Front cover of Guide

AHDB Guide from 2021 incorporating WRAG guidelines.

Weed control is vital for high yields of good-quality crops and to prevent the spread of pests and diseases, e.g. ergot. Yet with fewer active ingredients, a need to protect water and manage herbicide resistance, the weed challenge must be managed across the rotation.

Weed control is more than just using herbicides. Many factors determine weed incidence and effective weed management in arable crops requires integration of all these factors:

  • Crop choice and rotation
  • Managing the weed seedbank
  • Cultivations
  • Drilling date
  • Crop competition
  • Herbicide choice, application and timing
  • Recent weed-control strategies
  • Weather
  • Agronomist/farmer perceptions

The aim of this publication is to provide a practical guide for farmers and agronomists that brings together research to allow improved weed management through a rotation dominated by autumn-sown crops.

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A weed can have many definitions, one being, any plant growing in a place it is not wanted. This topic focuses mainly on weeds affecting agriculture. Generally weeds are classified into two groups: grass-weeds (e.g Black-grass, Italian ryegrass, Bromes) and broad-leaved weeds (e.g Mayweed, Chickweed, Poppy, Cleavers). 

The major commodity crops in the UK are wheat, barley, oilseed rape, field beans, sugar beet and potatoes, but around half of agricultural land grows grass.   

Rothamsted Research is a world-leading, non-profit research centre that focuses on strategic agricultural science to the benefit of farmers and society worldwide.

Integrated farming is a type of farming that aims to maximize the efficiency and productivity of the farm by integrating different types of crops and animals into a single system.

The Voluntary Initiative is an industry led programme to promote the responsible use of plant protection products (PPP's) through schemes, tools and messages advocating an IPM-based approach to sustainable agriculture.

Herbicide resistance is the inherited ability of a weed to survive a rate of herbicide which would be lethal to a member of the normal population. It can develop over time based on repeated selection pressure imposed on the weed. This selection pressure changes the population from susceptible to resistant. Herbicide resistance is becoming an increasing problem in UK agriculture, in both grass weeds and broad-leaf weeds. See also the general topic on herbicides.

Arable crops in the UK make up just under half of the farmed area (3.9M ha out of 9M ha)

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.

Innovative Farmers are launching a new field lab exploring the use of poly cropping, inoculants and undersown cover crops to control blackgrass (BG) in spring and winter-sown crops.  

Wild-oats are a highly competitive grass-weed in the UK of which there are two important species: common wild-oats (Avena fatua) and winter wild-oats (Avena sterilis ssp. ludoviciana). Failure to control wild oats in arable fields can lead to high penalties to yield, seed crop contamination, income loss for farmers and reduced competitiveness of UK agriculture. Whilst herbicide resistance selection has been slower in wild-oats compared to other grass weeds such as Black-grass (Alopecurus myosuroides), it is still a growing problem and since this report was published in 2001, resistance has been reported across hundreds of farms across many UK counties.  Continuing development of herbicide resistance in wild-oats will limit pesticide choice and possibly lead to a higher dependence on environmentally 'risky' herbicides that are more likely to reach water. The objective of this project was to conduct and collate research on the characterisation of herbicide resistance in wild-oats with the aim of informing strategies for the prevention, containment and control of herbicide resistant populations. Links to the full project are provided at the bottom of the page.