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Weed control options and future opportunities for UK crops (research review)

Research Review No. CP 182 / 1807258

Weed control options and future opportunities for UK crops

Authors: Sarah K. Cook, Laura R. Davies, Frances Pickering, Lynn V. Tatnell, Angela Huckle, Sonia Newman, Chloe Whiteside, Charlotte White, David Talbot, Helen Holmes (ADAS), Patricia E. Turnbull (Independent agronomist), Denis C. Buckley (Independent agronomist), Jim Scrimshaw (PGRO) and Pamela Chambers (UPL)

Editors: James H Clarke, Steve Ellis and Sarah Clarke (ADAS Boxworth, Boxworth, Cambs CB23 4NN)

Overall recommendations and priorities

Increase access to and use of current knowledge

Many growers are probably unaware of all the weed management information that is available to them. Knowledge is also often kept within the individual sectors.There is much relevant work on weeds that was once funded by MAFF or Defra and it is often hard to find, with only the current researchers knowing of its existence and so it will be lost when they leave the industry. Peer-reviewed information is also unavailable to many potential beneficiaries. Consequently, making better use of existing knowledge is a very high priority. Enabling greater access to it should be a high priority. Eroding barriers between different cropping sectors, through putting the weed biology at the centre of the knowledge, will enable good progress in all sectors.  Decision support tools that incorporate up-to-date information on weed management could also be developed. A targeted, central location for weed control, which covers all crop sectors, should also be developed.

Link practical knowledge better with fundamental research

As in many other science disciplines, there is too great a gap between those who undertake fundamental research and those who look to apply their findings in practice.  There is huge scope to derive more benefits from research. To do so needs more involvement of those with an in-depth and practical understanding of weed management in the setting of project objectives. A good example would be to better focus research on those areas where gaps in the understanding of weed biology are hindering the development of better control options.

Maximise herbicide availability

The availability of herbicides continues to decline. Further actives will be withdrawn and there are unlikely to be many new herbicides to replace them. Good stewardship of current active substances is vital and requires companies, regulators and users to work together to retain them, through continued support and prevention of bad practice.

Retaining product efficacy, by minimising resistance and ensuring good practice, is something over which agronomists and growers have considerable ‘control’. Much is known about the risks of weeds developing resistance to herbicides. Pro-active identification of the high-risk uses/situations, which could select for resistance, should be a priority. Weed management strategies for these high-risk situations should be agreed and communicated widely. Monitoring of weed species shifts and emerging cases of herbicide resistance, in relation to herbicide use and other integrated weed management strategies, is needed.

Agree funding for Integrated Weed Management (IWM)

Both growers and politicians recognise the need to maximise non-chemical control of weeds and develop integrated weed management. However, research in these areas, typically, does not attract commercial funding. To ensure future development of sustainable weed management solutions, collective funding from farmers/growers and/or those promoting non-chemical approaches is required. The availability of suitable funding mechanisms, to drive what are often too costly and less effective options, is not an industry priority. However, if government and industry can work together it will be possible to make more progress than is currently the case. 

Weed research and approaches to control need to be considered more strategically

Reviewing and compiling information for this review has highlighted how the current approach to weed control is very often based on the use of herbicides against specific weeds and/or in specific crops. It is very clear, however, that, as with nutrient and soil management, there is considerable scope for a more strategic approach that is relevant to the whole cropping system, which can then be deployed in specific crops. A key recommendation is that there should be a more strategic approach to weed research and control.

Putting weed biology/weed life cycles at the heart of control strategies will enable more rapid progress across multiple crops. Interventions need to target and exploit the weakest stage of the weed life cycle, while maximising the tolerance of the current and future crops. A cross-sector, multi-annual approach is therefore vital.

Understand selectivity between crops and weeds

All technologies require a differential selectivity between the crop and the weed. Development of appropriate techniques will build on those principles. Selectivity can be achieved by a number of routes:

Spatial selectivity is a major opportunity for chemical and non-chemical approaches and irrespective of the crop we need to be able to identify one from the other. The wider the row spacing, the greater the opportunities. This could be optical and ground or satellite based. Additionally, alternative ways of highlighting where the crop is (‘plant marking’) should be considered, such as by seed treatments or genetic. There are now much better systems to detect and locate weeds within fields and that is already very helpful. Agreeing criteria and operating speeds is a key need to enable wider deployment of all technologies.

Temporal selectivity enables treatments to be made when crops are more tolerant or weeds more sensitive. Just as pre-emergence herbicides are widely used, such approaches should be considered for non-chemical approaches.

Crop and weed tolerance is critical for herbicides, but also for non-chemical approaches. Information on what it takes to kill a weed and what it takes not to kill a crop will be vital considerations in enabling current and new non-chemical approaches, but also in prioritising herbicide options. The screening of herbicides for minor crops could be advanced, and cost minimised, through a more strategic approach that considers weed and crop tolerance independently and enables a more focused approach to deliver quicker results. In parallel, the regulatory issues of using herbicides on a wider range of crops will need to be addressed and requires a combined grower, regulator and retailer approach. 

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