The Weed Resistance Action Group (WRAG)

The Weed Resistance Action Group (WRAG) produces guidance on pesticide resistance issues. Hosted by AHDB, this information can be used to help protect crops and the long-term efficacy of herbicides.

The AHDB-supported Resistance Action Groups (RAGs) are informal, UK-based groups consisting of experts from the Crop Protection Association (CPA) member companies, other representatives from the agrochemical industry, a range of independent organisations, including public-sector research institutes, and the Chemicals Regulation Directorate (CRD).

About the Weed Resistance Action Group (WRAG)

Insecticide Resistance Action Group (IRAG)

Fungicide Resistance Action Group (FRAG)


Reports: Glyphosate

Reports: Black-grass (mainly)

Reports: Other grasses

Reports: Broad-leaved weeds

In this video (above), AHDB's Paul Gosling describes the findings from AHDB research that investigates how farming practices can alter the risk of glyphosate resistance developing in UK grassweeds.

Herbicide Mode of Action Classification

To find a herbicide's mode of action group, use the Herbicide Resistance Action Committee (HRAC) Mode of Action Classification Map.

HRAC Mode of Action Classification 2022 Map

From 2020, the classification system aligns with the system used by the Weed Science Society of America (WSSA).

This list shows the current groups (with pre-2020 legacy HRAC codes in brackets).

  • 1 (A) Inhibition of ACCase
  • 2 (B) Inhibition of ALS
  • 3 (K1) Inhibition of microtubule assembly
  • 4 (O) Auxin mimics
  • 5 (C1,2) Inhibition of photosynthesis: PS ll – Serine 264
  • 6 (C3)Inhibition of photosynthesis: PS ll – Histidine 215
  • 9 (G) Inhibition of EPSP synthase
  • 10 (H) Inhibition of glutamine synthetase
  • 12 (F1) Inhibition of PDS
  • 13 (F4) Inhibition of DOXP synthase
  • 14 (E) Inhibition of PPO
  • 15 (K3) Inhibition of VLCFAs
  • 18 (I) DHP inhibition
  • 19 (P) Auxin transport inhibitors
  • 22 (D) PS l electron diversion
  • 23 (K2) Inhibition of microtubule organization
  • 24 (M) Uncouplers
  • 27 (F2) Inhibition of HPPD
  • 29 (L) Inhibition of cellulose synthesis
  • 30 (Q) Inhibition of fatty acid thioesterase
  • 31 (R) Inhibition of serine threonine protein phosphatase
  • 32 (S) Inhibition of solanesyl diphosphate synthase
  • 33 (T) Inhibition of homogentisate solanesyltransferase
  • 34 (F3) Inhibition of lycopene cyclase
  • 0 (Z) Unknown mode of action

Mode of action labelling for UK plant protection products

From 2023, all UK plant protection products will include mode of action (MoA) information on their labels.

The decision – by the Health and Safety Executive (HSE) – follows a joint statement issued by the UK Resistance Action Groups (UK-RAGs) in December 2017. This said that greater prominence of MoA information would help farmers and agronomists make informed resistance management decisions.

Since then, members of the industry body ‘CropLife International’ have made a voluntarily commitment to include MoA icons and groups on all product labels by 2023. Following consultation with the Crop Protection Association (CPA), the HSE announced that it will become a legal requirement to include MoA information on all UK product labels from January 2023.