Which option best describes strategies to reduce herbicide resistance risk?

• A. Crop rotations
• B. Herbicide rotations
• C. Mixtures with different modes of action
• D. All of the above

Answer: (D)

Strategies to reduce herbicide resistance risk rely on reducing selection pressure on weed populations by using diverse, integrated management approaches. Resistance builds when the same mode of action is used repeatedly, allowing tolerant individuals to dominate. Crop rotations help because different crops and their associated weed-control programs change which weeds are favored and reduce reliance on any single herbicide. Rotating herbicides—using different modes of action over time—limits selection for weeds resistant to a particular action. Mixtures that combine herbicides with different modes of action provide multiple killing mechanisms in one pass, making it much harder for a weed to survive a treatment.

Using all of these strategies together creates layers of control and reduces the chance that any weed biotype will survive and reproduce, which is why employing all of the above approaches is the best practice.