In turf weed management, which approach reduces resistance development?

• A. Rely on one mode of action
• B. Avoid cultural practices
• C. Rotate herbicide modes of action, use preemergence and postemergence strategies, and integrate cultural practices
• D. Use only postemergence herbicides

Answer: (C)

The main idea here is reducing the chance for weeds to develop resistance by mixing strategies rather than relying on a single approach. Using different herbicide modes of action in rotation keeps weeds from being repeatedly exposed to the same target. That means a weed population is less likely to have or develop a mutation that lets it survive every treatment, so resistance develops more slowly. At the same time, using both preemergence and postemergence tactics helps control weeds at different stages: preemergence reduces the number of weeds that can establish in the first place, lowering overall selection pressure on any one herbicide and helping manage the seed bank. Adding cultural practices, such as proper mowing height, fertility, irrigation, and overseeding, strengthens the turf’s competitiveness, which naturally suppresses weeds and reduces the need for herbicides.

Relying on a single mode of action accelerates resistance because the same mechanism is used repeatedly, giving survivors a clear advantage. Avoiding cultural practices increases weed pressure and can lead to more herbicide use, which heightens selection pressure. Using only postemergence herbicides misses early control and continues to push resistance on a single mode of action. Putting these pieces together—rotating modes of action, combining preemergence and postemergence methods, and integrating cultural practices—provides the most robust strategy to keep weeds from becoming resistant.