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Rothamsted Research have produced two new publications concerning black-grass, resistance and control. (July 2013)

Black-grass (Alopecurus myosuroides): Everything you really wanted to know about black-grass but didn't know who to ask. (pdf, 4 pages, 2013)

Black-grass: The potential of non-chemical control. (pdf, 4 pages, June 2013)

The WRAG Steering Group has produced a leaflet on 'The Benefits of Herbicide Resistance Testing'. This provides important advice on identifying when a test might be appropriate and also advice on ensuring that sample collection, testing and interpretation are done correctly. (June 2012)(pdf, 4 pages, 3 Mb)

HGCA Managing weeds in arable rotations - a guide (Summer 2010) (pdf, 24 pages, 2.5 Mb)

At 'Cereals 2010' the HGCA launched the publication "Managing weeds in arable rotations". This incorporates the latest version of the WRAG Guidelines and updates the 2003 version. Most importantly, this puts herbicide resistance into the context of managing weeds across the rotation and includes advice not only on chemical options for weed control, but emphasises the need to use all the tools in the weed management toolbox.

WRAG response on Trifluralin (3 pages pdf)

At its May (2007) meeting the Weed Resistance Action Group (WRAG) steering committee discussed the implications of the loss of trifluralin, which has not been included in Annex 1 of Directive 91/414 and will be withdrawn by the middle of 2009. The committee decided to write to Martin Ward, the new policy director at PSD, to make him aware of our concerns.

Ten facts everyone should know about herbicide resistance

The Steering Group of (WRAG) has produced a list of 10 facts that everyone should know about herbicide resistance in grass-weeds (black-grass, Italian rye-grass, wild oats). Whilst they are often over simplifications, this basic level of knowledge is essential in order to develop an effective strategy to manage resistant grass weeds.

Ten facts everyone should know about herbicide resistance.

Herbicide-resistant black-grass: managing risk with few options

Home-Grown Cereals Authority (HGCA) has recently published an Information Sheet 03 entitled 'Herbicide-resistant black-grass: managing risk with few options'.

Introduction

WRAG was formed in 1989 as an informal group of representatives of the British Agrochemicals Association's (BAA) (now the Crop Protection Association (CPA)) member companies and other organisations involved in herbicide resistance research. These other organisations include Rothamsted Research, ADAS Limited (ADAS), Health and Safety Executive's Chemicals Regulation Directorate (CRD) (then Defra's PSD), Universities, Colleges, and the (HGCA).

The Objectives of Weed Resistance Action Group (WRAG) are:

  • to provide a forum for information exchange between people actively involved in research into herbicide resistance;
  • to discuss strategies to avoid resistance and to manage resistant populations;
  • to define research needs;
  • to discuss test methodology and agree standards;
  • to agree statements for the media, whether in response to queries or as unsolicited news releases;
  • to maintain communication with similar groups which have been established successfully in other countries.

WRAG is independent but maintains good liaison with the Herbicides Resistance Action Committee (HRAC), which has representation only from the agrochemical industry. WRAG has similar aims and objectives to HRAC, but considers that there is an advantage in having a platform for both independent and commercial interests. A steering group of representatives meets 2-3 times per year, and relevant information is conveyed to all members. Occasional open meetings are also arranged.

The steering group currently comprises:

James Clarke (Chairman), ADAS Boxworth

Stephen Moss (Secretary), Rothamsted Research

Ingrid den Hoed CRD, HSE

Mark Ballingall, Scottish Agricultural Colleges (SAC)

Gordon Anderson-Taylor, Bayer CropScience Ltd

Steve Cranwell, DuPont UK Ltd

Jason Tatnell, Syngenta Crop Protection UK Ltd

Clare Bend, Masstock

Herbicide-resistant weeds present in the UK:

Alopecurus myosuroides (black-grass)

Results of a random survey in 2002 indicate that resistant black-grass occurs on virtually every farm in England where herbicides are used regularly for its control. Enhanced metabolism is the commonest mechanism of resistance, resulting in partial resistance to a wide range of active ingredients. Target site acetyl-CoA carboxylase (ACCase) resistance, which gives absolute resistance to 'fop' and 'dim' herbicides, is increasing. There is increasing concern about resistance to Acetolactate synthase (ALS) inhibiting herbicides (for example sulfonylureas) which are being used increasingly for grass-weed control.

Avena spp. (wild-oats)

Resistant populations of both Avena fatua and Avena sterilis ssp. ludoviciana occur widely, although the number of farms affect is far less than for black-grass. Resistance is often confined to discrete patches. The recent withdrawal of several wild-oat herbicides (for example tri-allate, difenzoquat, flamprop-M-isoppropyl) from the UK market is resulting in increased dependence on ACCase and ALS inhibiting herbicides. This may increase the risk of resistance in the future.

Lolium multiflorum (Italian rye-grass)

Resistance to diclofop and tralkoxydim is an increasing problem on arable farms in some counties of England. Most of the affected farms have not sown rye-grass for many years. This weed is highly competitive and difficult to control at high populations.

Stellaria media (common chickweed) and Papaver rhoeas (common poppy)

Resistance to sulfonylurea herbicides occurs in a few counties of England and Scotland, especially where there has been heavy reliance on these herbicides. Populations resistant to synthetic auxins have also been identified.

The following species of triazine-resistant weeds have been found in the UK, usually in horticultural or non-crop situations: Chenopodium album (fat hen), Conyza canadensis (Canadian fleabane), Epilobium ciliatum (American willowherb), Matricaria discoidea (pineapple weed), Poa annua (annual meadow-grass), Senecio vulgaris (groundsel), Solanum nigrum (black nightshade). A few populations of paraquat-resistant Poa annua and Epilobium ciliatum have also been recorded.

Guidelines

In 2003, WRAG produced a revised version of the Guidelines: "Managing and Preventing Herbicide Resistance in Weeds" (pdf, 12 pages, 1Mb). This replaces the 1997 version, has an improved layout, includes new knowledge, gives specific advice for each grass-weed and includes broad-leaved weeds for the first time. This 12 page leaflet was published with financial support from the (HGCA).

These guidelines have now been updated by the HGCA publication "Managing weeds in arable rotations - a guide (Summer 2010)" which incorporates the latest version of the WRAG Guidelines and was launched at 'Cereals 2010'. The new guide puts herbicide resistance into the context of managing weeds across the rotation and includes advice not only on chemical options for weed control but emphasises the need to use all the tools in the weed management toolbox.

Grass-weed herbicides - mode of action table

A list of herbicide groups and examples of grass weed products is available.

Broad-leaved weed resistance - review (part PS2709)

PSD funded a project (PS2709) in 2006-2008, investigating broad-leaved weed resistance. As part of this project the current status of herbicide-resistance in broad-leaved weeds world-wide was reviewed and summarised by ADAS and Rothamsted Research in order to help predict which species are likely to evolve resistance in the UK. Herbicide resistance continues to challenge agriculture and horticulture, and is a potential threat to the industrial and amenity sectors. This review uniquely investigates the problem of herbicide resistance from the chemical and biological point of view. A copy of the review and a leaflet, targeted at the amenity weed control sector, are available.

Broad-leaved weed resistance review (pdf, 52 pages)

Herbicide Resistance in Amenity Weed Control Situations leaflet (pdf, 2 pages)

Technical Fact sheet

In July 2004, PSD and Defra funded a fact sheet looking at herbicide resistant grassweeds, which was produced and circulated in Crops magazine. This fact sheet, which was written by Rothamsted Research and ADAS, lists key risk factors that influence the development of grassweed resistance. The second part of the fact sheet is an audit that can be used to assess the risk of current practices and how changing these will reduce the risk of herbicide resistance development. Both the fact sheet and a spreadsheet version of the audit form are available.

Herbicide Resistant Grassweeds - Are you at risk? A technical fact sheet (pdf)

Audit Spreadsheet (excel)

September 2005 Special Meeting

On 23rd September 2005, PSD (now CRD) hosted a special meeting of WRAG to discuss resistance risk assessment for use of herbicides with grass-weed activity in sequence or mixture. Attendees at this meeting included all members of the steering committee and representatives from across the industry.

PSD produced a paper which the meeting used to focus discussion, together with a series of presentations. The meeting also discussed the Herbicide Resistance Management: Evaluation of Strategies) (HeRMES) research project which had recently reported.

The original discussion papers, presentations and agreed minutes are linked below:

Following this meeting PSD produced a paper for consideration by the Advisory Committee on Pesticides (ACP). The ACP considered this paper at their November meeting and this paper will be added to this site shortly.

ACP paper on Herbicide Resistance

As a result of the 23rd September 2005 special WRAG meeting PSD (now CRD) wrote a paper on herbicide resistance for the November ACP. The link below is the paper prepared for disclosure.

PSD will now be working to produce a detailed implementation plan and the industry will have an opportunity to comment on this. This implementation plan will include consideration of the economic implications and an education programme.

Ten facts everyone should know about herbicide resistance

The Steering Group of Weed Resistance Action Group (WRAG) has produced a list of 10 facts that everyone should know about herbicide resistance in grass-weeds (black-grass, Italian rye-grass, wild oats). Whilst they are often over simplifications, this basic level of knowledge is essential in order to develop an effective strategy to manage resistant grass weeds.

Ten facts everyone should know about herbicide resistance.

Further WRAG Information

For more information regarding WRAG, please contact the secretary.

Dr Stephen Moss (WRAG Secretary)
Rothamsted Research
Harpenden, Herts. AL5 2JQ, UK
Tel: 01582-763133 ext. 2521
Fax: 01582-760981
E-mail: stephen.moss@rothamsted.ac.uk

Minutes of meetings

Steering group meeting 27th November 2013

Steering group meeting 15th March 2012

Steering group meeting 17th March 2011

Steering group meeting 18th March 2010

Steering group meeting 3rd December 2009

Steering group meeting 16 April 2008

Steering group meeting 12 December 2007

Steering group meeting 8 May 2007

WRAG letter to PSD (May 2007) regarding trifluralin

Steering group meeting 24 November 2006

Steering group meeting 17 May 2006

Steering group meeting 14 November 2005

Steering group meeting 6 April 2005

Steering group meeting 8 October 2004

Steering group meeting 11th September 2003

Steering group meeting 13th November 2002

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