What is a potential negative outcome of using a single herbicide repeatedly?

Using a single herbicide repeatedly can lead to weed resistance, which is a significant concern in agricultural and horticultural practices. When a herbicide is applied continuously to control weeds, the susceptible weed populations are eliminated, while those individuals with natural resistance to the herbicide survive and reproduce. Over time, this results in a population of weeds that can no longer be effectively controlled by that particular herbicide. This can create a cycle where higher doses or different, often more expensive, products must be used to manage the resistant weeds, complicating weed management strategies and potentially leading to greater long-term costs and environmental impact.

The other options, like inconsistent weed control or increased herbicide costs, can result from various factors but are not as directly linked to the issue of resistance development as the repeated application of a single herbicide is. Reduced environmental impact is typically not a consequence of herbicide resistance; instead, it often leads to negative ecological effects as resistant weeds may require more interventions, thus increasing chemical usage and impacting the environment.