The invention relates to a modular system for weed control for a rail vehicle. The modular system has a control unit for producing control signals for controlling valves and mixers in a separate herbicide and mixing module and for producing a second set of control signals for controlling valves of a nozzle rod. The herbicide and mixing module has a container for holding different herbicides and electrical connection elements for connections to the control unit. Furthermore, a nozzle rod is present, which is fitted with a nozzle set, in order to spray herbicides of the herbicide and mixing module. In addition, a camera module is present, which produces a weed signal in response to the detection of a weed, in order to control the spraying of the herbicides. The camera module is at such a distance from the nozzle rod that, despite high speed, there is sufficient time to provide the herbicide at the nozzles.