Weed research for cereals and oilseeds

An over-reliance on a limited group of herbicide modes of action has accelerated the development of resistant weeds. AHDB research helps to identify resistance risks and improve management guidance for the control of grass weeds and broad-leaved weeds.

Loss of key herbicide active ingredients in cereals and oilseed rape due to changes in legislation has been compounded by resistance to many of the remaining herbicides. A dominance of autumn-sown arable crops and herbicide resistance mean black-grass has become a major headache for many farmers. However, populations of wild-oats, ryegrass, poppy, chickweed and mayweed have all been found to be resistant to some herbicides in some locations. Resistance issues are also emerging in bromes. Controlling herbicide-resistant weed populations incurs additional costs.

AHDB research focuses on:

• Monitoring herbicide resistance presence and distribution
• Exploring integrated pest management (IPM) options for control
• Communicating weed management guidance

Weed Resistance Action Group (WRAG)

AHDB works with WRAG to develop, produce, and promote guidance on herbicide resistance.

AHDB PhD student Jed Clark is exploring what gives some crops and varieties the power to fight back against black-grass. In this battlefield, roots are in charge – something that is difficult to assess in commercial field crops. Jed has devised an experimental system that allows him to use containers to pit crop against weed. The approach also allows the environment to be controlled and, via the use of permeable and non-permeable barriers in the containers, permits the assessment of physical and chemical interactions. Ultimately, the project will allow for enhanced competitiveness to be selected through plant breeding.

*A report is submitted at the end of each project. After review (which can take several weeks), the final project report is published on the corresponding project page. At this stage, the project is official complete.

Brome management

Your field’s seedbank provides a unique evidence trail that, following a forensic analysis, can help shape management decisions. Central to any detective work is the assessment of the weed species present and, increasingly, their herbicide-resistance status. As this isn’t easy, we commissioned ADAS to conduct an evidence-based assessment of UK brome populations. A UK-wide survey found that accurate identification of brome was generally poor. This is problematic because the best management approach depends on the species present – and with herbicide resistance concerns thrown into the mix, knowing which brome is in your field is going to become more important.

Glyphosate guidelines

In 2021, the Weed Resistance Action Group (WRAG) glyphosate guidance was updated. It included a revision to dose to ensure that there are ‘no survivors’ following an application. Survivors help drive the evolution of herbicide resistance. Typically, annual grasses require a minimum of 540 g a.i./ha for seedlings up to 2–3 leaves, 720 g a.i./ha when tillering and 1,080 g a.i./ha when flowering. The specific tillering dose is new. Robust rates are needed to ensure complete kill. The revised guidance was based on the results from a five-year investment in research by AHDB.

Other recently completed projects

Information on all pest research projects is available in our research archive:

• In the ‘Sector’ drop-down box, select ‘Cereals & Oilseeds’
• In the ‘Topic’ drop-down box, select ‘Weed management’