Abstract
This project assesses the risks posed to sustainable management of agricultural weeds by i) proposed changes to EU pesticide legislation which will result in the loss of many currently used herbicides and ii) increased invasions of novel agricultural weeds as a result of climate and other environmental change. In the last 30 years, agricultural weed control has been dominated by the use of herbicides. Herbicides are easy to use, highly effective and have contributed significantly to rising agricultural yields in the UK and worldwide. However, there are concerns that excessive reliance on agrichemicals has had adverse environmental effects and EU and UK government legislation is increasingly moving to limit the use of the most hazardous herbicides. It is envisaged that recent further changes in EU legislation will result in the further loss of approximately 15% of currently registered pesticides. At the same time as herbicide regulations are tightening, there is increasing incidence of herbicide resistance in weeds. Herbicide resistance evolves in weed species following frequent exposure to a single herbicide mode of action. Where resistance is already prevalent in weed populations, it is likely that new regulations will remove some important alternative herbicide modes of action. Where farmers are fighting resistance with judicious rotation of many herbicide modes of action, these efforts will be hampered by a reduction in the number of herbicides at their disposal. Given these concerns, future weed management strategies will need to integrate a larger number of practices, that do not rely solely on herbicides, in order to deliver sustainable control of weeds. A key objective of this research is to develop a computer model that will predict the impacts of changes in herbicide availability on the control of weeds in UK arable cropping rotations. As it will not be possible to consider all weeds, we have chosen to focus on blackgrass, the most severe, widespread and herbicide-resistance prone weed species in the UK. Once the model has been used to demonstrate the impacts of changing pesticide legislation, a series of analyses will be performed to consider how weed management can change in the future to compensate for herbicide losses and to make future weed management more sustainable, environmentally benign and less prone to development of herbicide resistance. A key element of these changes will be to incorporate more cultural, physical and biological weed control options. This modelling-based project will help Defra to quantify the impact of changing legislation on weed management. By providing an indication of what alternative weed management strategies are likely to be required in future, the project will help to direct future Defra-funded weeds research. In particular, the development of alternative weed control strategies will require research to better understand the biology of weeds, so that this knowledge can be used to inform their control. The second element of this project will consider the potential for new weeds to invade and spread in the UK. There is increasing evidence that some weeds that are serious agricultural problems in their native and introduced ranges in Europe and North America are increasing their incidence and distribution in the UK. The project will examine the evidence that these species are spreading in the UK and will consider how this spread may be exacerbated by climate and environmental change. Recommendations will be made for further research to quantify and mitigate future risks of invasion.
United Kingdom