In response to potential loss of herbicides due to EU Directives and regulations and other environmental pressures, the project is carrying out basic and applied research to facilitate the adoption of targeted patch spraying of grass weeds and selected broad leaved weeds in arable fields in the UK. Machinery and systems are already available for patch spraying. The barrier to adoption is knowing where the patches are located with the precision required. This TSB-cofunded project is, therefore, developing an innovative machine vision system to automate weed mapping during normal field operations such as fungicide spraying or combine harvesting. The project has a strong focus on black-grass, the dominant grass weed of winter wheat although the system is also expected to map wild-oat, barren brome and rye-grass. Late season mapping is being carried out to geo-locate patches where significant seed shedding occurs as these will be key problem areas for black-grass in next season’s crop. An important hypothesis of the research is that late season mapping provides a sound basis for patch spraying of pre-emergence herbicide. The use and economics of applying herbicides to these patches via conventional sprayers for site specific weed management will be evaluated. Projected costs and benefits predict that the system will not only control weeds at lower cost and with lower herbicide inputs, beneficial to both the farmer and the environment, but mapping late in the season will allow early detection of herbicide resistance.