Understanding Weed Growth

Why are some weeds more prone to resistance? What makes some weeds more competitive than others?

Two questions, one answer. Weed biology.

Understanding weed biology is essential to effective weed management. Because that’s the kind of knowledge it takes to take control of the most troublesome weeds.

By understanding weed emergence patterns, growth and reproduction, you can develop management strategies that target the life stages most sensitive to management.

Emergence patterns

Understanding weed-emergence requirements and emergence patterns helps determine the appropriate timing and selection of control measures to prevent the escape of resistant or potentially resistant weeds.

What you should know:

  • Early-emerging weeds are more competitive with crops.
  • Late-emerging weeds cause less interference with the crop and experience lower reproductive success than early-emerging cohorts; but seed production from these late-season escapees, even at low levels, must be considered when developing resistance-management strategies.
  • Delayed emergence or emergence over an extended period can allow later weeds to escape control measures, especially when in-crop herbicide applications lack residual control.
  • Weeds that emerge throughout the growing season require weed management tactics to be extended well beyond crop establishment and will require multiple passes through the field.

Reproductive and life cycle

Weed management centers on preventing weed reproduction. Understanding reproduction stages can help you control weeds before they go to seed. Some weeds have very rapid reproduction cycles, and the window for control is very short.

Keep in mind:

  • Annual weeds are more prone to resistance than perennial weeds.
  • Weeds that cross-pollinate are more prone to resistance.
  • Although a shorter reproductive development ensures reproductive success and seedbank replenishment, an extended flowering period provides greater opportunity for the spread of resistance genes via pollen movement in outcrossing weed species.
  • Delayed emergence typically accelerates the onset of reproductive development.

Supporting content

Weed Emergence Sequences