Which practice helps slow the development of resistance to herbicides?

Which practice helps slow the development of resistance to herbicides?

• A. Use herbicides with different modes of action for subsequent applications.
• B. Increase the number of herbicide applications this season.
• C. Use the same mode of action for all applications.
• D. Apply herbicides only where weeds are present.

Answer: (A)

Rotating or mixing herbicides with different modes of action slows resistance by changing the target the weed population is challenged to adapt to. When the same mode of action is used repeatedly, survivors—those with resistant traits to that specific target—live on and reproduce, gradually shifting the population toward resistance. By using different modes of action in subsequent applications, or combining them in tank mixes, you increase the chance that individuals resistant to one action will still be controlled by another, keeping most weeds susceptible overall. This spreads the selection pressure across multiple targets and reduces the likelihood that a weed carrying resistance to all of them will dominate. In practice, this approach is most effective when paired with correct timing, proper rates, and integration of cultural controls. Using the same mode of action for all applications, increasing the number of applications with the same mode of action, or applying herbicides only where weeds are present don’t provide the same protective effect against resistance development.

Rotating or mixing herbicides with different modes of action slows resistance by changing the target the weed population is challenged to adapt to. When the same mode of action is used repeatedly, survivors—those with resistant traits to that specific target—live on and reproduce, gradually shifting the population toward resistance. By using different modes of action in subsequent applications, or combining them in tank mixes, you increase the chance that individuals resistant to one action will still be controlled by another, keeping most weeds susceptible overall. This spreads the selection pressure across multiple targets and reduces the likelihood that a weed carrying resistance to all of them will dominate. In practice, this approach is most effective when paired with correct timing, proper rates, and integration of cultural controls. Using the same mode of action for all applications, increasing the number of applications with the same mode of action, or applying herbicides only where weeds are present don’t provide the same protective effect against resistance development.