Repeated exposure of a weed population to any herbicide in isolation may have two effects. The weeds species that are not controlled by the herbicide will dominate the population (species shift) and pressure will be exerted on the population to select any resistant individuals that may be present (herbicide resistance).
The development of both species shift and herbicide resistance can be effectively managed by the practice of Integrated Weed Management (IWM). The principles of IWM are that weed management should not rely on one single form of control. In practical terms IWM means the development of a weed management program that uses a combination of preventative, cultural mechanical and chemical control practices.
An IWM system uses various weed control methods Source - WEEDPak
IWM provides a framework for effective and sustainable weed management that ultimately prevents weeds from propagating (setting seed or vegetatively reproducing). This will lead to a reduction in the weed population over time, resulting in reduced crop competition and an improvement in crop productivity.