Mode of Action Classification

As weeds are the top yield robbers in global agricultural cropping systems herbicides are pivotal to control weeds and to secure yield allowing a sustainable agricultural practice.

The HRAC Mode of Action Working Group aims to provide an overview of herbicides based on targets and modes of action. We strive to provide the practitioners in agriculture as well as researchers in academia, institutions and organizations as well as other interested parties with information on herbicide active ingredients to allow sustainable use of the actives.

In summary, we aim to contribute to integrated weed management to avoid herbicide resistance buildup by showcasing the different modes of action.

The working group discusses and implements changes of the HRAC Mode of Action Classification poster. We strive to include latest scientific knowledge on actives and their targets for the mode of action classification to add actives to the poster or to take off certain actives from the poster. We evaluate requests by companies to add new chemistries to the poster in alignment with WSSA representatives.

The working group defines further content on the poster, and we decide on the layout of the classification overview in cooperation with a graphics service provider. We aim at a biannual release of updates of the HRAC Mode of Action Classification poster to reflect latest knowledge gain.

In 2025 the HRAC Mode of Action Working Group included changes proposed by Working Group 3 and 23 on microtubule related actives and implemented changes to be showcased in the HRAC Mode of Action Classification 2026.

Moreover, the working group members analyzed sales data of actives across three database sources to identify outdated or irrelevant active ingredients, and we judged on the final decision including also the input of regional HRAC chairs. Actives without sales or with very low sales below 2 million € global sales and no importance for herbicide resistance management or with global sales below 0.5 million € global sales with marginal herbicide resistance management importance were decided to be taken off the poster. All past and present herbicides on the poster are kept in a herbicide master sheet list available at the HRAC website.

The working group publishes reports on the deliverables of the working group as well as changes on the latest version of the HRAC Mode of Action Classification poster.

We take part in international congresses, and we liaise with stakeholders around herbicides.

We prepared a report summarizing about main activities during 2024 and 2025 and the respective outcomes. Please access the information here.