged plants (Bezdicek et al., 2001).

Concentrations of clopyralid varied greatly. However, some were found to be well in excess of the levels known

to adversely affect plant growth. For example, in 2001 the Washington State Department of Agriculture (WSDA)

collected samples of feedstocks and finished compost, spanning a range of composting methods and feedstocks.

In one instance a concentration of 1,550 ppb clopyralid was detected in grass clippings, and 477 ppb in immature

compost (Rynk, 2002a).

Following the ban on the use of clopyralid for use on lawns and turf in Washington State in 2002, samples of

composts tested on behalf of WSDA showed a decrease in clopyralid concentrations in compost (by up to 80%),

suggesting the ban had had an effect (WSDA, 2004). In a similar move, the Oregon Department of Agriculture

reported a drop of 47% between 2003 and 2004 in clopyralid concentrations in Oregon‘s compost, although two

facilities did, unexpectedly, show an increase (Musick, 2004 and Roberts-Pillon, 2008).

It has been suggested that clopyralid contamination was more widespread than research data reported, because

many composting operations were not routinely testing for the herbicide (Dan Caldwell, Personal

Communication).

6.1.2 The situation in Washington State, USA The problems at Spokane in eastern Washington State, USA, were first identified in commercially-grown

tomatoes, raised in a glass house in 100% compost, in contrast to the problems at Pullman (also in Washington

State), which were identified outdoors following the application of compost to gardens (Rynk, 2000).

Spokane residents were served by a green waste kerbside collection scheme, which had a high participation rate.

Properties were characterised by a large proportion of lawns that were managed under professional contracts and

treated with Confront (a mixture of clopyralid and triclopyr sold by Dow AgroSciences). Clopyralid was used

heavily in the Spokane area; amounts were much greater than in other areas of Washington State (Rynk, 2002a,

Dow AgroSciences, 2001 and Dan Caldwell, Personal Communication).

It appeared that grass clippings were the principal feedstocks of concern (Rynk, 2003). Dow AgroSciences have

suggested that grass contributed up to 85% of the feedstocks at the Spokane composting facility (Dow

AgroSciences, 2001), and estimates by the former manager of two compositing sites in western Washington State

estimated that during the Spring grass volumes well above 50% by volume (over 80% by weight leading to

concentrations of between 70 to 150 ppb in the feedstocks) were received (Jeff Gage, Personal Communication).

In response to reported problems associated with clopyralid in the USA, Dow AgroSciences issued a paper

‗Clopyralid and Compost‘ in 2001 (Dow AgroSciences, 2001). They suggested that a number of factors came

together in Spokane that would not be expected to occur elsewhere; they stated that composting grass clippings

treated with Confront was off-label, and reiterated the need to follow the instructions on the label. However, the

US Composting Council (USCC) pointed out that the supply chain of compost feedstocks involves a number of

different parties, making it difficult to ensure that feedstocks aren‘t contaminated (Rynk, 2001), and have

stressed the need for effective and consistent communications among all participants.

The increase in clopyralid concentrations observed in Eastern Washington State suggested that labelling was not

the whole answer, as some contamination came from agricultural sources (Musick, 2004). Indeed, it has been

suggested that some Washington facilities have recently (in 2009) experienced contamination stemming from

animal feeds and straw for bedding (used as compost feedstocks), even with supplier contracts that stipulate no

clopyralid herbicide use in the crops. This has been enough to halt the sale of composts occasionally (Jeff Gage,

Personal Communication).

These problems indicate that voluntary controls and stewardship responsibilities by end users may not be

sufficient to prevent contamination arising. In a 2001 opinion article, Gabriella Uhlar-Heffner clearly stated that

responsibility should lie with manufacturers of the herbicide (Uhlar-Heffner, 2001). Based on these observations,

any risk management procedures adopted for the UK need to take account of unofficial off-label uses in both

amateur and professional applications.


systems 22

6.2 Aminopyralid Problems associated with the use of aminopyralid were reported in June 2008 in the UK, after allotment holders

experienced damage to sensitive plants following manure application (Davies, 2008 and RHS, 2008). This

appears to have been sourced from animals grazed on pastures or grassland previously treated with

aminopyralid-containing products, such as Forefront or Pharaoh (Manure Matters web site, 2009 and Pesticides

Safety Directorate, 2008a). Dow AgroSciences has suggested that the problems stemmed from farmers ignoring

label warnings about the management of manures, rather than inappropriate off-label application of aminopyralid

per se (Anne Thompson, Dow AgroSciences, Personal Communication). The unit price of aminopyralid was

probably sufficiently high to prevent casual off-label use.

In response to these problems and the high level of associated media attention, Dow AgroSciences voluntarily

requested that aminopyralid‘s approval be suspended. This was brought into effect on 24 July 2008 (Pesticides

Safety Directorate, 2008b).

Unfortunately, there has not been the level of reported research into this problem compared with the scrutiny

applied to clopyralid in the USA, therefore it has not been possible to ascertain the extent nor levels of

contamination experienced. Dow AgroSciences has stated that levels of aminopyralid in farm yard manures of

between 0.08 ppm to 0.48 ppm (80 to 480 ppb) were detected, whilst slurry concentrations of between < 0.01

ppm (Limit of Quantification) up to 0.19 ppm (10 to 190 ppb) were detected (Anne Thompson, Dow

AgroSciences, Personal Communication).

The Advisory Committee on Pesticides reviewed the suspension of aminopyralid during summer 2009. Nine

products containing aminopyralid (either singly or in conjunction with fluroxypyr or triclopyr) were subsequently

approved (November 2009; Table 12), subject to restricted use (compared with the previous products) and

increased stewardship. Products may be used either to:

Control a range of weeds on grassland for grazing (silage making or hay harvesting is not permitted

within one year following application). Products may only be applied to grassland on which cattle or

sheep (and not horses) may graze. The aim is to: ―prevent sale of manure from treated grassland being

supplied to gardeners and allotment holders, eliminating the risks involved‖ (Chemicals Regulation

Directorate, 2009). The restrictions will also mean that most of the manure produced will remain on the

treated grassland; manures collected when animals are housed (for example in milking parlours) may

only be spread onto grassland and must remain on the farm of origin; and

Control pernicious or invasive weeds in amenity situations. It must not be used on land where

vegetation will be cut for animal feed, fodder or bedding nor for composting or mulching within one year

of treatment. Additionally, it may not be used on land that will be grazed by livestock.

Notably, potential purchasers of aminopyralid must be trained by a British Agrochemicals Standards Inspection

Scheme (BASIS) certified advisor so that they are made aware of the potential risks, and checks will be made on

the proposed use.

6.3 Picloram Picloram is a pyridine herbicide, which is chemically similar and has similar modes of action to clopyralid and

aminopyralid. It is used to control the growth of woody plants, although it is also used to control a number of

broadleaved weeds.

Picloram was identified as the problematic herbicide in many of the situations experienced in Washington State

(Bezdicek et al., 2001), and apparently, more recently in North Carolina and perhaps Virginia (R. Rynk, Personal

Communication). Composts contaminated with picloram have not been reported in the literature in the UK to

date.

Sixteen products containing picloram as an active ingredient are licensed in the UK for professional use only, and

are listed in Table 14. Seven of these formulations also contain clopyralid. Picloram is used on oil seed rape

(winter) and land not intended for cropping. Agricultural residuals, including manures, may therefore represent

sources of this herbicide for composting or anaerobic digestion.

Research carried out by the Recycled Organics Unit in Australia suggested that picloram does not degrade during

the composting process (Recycled Organics Unit, 2007a).


systems 23

7.0 Compost testing and bioassays Testing composts in laboratories for low concentrations of herbicides is methodologically problematic, due to the

heterogeneous nature of the substrate, the presence of humic substances etc. (Recycled Organics Unit, 2007a).

As noted previously, laboratory test procedures were initially only able to detect clopyralid concentrations above

about 50 ppb (Bezdicek et al., 2001). Notwithstanding, analytical test methods are costly to perform and may

not provide a true picture of the bioavailability of the herbicide to plants. In the USA research by King County

and the City of Seattle in Washington State (King County, 2002) found that there was a wide variability in

analytical test results and bioassays.

Following reported problems in Washington State, USA, Washington State University published a bioassay test

method for gardeners and researchers to use (WSU, 2002). This adopted a two tier approach, describing a

simple test method for gardeners using peas, and a more scientifically robust method for researchers, which

involved employing a number of the USCC‘s Test Methods for the Examination of Composting and Compost.

Clopyralid damage of garden peas (variety not specified) was scored by referring to reference photographs as:

0 = ―No symptoms‖ – Leaves lie flat before opening. Leaves do not cup or curl upward at all.

1 = ―Slight damage‖ - Leaves of new growth are somewhat cupped. Leaves do not lie flat before

opening.

2 = ―Moderate damage‖ – Leaves are obviously cupped.

3 = ―Severe damage‖ – Most leaves are cupped. Stems are twisted.

However, the WSU bioassay employed high rates of compost, and the effects of other phytotoxic factors, such as

salinity (electrical conductivity) could not be disaggregated. Brinton et al. (2005 and 2006) investigated the

effects of electrical conductivity of composts on the growth of red clover (sensitive to clopyralid) and peas

(moderately sensitive to clopyralid). They found that by adjusting the quantity of compost in the test medium to

adjust for the level of electrical conductivity this allowed the effects of herbicide to be better identified. Notably,

this is similar to the bioassay specified in the UK‘s BSI PAS 100: 2005, which stipulates that compost samples be

diluted with sphagnum peat to obtain an electrical conductivity of 300 µS cm-1 (which is ten-times less than that

specified by Brinton) before testing using tomato plants.

Brinton et al., 2005 recommended the use of red clover (Trifolium pratense), which enabled phytotoxic effects at

low clopyralid concentrations to be detected. Similarly, the Recycled Organics Unit in New South Wales,

Australia, also developed a bioassay using red clover, as this plant produced observable effects at concentrations

as low as 1 – 2 ppb, and produced results within 14 days (Recycled Organics Unit, 2007c). (The PAS 100

bioassay method using tomatoes takes 28 days.)

Reference photos of auxin-like herbicide damage to red clover (Trifolium pratense) are available on-line, such as

those published by the Recycled Organics Unit in New South Wales, Australia (Recycled Organics Unit web site).

In the UK, Dow AgroSciences have suggested a simple bioassay for allotment holders and gardeners to use on its

manure matters web site. This involves a 50:50 mix of manure with multi-purpose compost and growing broad

beans as the test plant (variety not specified). It seems likely that this method would be susceptible to the

salinity issues discussed by Brinton et al., as well as phytotoxic effects due to high nutrients and substrate

instability.

It is recommended that the method described by either Brinton et al., or the Recycled Organics Unit (2007c) be

employed if clopyralid and/or aminopyralid damage is suspected.

8.0 Effects of clopyralid and aminopyralid on plant growth 8.1 Application issues There is a paucity of data in the public domain on the effects of clopyralid and aminopyralid on crops, dispersal

and degradation rates. The reports identified in the literature search are summarised below.

8.2 Effect of clopyralid on crop rotation Field-scale research looked into the effect of clopyralid applied at 70 to 560 g ae ha-1 (to wheat) and carryover in

the soil to crops planted a year after. Flax, potato, and safflower were not affected, however, growth of

sunflowers (at 280 and 560 g ha-1 clopyralid) and soybeans (at 560 g ha-1 clopyralid) were curtailed (exhibited in

reduced numbers of sunflower heads and yield, and reduced soybean height, stand and yield; Thorsness and


systems 24

Messersmith, 1991). The authors concluded that application rates of 280 g ha-1 or less, in silty clay, clay loam,

and silty clay loam soils would not affect crops sown 11 months or later3.

8.3 Translocation in Canada thistle and biological activity Bukun et al., (2009) investigated the translocation of both aminopyralid and clopyralid in Canada thistle (Cirsium

arvense; known in the UK as creeping thistle). They found that clopyralid was more readily absorbed by the test

plants and more readily translocated out leaf area where it was applied than aminopyralid. They also found that

more of the clopyralid translocated to above ground parts than in the roots, unlike aminopyralid which was found

at similar concentrations in above ground tissue and roots. Neither aminopyralid nor clopyralid were metabolised

by the plants eight days after treatment. The researchers suggest that aminopyralid has a greater biological

activity than clopyralid.

8.4 Translocation into tree leaves The contamination identified at Penn State University included fallen tree leaves vacuumed from the University‘s

lawns. In an attempt to ascertain whether clopyralid was translocated through the tree and was the source of

contamination, leaves from Elm, Oak and Maple trees in the campus grounds were handpicked and assayed for

clopyralid. In all samples, clopyralid could not be detected, suggesting that the herbicide was not translocated

through the tree and into the leaves (Burkhart and Davitt, 2002). However, although the leaves themselves were

eliminated as the source of contamination, that act of vacuum collection resulted in co-collection of treated grass.

This highlights the need for vigilance, as cross-contamination of clopyralid between feedstocks may occur.

8.5 Enclosed growing of crops in polytunnels and glasshouses Researchers at Penn State University (Burkhart and Davitt, 2002) investigated the effect of compost containing

clopyralid application in polytunnels. They observed that clopyralid could persist for more than two years under a

polytunnel. The authors suggested that clopyralid‘s persistence in polytunnels may be due to reduced moisture

content in soils (due to lack of natural precipitation and conservation of water due to irrigation methods), thereby

reducing soil microbial activity, bioavailability of the pesticide in the liquid-solid interface and reduced leaching

from the root zone. The authors suggested that organic matter may affect the solubility of clopyralid, with more

water required at greater organic matter levels to bring clopyralid into solution.

The researchers at Penn State University also noted that symptoms of clopyralid were only observed about four

weeks after transplanting crops (bell peppers) from glasshouse to field (Houck and Burkhart, 2001). This may

have been due changes in soil / substrate moisture levels, as a ‗wet / dry cycle‘ was thought to release clopyralid.

8.6 Rainfall The areas in eastern Washington State that were most plagued by clopyralid (and picloram) are dry climates

(Spokane, Pullman and the interior hay-producing regions). Although Western Washington State is moist it

obtains much of its manure feedstock from the dry region east of the mountains, and the compost is largely used

in the summer season, which is dry even on the west side. Being generally water soluble, sparse rainfall seems

to be a common element in at least some of the problem areas associated with these chemicals i.e. in regard to

the source of feedstocks, composting location and where the compost product is used. The effect of rainfall

throughout the cycle is a factor in the fate of these chemicals that seems to be overlooked in the literature.

The two key factors affecting clopyralid activity thus appear to be soil moisture and organic matter content. Crops grown in protective environments may therefore merit special attention.

8.7 Compost application rates Researchers at Washington State University (Cogger et al., 2002) investigated the effects of clopyralid containing

compost at high concentrations (82 ppb) and low (12 ppb) on the growth of tomatoes (three varieties), one

tomatillo, peas and beans. They applied compost to soil at two rates (1 and 3 inches depth of compost applied to

the soil surface before tilling), and incorporated the compost to a depth of six inches with a garden tiller. The

type of soil, and, in particular its organic matter content, was not disclosed. The test results suggested that only

at the high application rate (3 inches) in the high concentration compost were effects of clopyralid noted. The

plants appeared to grow normally at the lower application rates and with the lower clopyralid levels (high and low

application rates). Although this study was not scientifically rigorous, it does indicate that incorporating

3 UK application rates of clopyralid vary depending upon the crops to which it is applied. The maximum permitted annual rate of application of Dow Shield (18.02% w/w clopyralid as the monoethanolamine salt) is 400 g / ha.


systems 25

contaminated compost into soil could reduce the effects of clopyralid sufficiently to permit the growth of sensitive

plants.

Similar suggestions were also made by Woods End Laboratories (Brinton and Evans, 2002), who predicted that

crops grown in soils to which contaminated compost had been incorporated up to a depth of six inches, would

only occur at highly contaminated compost at high application rates and to crops such as peas, sunflower and

clover which are highly sensitive to clopyralid.

9.0 Managing the risks The UK composting sector has benefitted from the introduction of the (former) Composting Association‘s

standards and certification scheme in 2000, which, in conjunction with WRAP, led to the introduction of the BSI

PAS 100 specification for composted materials in 2002. These have been updated and superseded by a 2005

edition (BSI PAS 100:2005), augmented with the Compost Quality Protocol (CQP) in England and Wales in 2007

(WRAP and Environment Agency, 2007), and, more latterly, will be superseded again in 2010 by a new edition.

Collectively, these documents and the associated third-party certification scheme (now overseen but not run by

the Association for Organics Recycling) have required compost producers to implement a comprehensive Quality

Management System (QMS), coupled with an obligatory Hazard Analysis Critical Control Point (HACCP)

assessment. These set in place systems of control at every certified composting site, in contrast to the USA,

which does not have a nationally-based certification scheme of this sort.

Notably, the PAS 100 and the CQP mandate that an audit trail be maintained by the compost producer

throughout the composting process and that samples of compost routinely be tested at accredited laboratories for

contaminants and for phytotoxicity through a plant bioassay. A number of these principles have been suggested

by the Recycled Organics Unit in New South Wales, Australia, in developing its Risk Management Tools for the

Recycled Organics Industry (Recycled Organics Unit, 2007c).

A number of factors relating specifically to clopyralid contamination are discussed below.

As aminopyralid is now only licensed for use by professional users and is restricted to either grazing ground for

sheep and cattle (not horses) or amenity grassland to control invasive and pernicious weeds, the risks to

composting operations associated with its use have been significantly reduced. However, compost site operators

should be made aware that the compound is licensed for use in these applications and not accept feedstocks

from these sources when there is any doubt over their quality.

9.1 Composting feedstocks Pesticides, including clopyralid, may enter composting feedstocks from a variety of diffuse (non-point) sources.

This creates difficulties for composting site operators, especially when implementing their HACCP procedures.

The feedstocks of concern are detailed below in Table 9. Grass and animal manures (including animal feeds such

hay, silage, fodder crops, and animal bedding) present the greatest risk of clopyralid contamination.


systems 26

Table 9 – Composting feedstocks and their potential to be contaminated with clopyralid

Feedstock type Feedstock source Potential for contamination

Green waste (mixed) Municipal - household

(kerbside or HWRC

collection)

Variable.

Amateur use of clopyralid is only licensed for use on lawns

by householders.

It is likely that clopyralid contaminated grass would be

diluted by other green wastes in compost feedstocks,

although this may be less pronounced at certain times of

the year (e.g. late spring and summer when larger volumes

of grass clippings are composted [see Appendix 2]).

Additionally, due to its effect on certain plant species at

very low concentrations, dilution cannot be relied on as a

mitigation measure.

Composting at home of clopyralid contaminated materials

may be problematic, although this will be limited to

individual gardens depending on herbicide use.

Green waste (mixed) Municipal (non-household)

and non-municipal

Variable – possibly greater than household sources.

Greatest risk would be from grass clippings on

professionally managed lawns (e.g. golf courses) and

landscaped areas. However, the proportions of grass

clippings sent for commercial composting by landscapers

and other professional users are currently unknown,

although it is likely that the majority of such clippings will

remain at the site of production.

Contracts of Supply between compost site operators and

feedstock suppliers could address this issue, thereby

minimising risk.

Leaves and woody

wastes

Municipal - household Low, as clopyralid does not appear to transfer to woody

plant material, however, cross contamination from treated

grass has been documented.

Leaves and woody

wastes

Municipal (non-household)

and non-municipal

Variable – this will depend upon whether this material is

sourced from areas where clopyralid has been applied to

grass / turf. Contracts of supply would be helpful for this

scenario.

Crop by-products Agriculture Low to high, depending upon the feedstock crop.

Where crop residuals are composted on-farm and the

composted materials re-applied to the farmer‘s own land,

the farmer (or appointed third-party) can track feedstock

materials and ensure that the resulting compost is not

applied to sensitive crops.

Manures, including

straw and hay

All sources High risk.

Clopyralid is used principally on grassland and on crops

used as animal feed and fodder (Table 3). As clopyralid

passes through grazing animals unchanged, there is

potential for it to be ‗concentrated‘ in the faeces and urine.

Significant problems associated with manures have been

observed in the USA and in the UK (with aminopyralid).


systems 27

A literature review of the composition of garden waste collected for biological treatment is detailed in Appendix 2,

indicating a paucity of data. Grass clippings were, in general, found in the greatest proportions during the spring

and summer months, which coincides with the on-label use of lawn care products containing the herbicide

clopyralid. In one study (Morpeth, Northumberland) over 60% of the total garden waste collected in wheeled

bins was grass during May to September (1995/96).

Data on green waste compositions stemming from professional users (e.g. landscapers and lawn care specialists)

sent for commercial composting were not available.

In order to gain a better understanding of the potential risks associated with contaminants (e.g. clopyralid) that

may enter a commercial composting system through garden wastes, a better understanding of garden waste

composition and variation would be beneficial. This would need to accommodate differing collection systems

(bring and kerbside), housing types and local policies for residual waste collection.

9.2 Compost use

9.2.1 Agriculture and field horticulture It is hard to predict how long clopyralid residues will remain in the soil following either direct application of the

herbicide, or indirectly through contaminated compost. Soil organic matter, moisture, soil temperature and the

level of aerobicity (which will be dependent upon soil type) appear to be the main factors affecting dissipation

and degradation.

As most compost applied to fields would be ploughed prior to planting crops, it seems likely that potential

contamination would present a minimal risk (see, for example, Brinton and Evans, 2002), assuming the upstream

controls during processing and sourcing feedstocks (discussed above) are implemented. The potential for

problems could be highlighted in the compost producer‘s contract of supply, in particular, if contamination is

suspected. In this case, instructions based on the labelling requirements for clopyralid use could be followed.

Compost may also be used as a mulch in the growth of soft fruit (such as strawberries) and top fruit (see, for

example, Lock et al., 2008). It is not thought that clopyralid will translocate through trees into leaves (Burkhart

and Davitt, 2002), however, as its effects on top fruit production have not been documented, further research

would be beneficial. Clopyralid is licensed for use on strawberries, therefore it is not envisaged that restrictions

on compost use on this crop are warranted.

9.2.2 Growing media and protected crops Plants grown in containers and under protective cover (e.g. polytunnels) appear to be the most susceptible to

potential clopyralid contamination, due to the high levels of organic matter in the growth substrate, and the lower

rates of irrigation. The Guidelines for the Specification of Composted Green Materials used as a Growing Medium

Component (Waller, 2004) suggest that composted green material be incorporated up to a maximum of 33% by

volume with other suitable low nutrient substrates.

It is recommended that the Growing Media Specification be adhered to for all compost sold for use in either

growing media or protected crops. Additional bioassay testing of compost batches destined for incorporation into

growing media may provide assurance to growing media manufacturers, in particular at times of the year when

grass clippings would be at their greatest in compost feedstocks.

9.2.3 Landscaping and grounds maintenance Clopyralid is widely used on grass and turf in these sectors. There are popular landscape plants within the

Asteraceae family, including sunflowers, marigolds and dahlias that are used in these settings, therefore

landscapers and grounds maintenance professionals should be made aware of any suspected contamination

problems.


systems 28

10.0 Recommendations The predominant factor with clopyralid (and similar chemicals) in compost is not its rate of decomposition. In

general, clopyralid seems to decompose fairly well in the typical time frame of a composting process (although

the Australian studies apparently suggest otherwise). The dominant factor is concentration. Clopyralid (and like

chemicals) simply remain potent at very low concentrations, even after the original concentration decreases

substantially during composting (e.g. 99%).

The second dominant factor is the ultimate use of the compost. Clopyralid remains potent for only a few families

of plants; which unfortunately include important and popular food and landscape crops. High concentrations of

clopyralid in compost will go unnoticed for the many uses/plants for which clopyralid is quite acceptable.

Hence, ―clopyralid in compost‖ is a story about ―concentration and coincidence‖: Concentration because of

clopyralid potency at very low concentrations (and that of like products); coincidence because tainted compost

must coincide with particular uses to become a problem. Another important coincidence is that it takes a

somewhat unlikely combination of similar feedstocks, similarly treated with clopyralid, to establish a troublesome

clopyralid concentration to begin with. In most composting situations the feedstocks are diverse and/or come

from dispersed sources that do not have the same patterns of pesticide use. Important exceptions to this typical

situation occur, exemplified by the experience in Spokane, Washington State and by the use of ―single-source‖

feedstocks (e.g. manure obtained from one or two farms).

This review has provided background information to assist compost producers and end users in understanding

the sources and fate of clopyralid contamination. However, it has not provided a quantitative risk assessment,

and the potential for harm to plants from contaminated compost will depend upon a range of variables, such as

feedstock types, time of year, composting duration etc. Further research could usefully be undertaken to

quantify the risks of these products adversely affecting the UK composting sector, and we suggest that WRAP

and the composting industry engage with the manufacturers of clopyralid to identify an appropriate programme

of work.

Based on the information gathered during this study, we have set out a number of recommendations below

aimed at either preventing or reducing the risk of problems arising.

10.1 Municipal wastes There are a number of clopyralid-containing herbicide products available for amateur use (see Table 10) in the

UK. The extent to which contaminated grass (or other green wastes) entering a commercial composting facility

through a municipal waste collection service could create problems is unknown at present, however, the most

robust long term strategy to ensure compost quality is to eliminate the potential for contamination to occur at

source. As long as these products are sold for amateur use, the onus should therefore remain on herbicide

manufacturers to provide clear, practical advice to householders for recycling grass and other garden wastes

following herbicide application. This may include encouraging the practice of ―grasscycling4‖, where clippings are

left on the lawn, rather than removed during mowing.

The challenges faced by local authorities in meeting their targets to divert biodegradable municipal waste from

landfill should not be underestimated; hence disposal of grass or other green wastes in residual (mixed or ‗black

bag‘) waste collections should not be encouraged.

10.2 Compost manufacturers The extent to which compost manufacturers can control clopyralid contamination and ameliorate its effects is

limited. We therefore recommend that compost site operators:

Remain vigilant to the potential for clopyralid contamination during late spring and summer when the

input of grass clippings is likely to be at its greatest, and ensure that this is adequately addressed in

HACCP plans (where appropriate);

Communicate with suppliers of feedstocks to highlight the potential for contamination through the use of

clopyralid-containing herbicides. (This is particularly important where ―single source‖ feedstocks are

composted. Mixing feedstocks of different types or from different sources will lower the risk of starting

with a high concentration of clopyralid, and therefore ending up with unacceptably high concentrations.)

4 This practice has been widely adopted and promoted in the USA.


systems 29

This may take the form of a Contract of Supply with landscapers, grounds maintenance and sports turf

professionals to highlight the potential for contamination, and ensure, as far as reasonably practicable,

that feedstocks are not delivered for composting within a year of clopyralid application. A leaflet

explaining the risks and safe management of treated feedstocks could be developed; it is envisaged that

this could be handed to professionals when they deliver feedstocks to a composting site at the

weighbridge when waste transfer notes and other receipts are exchanged. These initiatives could

usefully be achieved through a joint exercise between with the manufacturers of clopyralid, WRAP and

the composting industry;

Consider increasing the frequency of bioassay testing for composts intended for use in growing media or

to raise protected crops, however, it is acknowledged that this will entail additional costs;

Where there is any doubt over their source, ensure that composted animal manures are sent for use in

non-sensitive applications. This could be addressed through a contract of supply (which already exists

for agricultural and field horticultural crops through the Compost Quality Protocol in England and Wales).

As a matter of course, compost producers should make their customers aware of the suitability of their

composts for different end uses; and

Adhere to the Growing Media Specification for all compost sold for use in either growing media or

protected crops.

Should clopyralid contamination be suspected, composts can still be used in a range of applications, such as: turf

topdressing, corn and cereal grains, soil amendment (where the compost is incorporated into soil used to grow

non-legume field crops) and topsoil manufacture. If clopyralid contamination is suspected, then crops and

applications to avoid include: growing media, growing beds under covers or in greenhouses, home vegetable

gardens and legumes.

10.3 Compost testing The BSI PAS 100 and the CQP require periodic testing of compost (at least once every 5000 m3 in PAS100:2005),

including the use of a plant bioassay which uses tomato as the indicator plant. Tomato is sensitive to low

concentrations of clopyralid (<1 ppb; Bezdicek et al., 2002). Based on experiences in the USA, plant bioassays

were shown to be the most appropriate test method for the routine evaluation of potential herbicide

contamination in composted materials, due to the cost and complexity of laboratory chemical analysis (see

Section 7.0). Brinton et al., 2005, and the Recycled Organics Unit, 2007c, however, suggested employing red

clover (Trifolium pratense) in place of tomato (Solanum esculentum).

Chapman et al., (2009) have recently reviewed the plant bioassay test method as specified in UK‘s PAS 100

specification against methods used elsewhere in the world. They concluded that the method specified in PAS 100

should be retained, but that additional validation be carried out. We also recommend that the existing PAS 100

bioassay be validated:

Using compost containing concentrations of clopyralid known to adversely affect plant growth;

Against red clover (Trifolium pratense), as this has a high degree of sensitivity to clopyralid and ability to

produce observable results after 14 days; and

Against the test methods described by Brinton et al., 2005, and the Recycled Organics Unit, 2007c, as

these were developed specifically to identify low concentrations of herbicide in the growing medium.


systems 30

11.0 References

Abramović, B.F., Anderluh, V.B., Šojić, D.V. and Gaál, F.F. (2007) Photocatalytic removal of the herbicide clopyralid

from water J. Serb. Chem. Soc. 72 (12): 1477–1486.

AEA Technology (2000) Monitoring the Production of Compost from Wastes on a Continuous Basis. Environment

Agency R&D Technical Report P355, pub. WRc, Swindon

Ahmad, R., James, T.K., Rahman, A. and Holland, P.T. (2003) Dissipation of the Herbicide Clopyralid in an

Allophanic Soil: Laboratory and Field Studies Journal of Environmental Science and Health Part B—Pesticides, Food

Contaminants, and Agricultural Wastes B38 (6): 683–695.

Aminopyralid. Pesticide Properties Database, University of Hertfordshire.

http://sitem.herts.ac.uk/aeru/iupac/Reports/29.htm [Accessed 16 July 2009]

Anon (2001) Chemical Company Pulls Herbicide Off Spokane Shelves BioCycle June: 6.

Anon (2002) California Regulators Act to Protect Compost from Herbicide. BioCycle April: 6-10

Association for Organics Recycling web site. www.organics-recycling.org.uk [Accessed 23 June 2009]

Auxin-Type Herbicide Bioassay Reference Photos. Recycled Organics Unit Web site:

http://www.recycledorganics.com/processing/risk/photos.htm [Accessed 16 June 2009]

Bezdicek, D., Fauci, M. Caldwell, D. and Finch, R. (2002) Proceedings of the International Symposium Composting

and Compost Utilization 933-939. Eds. Frederick C. Michel, Jr. Robert F. Rynk and Harry A. J. Hoitink.

Bezdicek, D., Fauci, M., Caldwell, D., Finch, R. and Lang, J. (2001). Persistent herbicides in compost. BioCycle

42(7), 25-30.

Boldrin, A. and Christensen, T.H. (2010) Seasonal generation and composition of garden waste in Aarhus

(Denmark) Waste Management 30, 551–557.

Brinton, W.F. and Blewett, T.C. (2004) Presence, Fate, and Effects of Clopyralid and Other Anthropogenic Residues

in Green Waste Composting. Paper 4A-21, in: A.R. Gavaskar and A.S.C. Chen (Eds.), Remediation of Chlorinated

and Recalcitrant Compounds—2004. Proceedings of the Fourth International Conference on Remediation of

Chlorinated and Recalcitrant Compounds (Monterey, CA; May 2004). ISBN 1-57477-145-0, published by Battelle

Press, Columbus, OH, www.battelle.org/bookstore.

Brinton, W.F. and Evans, E. (2002) Herbicides in Compost: Potential Effects on Plants. Composting News April: 1-2.

Brinton, W.F., Evans, E. and Blewett T.C. (2005) Herbicide Residues in Composts: pH and Salinity Affect the Growth

of Bioassay Plants. Bull. Environ. Contam. Toxicol. 75:929-936

Brinton, W.F., Evans, E. and Blewett T.C. (2006) Reliability of Bioassay Tests to Indicate Herbicide Residues in

Compost of Varying Salinity and Herbicide Levels. Compost Science and Utilization 14 (4): 244-251.

British Standards Institution (2005) Specification for Composted Material Publicly Available Specification 100. ISBN

0-580-45195-X.

Bukun, B., Gaines, T.A., Nissen, S.J., Westra, P., Brunk, G., Shaner, D.L., Sleugh, B.B. and Peterson, V.F. (2009)

Aminopyralid and Clopyralid Absorption and Translocation in Canada Thistle (Cirsium arvense). Weed Science 2009

57:10–15

Burkhart, E.P. and Davitt, N.H. (2002) Herbicide Persistence in Finished Compost Products: A Case Study from Penn

State. Proceedings of the International Symposium Composting and Compost Utilization 940-953. Eds. Frederick C.

Michel, Jr. Robert F. Rynk and Harry A. J. Hoitink.

Büyüksönmez, F., Rynk, R., Hess, T.F. and Bechinski, E. (1999). Occurrence, degradation and fate of pesticides

during composting. Part I: Composting, pesticides and pesticide degradation. Compost Science and Utilization, 7(4):

66-82.

Büyüksönmez, F., Rynk, R., Hess, T.F. and Bechinski, E. (2000). Occurrence, degradation and fate of pesticides

during composting. Part II: Occurrence and fate of pesticides in compost and composting systems. Compost

Science and Utilization, 8(1): 61-81.

California Integrated Waste Management Board web site (2003) Clopyralid in Compost and Mulch.

http://www.ciwmb.ca.gov/Organics/Threats/Clopyralid/Background.htm Updated 14 October 2003 [Accessed 30

June 2009]

http://sitem.herts.ac.uk/aeru/iupac/Reports/29.htm

http://www.organics-recycling.org.uk/

http://www.recycledorganics.com/processing/risk/photos.htm

http://www.ciwmb.ca.gov/Organics/Threats/Clopyralid/Background.htm


systems 31

Chapman, A. Merrington, G. and Crane, M. (2009) Review of the plant growth and weed propagule tests used in the pas100 specification for quality compost (WRAP Project TYR009-19. Report prepared by WCA environment Ltd on behalf of WRAP, Banbury, Oxon, UK)

Chemicals Regulation Directorate (2009) Regulatory Update 32/2009 Issued 6 October 2009. Accessed at

http://www.pesticides.gov.uk/

Chemicals Regulation Directorate web site. http://www.pesticides.gov.uk/ [Accessed June 2009]

Clopyralid. Pesticide Properties Database, University of Hertfordshire.

http://sitem.herts.ac.uk/aeru/iupac/Reports/169.htm [Accessed 16 July 2009]

Cogger, C., Bary, A. and Myhre, E. (2002) Clopyralid: Garden Demonstration Plots. Washington State University

Information Sheet accessed at: http://www.puyallup.wsu.edu/soilmgmt/Pubs/Paper_Clo_Garden.pdf

Cox, L., Walker, A. Hermosin, M.C. and Cornejo, J. (1996) Measurement and simulation of the movement of

thiazafluron, clopyralid and metamitron in soil columns. Weed Research 36: 419–429.

Davey, A., Clist, S. and Godley, A. (2009) Home Composting Diversion: Household Level Analysis. Project EVA075-

001. Waste and Resources Action Programme, Banbury.

Davies, C. (2008) Home-Grown Veg Ruined By Toxic Herbicide. The Observer, 29 June 2008 and published online

at: www.guardian.co.uk on 29 June 2008. Updated on 17 July 2008.

Dow (2008) Product Safety Assessment Aminopyralid, The Dow Chemical Company Form No. 233-00376-MM-0308

Dow AgroSciences (1998) Clopyralid a North American Technical Profile, Dow AgroSciences.

Dow AgroSciences (2001) Clopyralid and Compost.

Environmental Risk Management Authority New Zealand (2007) Clopyralid Herbicide To Be Taken Off The Retail

Market. Media Release (20 August 2007). Accessed at: www.ermanz.govt.nz

Fietje, G. (2001) New Zealand City Confronts Contamination. BioCycle July: 31.

Fogarty, A.M. & Tuovinen, O.H. (1991) Microbiological Degradation of Pesticides in Yard Waste Composting.

Microbiological Reviews, 55 (2): 225-233.

HDRA & The Open University (1999) Full scale composting experiments at Morpeth. Environment Agency R&D

Technical Report P314, pub. WRc, Swindon.

Houck, N.J. and Burkhart, E.P. (2001) Penn State Research Uncovers Clopyralid In Compost BioCycle July: 32-33.

King County Solid Waste Division and Seattle Public Utilities (2002) Clopyralid Sampling and Testing Report.

Accessed online at: http://your.kingcounty.gov/solidwaste/soils/documents/KCSPUClopyralidTestingReport.pdf

Krogmann, U. (1999) Effects of season and population density on source-separated waste composts. Waste

Management & Research 17, 109-123.

Lock, D., Lopez-Real, J., Green, M., Saunders, G. and Wallace, P. (2008) PAS 100 compost applied as a mulch in

top fruit (WRAP Project OAV011-010) WRAP, Banbury.

Lubytė, J.D., Danutė, J., Antanaitis, S. and Antanaitis, A. (2007) Decomposition of chlopiralid [sic], tribenuron-

methyl and pendimethalin in different organic substrates. Ekologija 53 (4): 77–83.

Macaulay Land Use Research Institute (2009) Risk Assessment of Application of Composted Wastes to Land (WRAP

Project OAV021-004) WRAP, Banbury.

Manure Matters web site. www.manurematters.co.uk. [Accessed on 25 June 2009]

Miltner, E., Bary, A. and Cogger, C. (2003) Clopyralid and Compost: Mowing Effects on Herbicide Content of Grass

Clippings. Compost Science and Utilisation 11(4): 289-299.

Musick, M. (2004) Clopyralid Levels Decline, But Controversy Continues. BioCycle May 45 (5): 52-53.

Pest Management Regulatory Agency, Health Canada (2007) Aminopyralid Regulatory Note REG2007-01. ISBN:

978-0-662-44841-9 (978-0-662-44842-6) Catalogue number: H113-7/2007-1E (H113-7/2007-1E-PDF) www.pmra-

arla.gc.ca

Pesticides Safety Directorate (2008a) Regulatory Update 18/2008 Issued 11 July 2008 Accessed at




http://www.puyallup.wsu.edu/soilmgmt/Pubs/Paper_Clo_Garden.pdf

http://www.guardian.co.uk/

http://www.ermanz.govt.nz/

http://your.kingcounty.gov/solidwaste/soils/documents/KCSPUClopyralidTestingReport.pdf

http://www.manurematters.co.uk/



systems 32

Pesticides Safety Directorate (2008b) Regulatory Update 23/2008 Issued 24 July 2008 Accessed at


Pesticides Usage Statistics, Food and Environment Research Agency. http://pusstats.csl.gov.uk/ [Accessed 8 Sept

2009]

Pik, A.J., Peake, E., Strosher, M.T. and Hodgson, G.W. (1977) Fate of 3,6-Dichloropicolinic Acid in Soils J. Agric.

Food Chem., 25 (5): 1054-1061.

Recycled Organics Unit (2007a). Persistent Herbicides Risk Management Program: Research Report and

Recommended Action Plan. Second Edition. Recycled Organics Unit, internet publication:

www.recycledorganics.com

Recycled Organics Unit (2007b). Risk Assessment of Garden Maintenance Chemicals in Recycled Organics Products.

Second Edition. Recycled Organics Unit, internet publication: www.recycledorganics.com

Recycled Organics Unit (2007c). Risk Management Tools for the Recycled Organics Industry. Third Edition. Recycled

Organics Unit, internet publication: www.recycledorganics.com

Roberts-Pillon, M. (2008) DEQ Completes Three-Year Clopyralid Study. State of Oregon Department of

Environmental Quality Document DEQ-05-LQ-003

Royal Horticultural Society (2008) Contaminated manure update (6 August 2008) Published online at:

http://www.rhs.org.uk/news/Weedkiller-manure2.asp

Rynk, R. (2000) Dealing with Herbicide Residues in Compost BioCycle September: 42-47.

Rynk, R. (2001) Industries Respond to the Clopyralid Controversy. BioCycle December: 66

Rynk, R. (2002a) Prevalence and fate of clopyralid in compost BioCycle Feb 43(2): 57-60.

Rynk, R. (2002b) States take actions to protect compost against clopyralid BioCycle July 43 (7): 48-52.

Rynk, R. (2003) Oregon completes clopyralid study. BioCycle; February 44 (2): 28-30.

Smith, A.E. and Aubin, A.J. (1989) Persistence Studies with the Herbicide Clopyralid in Prairie Soils at Different

Temperatures. Bull. Environ. Contam. Toxicol. 42: 670-675.

State of Oregon Department of Environmental Quality (2003) Clopyralid Study. Accessed at

http://www.deq.state.or.us/wmc/solwaste/composting.html

Thorsness, K.B. and Messersmith, C.G. (1991) Clopyralid Influences Rotational Crops Weed Technology, 5 (1): 159-

164.

Tu, M., Hurd, C. Robison, R. & Randall, J.M (2001) Clopyralid. In The Weed Control Methods Handbook, The

Nature Conservancy.

Uhlar-Heffner, G (2001) Herbicide Manufacturers Should Accept Responsibility for Residues in Compost. BioCycle

July: 84-85.

United States Office of Prevention, Pesticides Environmental Protection and Toxic Substances Agency (7501C)

(2005) Pesticide Fact Sheet Aminopyralid

Vandervoort, C., Zabic, M.J. Branham, D. and Lickfeld, W. (1997) Fate of Selected Herbicides on Turfgrass: Effect of

Composting on Residues. Bull. Environ. Contam. Toxicol. 58: 38-45.

Waller, P. (2004) Guidelines for the specification of composted green materials used as a growing medium

component. WRAP, Banbury. ISBN: 1-84405-112-9

Washington State Department of Agriculture (2004) Ongoing Ban Works: Compost Sampling Drives Point Home.

Compost Fact Sheet.

Washington State Department of Agriculture Pesticide Management Division (2002) Clopyralid residues in compost

prompt new rules. Pesticide Notes 11 (1): 1.

Washington State University and Washington State Department of Ecology (2002) Bioassay Test for Herbicide

Residues in Compost: Protocol for Gardeners and Researchers in Washington State. Information Sheet published

online at: http://www.puyallup.wsu.edu/soilmgmt/Pubs/CloBioassay.pdf

WRAP and Environment Agency (2007) The Quality Protocol For The Production And Use Of Quality Compost From

Source-Segregated Biodegradable Waste.


http://pusstats.csl.gov.uk/

http://www.rhs.org.uk/news/Weedkiller-manure2.asp

http://www.deq.state.or.us/wmc/solwaste/composting.html

http://www.puyallup.wsu.edu/soilmgmt/Pubs/CloBioassay.pdf


systems 33

Appendix 1

Table 10 – Clopyralid-containing products sold in the UK for amateur use

Product

MAPP No

Product

Expiry Date

Marketing

Company

Crop(s) Active ingredients Maximum

application rate

Maximum

frequency

(per

year)

Evergreen

Lawn

Weedkiller

14530

31/12/2013 The Scotts

Company (UK)

Limited

lawn 5.400 g / l clopyralid

10.700 g / l fluroxypyr and

53.800 g / l MCPA

15 ml / 10 m2 1

Evergreen

Lawn

Weedkiller

Ready to Use

14531


Company (UK)

Limited

lawn 0.160 g / l clopyralid,


1.600 g / l MCPA

500 ml / 10 m2 1

Verdone Extra

13113


Company (UK)

Limited



53.800 g / l MCPA

15 ml product /10

square metres

1

Verdone Extra

Ready to use

11758


Company (UK)

Limited



1.600 g / l MCPA

500 ml product /

10 m2

1

Verdone Extra

Spot Weeder

10834


Company (UK)

Limited



1.600 g / l MCPA

500 ml product /

10 m2

1

Vitax

LawnClear 2

13508

30/04/2012 Vitax Limited lawn 27.000 g / l 2,4-D,

6.300 g / l clopyralid and

31.500 g / l MCPA

1.66 ml / m2 1

Vitax

LawnClear 2

Ready To Use

13509

31/12/2013 Vitax Limited lawn 1.130 g / l 2,4-D,

0.260 g / l clopyralid and

1.310 g / l MCPA

40 ml / m2 1 per year

Weedol Lawn

Weedkiller

14529


Company (UK)

Limited



53.800 g / l MCPA

15 ml / 10 m2 1

Weedol Lawn

Weedkiller

Ready to Use

14532


Company (UK)

Limited



1.600 g / l MCPA

500 ml / 10 m2 1 per year

https://secure.pesticides.gov.uk/pestreg/getfullproduct.asp?productid=22468&pageno=1&origin=prodsearch























systems 34

Table 11 – Clopyralid-containing products sold in the UK for professional use

Product

MAPP No

Product

Expiry Date

Marketing Company Crop(s) Active ingredients

Agrotech-Clopyralid

200 sl

12445

30/11/2009 Agrotech Trading

GmbH

barley, broccoli/calabrese, brussels

sprout, bulb onion, cabbage,

cauliflower, fodder beet, fodder rape,

forage maize, kale, linseed, mangel,

oats, oilseed rape (spring), oilseed

rape (winter), ornamental plant

production, permanent grassland, red

beet, rotational grass, salad onion,

strawberry, sugar beet, swede,

sweetcorn, turnip, wheat

clopyralid

Blaster 13267

31/12/2013 Headland Amenity Ltd amenity grassland clopyralid and triclopyr

Bofix FFC 13152

31/10/2012 Dow AgroSciences Ltd barley, oats, wheat clopyralid,florasulam and fluroxypyr

Bofix FFC 14179

31/12/2011 Dow AgroSciences Limited

barley (spring), barley (winter), oats, wheat (spring), wheat (winter)

clopyralid, florasulam and fluroxypyr

Charter 13908

31/12/2013 AgriGuard Ltd grassland clopyralid, fluroxypyr and triclopyr

Cliophar 13360

31/12/2013 Agriphar S.A barley (spring), barley (winter), maize, oats (spring), oats (winter), oilseed rape (spring), oilseed rape (winter), sugar beet, wheat (spring), wheat (winter)

clopyralid

Dow Shield 10988

31/12/2013 Dow AgroSciences Ltd barley, broccoli, brussels sprout, bulb onion, cabbage, calabrese, cauliflower, fodder beet, fodder rape, forage maize, kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter), ornamental plant production, permanent grassland, red beet, rotational grass, salad onion, strawberry, sugar beet, swede, sweetcorn, turnip, wheat

clopyralid

Esteem 12555

31/12/2013 Vitax Limited managed amenity turf 2,4-D, clopyralid and MCPA

Galaxy 13127


barley, oats, wheat clopyralid, florasulam and fluroxypyr

Galaxy 14085


barley (spring), barley (winter), oats, wheat (spring), wheat (winter)


Galera 11961


oilseed rape (winter) clopyralid and picloram














systems 35

Glopyr 200 SL 10979

31/12/2013 Globachem NV barley, broccoli/calabrese, brussels sprout, cabbage, cauliflower, fodder beet, fodder rape, forage maize, grassland (established), kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter), onion, ornamental plant production (trees)(shrubs), red beet, strawberry, sugar beet, swede, sweetcorn, turnip, wheat

clopyralid

Grazon 90 13117

31/12/2013 Dow AgroSciences Ltd grassland clopyralid and triclopyr

Greencrop Champion 11755

30/11/2009 Greencrop Technology Ltd

barley, broccoli, brussels sprout, bulb onion, cabbage, calabrese, cauliflower, fodder beet, fodder rape, forage maize, kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter), ornamental plant production, permanent grassland, red beet, rotational grass, salad onion, strawberry, sugar beet, swede, sweetcorn, turnip, wheat

clopyralid

Greenor 10909

31/12/2013 Rigby Taylor Ltd managed amenity turf clopyralid, fluroxypyr and MCPA

Interfix 14386

31/12/2013 Iticon N.V. managed amenity turf clopyralid, fluroxypyr and MCPA

Landgold Clopyralid 200 12359

30/11/2009 Teliton Ltd barley, broccoli, brussels sprout, bulb onion, cabbage, calabrese, cauliflower, fodder beet, fodder rape, forage maize, grassland, kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter), red beet, salad onion, strawberry, sugar beet, swede, sweetcorn, turnip, wheat

clopyralid

Landgold Piccant 13770

30/11/2012 Goldengrass Limited oilseed rape (winter) clopyralid and picloram

Legara 13888

30/06/2013 AgChemAccess Limited oilseed rape (winter) clopyralid and picloram

Lonpar 08686

31/12/2013 Dow AgroSciences Ltd grassland 2,4-D, clopyralid and MCPA

LONTREL 200 11558

31/12/2013 Dow AgroSciences Ltd barley, broccoli, brussels sprout, bulb onion, cabbage, calabrese, cauliflower, fodder beet, fodder rape, forage maize, kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter), ornamental plant production, permanent grassland, red beet, rotational grass, salad onion, strawberry, sugar beet, swede, sweetcorn, turnip, wheat

clopyralid

Matrikerb 10806

31/12/2013 Dow AgroSciences Ltd (Contact PSD for approved crop/use information)

clopyralid and propyzamide















systems 36

Milentus Clopyralid 12448

30/11/2009 Milentus BV barley, broccoli/calabrese, brussels sprout, bulb onion, cabbage, cauliflower, fodder beet, fodder rape, forage maize, kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter) more

clopyralid

Nugget 13121

31/12/2013 AgriGuard Ltd oilseed rape (winter) clopyralid and picloram

Pastor 11168

31/12/2013 Dow AgroSciences Ltd permanent grassland, rotational grass clopyralid, fluroxypyr and triclopyr

Piccant 14294


Pirlid 11946

30/11/2009 Tronsan Ltd barley, broccoli/calabrese, brussels sprout, bulb onion, cabbage, cauliflower, fodder beet, fodder rape, forage maize, kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter), ornamental plant production, permanent grassland, red beet, rotational grass, salad onion, strawberry, sugar beet, swede, sweetcorn, turnip, wheat

clopyralid

Praxys 13912


amenity grassland, lawn, managed amenity turf


Prevail 13205



Renegade 14507

31/12/2013 Chemsource Ltd oilseed rape (winter) clopyralid and picloram

Spearhead 09941

31/12/2013 Bayer Environmental Science

amenity turf (managed) clopyralid, diflufenican and MCPA

Thistlex 11533

31/12/2013 Dow AgroSciences Ltd permanent grassland, rotational grass clopyralid and triclopyr

Torate 12611

30/11/2009 AgriGuard Ltd barley, broccoli, brussels sprout, bulb onion, cabbage, calabrese, cauliflower, fodder beet, fodder rape, forage maize, grassland, kale, linseed, mangel, oats, oilseed rape (spring), oilseed rape (winter), ornamental plant production, red beet, strawberry, sugar beet, swede, sweetcorn, turnip, wheat

clopyralid

Trinity 12738

28/02/2012 AgriGuard Ltd grassland clopyralid, fluroxypyr and triclopyr

Vivendi 200 12782

31/12/2013 Agrichem BV barley, broccoli/calabrese, brussels sprout, bulb onion, cabbage, fodder beet, fodder rape, forage maize, kale, linseed, mangel, oats, oilseed rape, ornamental plant production, permanent grassland, red beet, salad onion, strawberry (outdoor use only), sugar beet, swede, sweetcorn, turnip, wheat

clopyralid


https://secure.pesticides.gov.uk/pestreg/getcropdetails.asp?productid=19128&pageno=3&origin=prodsearch














systems 37

Table 12 - Aminopyralid-containing products approved for use in November 2009

Product

MAPP No

Product

Expiry Date


Forefront

14701

29/07/2011 Dow AgroSciences

Limited

grassland aminopyralid and

fluroxypyr

Halcyon

12749


Limited

permanent grassland, rotational grass aminopyralid and

fluroxypyr

Halcyon

14709


Limited


fluroxypyr

Mileway

14702


Limited

amenity grassland aminopyralid and

fluroxypyr

Pharaoh

13631


Limited


triclopyr

Pharaoh

14731


Limited


triclopyr

Pro-Banish

14730


Limited

grassland aminopyralid

Synero

14059


Limited


fluroxypyr

Synero

14708


Limited


fluroxypyr

Table 13 - Aminopyralid-containing products approved for use before July 2008

Approved for amateur use

Product MAPP

No Marketing Company Crop(s) Active(s)

Banish5

Dow AgroSciences Ltd grassland 30 g / l Aminopyralid

13766

Approved for professional use

Forefront Dow AgroSciences Ltd

permanent grassland,

rotational grass 30 g / l Aminopyralid and 100 g / l fluroxypyr

12765

Halcyon Dow AgroSciences Ltd



12749

Pharaoh Dow AgroSciences Ltd grassland 30 g / l Aminopyralid and 240 g / l triclopyr

13631

Pro-Banish Dow AgroSciences Ltd


rotational grass 30 g / l Aminopyralid

13767

Runway Dow AgroSciences Ltd amenity grassland 30 g / l Aminopyralid and 100 g / l fluroxypyr

14017

5 This was never marketed in the UK (Source DowAgroSciences)











systems 38

Synero Dow AgroSciences Ltd amenity grassland 30 g / l Aminopyralid and 100 g / l fluroxypyr

14059

Upfront

AgChemAccess Ltd permanent grassland,


13782


systems 39

Table 14 - Picloram containing products registered in the UK

Product

MAPP No

Product

Expiry Date


Atladox HI 05559

31/12/2010 Nomix Enviro Limited land not intended for cropping 2,4-D and picloram

Atladox Hi 13867

31/03/2013 Nomix Enviro, A Division of Frontier Agriculture Limited

land not intended for cropping 2,4-D and picloram

Galera 11961



Landgold Piccant 13770


Legara 13888

30/06/2013 AgChemAccess Limited oilseed rape (winter) clopyralid and picloram

Nugget 13121

31/12/2013 AgriGuard Ltd oilseed rape (winter) clopyralid and picloram

Pantheon 13695

31/12/2010 Pan Agriculture Limited

land not intended for cropping picloram

Pantheon 2 14052

31/12/2013 Pan Agriculture Limited


Piccant 14294


Prevail 13205



Renegade 14507

31/12/2013 Chemsource Ltd oilseed rape (winter) clopyralid and picloram

RouteOne Loram 24 13951

31/12/2013 Albaugh UK Limited land not intended for cropping picloram

Tordon 101 05816


land not intended for cropping 2,4-D and picloram

Tordon 22K 05083



Tordon 22K 05790

31/12/2010 Nomix Enviro Limited land not intended for cropping picloram

Tordon 22K 13869

31/03/2013 Nomix Enviro, A Division of Frontier Agriculture Limited



















systems 40

Appendix 2

Literature review of garden waste composition

12.0 Introduction A short literature review was conducted to assess the composition of garden waste collected separately for

composting across the UK. The search was carried out on-line using a number of search engines and databases,

including Google Scholar, www.ojose.com, High Wire Press, and www.researchgate.net, in addition to the

author‘s own library. The search included studies assessing the composition of municipal waste in general, home

composting studies, WRAP‘s own research into separate organics collections and the variability of compost

quality.

12.1 Results from England The literature review indicated a paucity of data on the composition of green waste and how this varied

throughout the year. Most compositional studies sorted municipal waste into various categories, however,

‗garden waste‘ was nearly always classified into a single category. The data obtained are summarised below.

12.1.1 Morpeth, Northumberland The most comprehensive data set identified in this literature search was obtained by the Open University / HDRA

during research on behalf of the Environment Agency (HDRA & Open University, 1999). The trial assessed a

garden and food waste6 co-collection from 4,000 households in Castle Morpeth during 1995/96, where the waste

was collected fortnightly in a 240 litre wheeled bin. Households involved in the trial had, in general, large

gardens. Waste was sorted using the ‗cone and quarter‘ technique, and classified into six categories, namely:

grass cuttings, dried leaves, green leafy, woody brown, putrescibles and contaminants. The data are shown in

Table 15 and Figure 3.

Collectively they suggest that grass clippings comprised over 60% by mass of the total waste collected between

May and September, and illustrate the considerable seasonal variation in green waste composition throughout

the year. Not surprisingly, hardly any grass was collected during November and December.

Table 15– Summary of green waste composition in the Morpeth trial

(% Fresh weight ± SE)

June 1995

September 1995 December 1995 April 1996

Grass cuttings

84.4 ± 12.3

65.2 ± 4.5 1.2 ± 0.1 35.0 ± 5.0

Dried leaves

1.1 ± 1.1

0.5 ± 0 92.3 ± 3.8 33.4 ± 3.5

Green (leafy)

1.2 ± 0.9

15.5 ± 11.1 0.5 ± 1.0 6.3 ± 1.3

Brown (woody)

3.8 ± 2.7

15.5 ± 5.0 4.5 ± 0.1 22.0 ± 2.0

Putrescibles

1.8 ± 1.4

0.5 ± 1.0 0.7 ± 0.3 4.0 ± 1.0

Contaminants

7.7 ± 10.1

2.8 ± 0.5 0.8 ± 0.3 0.35 ± 0.15

Source: Environment Agency Technical Report P314; reproduced with permission

6 This scheme pre-dated the introduction of the Animal By-Products Regulation

http://www.ojose.com/

http://www.researchgate.net/


systems 41

Figure 3 – Seasonal variation in proportion of grass clippings collected in green / food

waste co-collection at Castle Morpeth in 1995/96

Source: Ibid; reproduced with permission

12.1.2 Dogsthorpe, Peterborough The composition of green waste collected at the Dogsthorpe open windrow composting facility during 1995 / 96

was also determined as part of the above composting research programme funded by the Environment Agency

(AEA Technology, 2000). Researchers at AEA Technology categorised green waste collected at the city‘s

household waste recycling centres; samples were sorted into 13 categories on both bulk samples (i.e. pre-

shredding), or post-shredded material. The data, shown in Table 16, suggest that negligible quantities of grass

clippings were identified. Even though 1995 was a hot, dry summer, it is surprising the analyses didn‘t identify

grass during the autumn period. Rather, as the sampling methodology differed from that used in the Morpeth

trial, it is possible that grass was classified into the ‗fines‘ category, which averaged 29% (m/m) during the year

of the shredded samples. This illustrates the importance of using an appropriate sampling technique.

12.1.3 Nine English local authorities As part of a wider study funded by WRAP looking into home composting, garden waste from nine English local

authority areas was sampled during June and September 2004. (A variety of garden waste collection methods

were used across the sample authorities). During June, garden waste comprised approximately 21% (by mass),

whereas during September it fell to about 12%.

May Jul Aug Sept Nov Dec March Jun

An investigation of clopyralid and aminopyralid in commercial composting systems 42

Table 16– Summary of green waste composition at Dogsthorpe

Bulk Samples of

Feedstock received

(prior to shredding)

(% mass/ mass)

Shredded feedstocks (< 50 mm)

(% mass/ mass)

Delivery date August

1995

Jan 1996 August

1995

Sept 1995 Oct 1995 Nov 1995 Dec 1995 Jan 1996 Feb 1996 March

1996

Category

Grass Cuttings 1.05 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Green Foliage 19.4 20.66 2.80 2.81 42.31 1.13 1.4 51.46 41.8 36.46

Soft Prunings 7.73 0.08 11.2 11.2 0.00 0.00 0.00 0.00 0.00 2.00

Logs/Tree Trunks 7.49 27.79 5.6 5.6 4.83 3.87 3.77 12.05 13.3 12.8

Autumn Leaves 2.01 0.23 2.02 2.02 0.57 7.97 7.49 095 2.71 3.52

Soil 3.14 2.64 2.74 2.75 0 17.23 15.23 3.25 10.45 5.24

Allotment Waste 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 3.84

Fruit 2.01 0.04 0.00 0.00 0.04 0.00 0.00 0.00 0.00 0.9

Hard Prunings 9.47 14.65 14.79 14.78 7.6 24.87 23.14 18.23 19.14 18.16

Putrescibles 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Fines 22.8 30.78 46.47 46.47 43.98 28.73 32.79 14.04 12.6 10.2

Other readily degradables ND ND 13.26 13.26 0.00 14.69 14.55 0.00 0.00 0.00

Contaminants 24.9 3.15 1.12 1.11 0.67 1.52 1.63 0.00 0.00 6.89

Reproduced with permission.


systems 43

12.2 European data Given the lack of UK-based data, the literature search was expanded to include data published in peer reviewed

journals from within Europe.

12.2.1 Hamburg, Germany The most comprehensive study was reported by Krogmann (1999), who investigated the effects of season and

housing type on the composition of separately collected biowastes (garden and food wastes) from households in

Hamburg, Germany. The % grass (by mass) based on three housing types are shown in Figure 4. The data

presented were derived from Krogmann‘s and based on the % of the garden waste fraction only.

Figure 4 – Variation in grass collected in a garden / food waste collection scheme in

Hamburg, Germany

These data show that greatest proportion of grass clippings were collected during the spring and summer

months, with the single family and town houses presenting the greatest amount during the spring time. Notably,

in the downtown area, the greatest proportion of grass was obtained during summer, although these houses

were less likely to have large gardens.

12.2.2 Aarhus, Denmark Researchers in Denmark sampled garden waste eight times over a period of a year (twice in every season),

sorting into five different fractions (Boldrin & Christensen, 2010). Unfortunately grass clippings were classified in

the ―small stuff‖ category, which included grass, flowers, soil etc. This fraction was shown to comprise just over

50% (by mass) in January, rising to above 90% in September, with an annual weighted average of just over

75%.

12.3 Conclusions The results from this literature review indicate there is a paucity of data on the composition of garden waste

collected for biological treatment, with research at Morpeth, Northumberland, providing the most comprehensive

datasets. In general, the proportion of grass clippings was greatest during the spring months, although data

from Germany appeared to suggest this was influenced by housing type. In Morpeth, over 60% of the total

garden waste collected in wheeled bins was grass during May to September.

In order to gain a better understanding of the potential risks associated with contaminants (e.g. clopyralid) that

may enter a commercial composting system through garden wastes, a better understanding of garden waste

composition and variation would be beneficial. This would need to accommodate differing collection systems

(bring and kerbside), housing types and local policies for residual waste collection.

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an investigation of clopyralid and aminopyralid in commercial composting systems

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