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Timing Herbicide Application

July 21, 2017

An effective weed control program depends heavily on well-timed herbicide applications, in addition to cultural practices. Failing to apply a herbicide at the right time could result in wasted input costs, weed infestations and reduced yield.

Factors determining the timing of post-emergence herbicide applications:

  • Crop growth stage: Follow labels to avoid crop injury.
  • Weed growth stage: Scout fields regularly and treat weeds before they reach 4” in height.
  • Weather: Pay attention to weather, and refer to labels for required application conditions.

This agronomic image shows waterhemp.

Overlapping residuals can help keep driver weeds, such as waterhemp and Palmer amaranth, down. As waterhemp grows, it develops multiple points of growth, which become increasingly hard to control with a herbicide. Scout fields regularly after herbicide applications to ensure that all points of growth on each weed are treated.

The University of Illinois also reminds growers to use herbicides with multiple, effective modes of action on target weeds. Growers using a two-pass system in corn can follow their foundation rate of Acuron® (groups 5, 15 & 27) or Acuron Flexi (groups 15, 27) corn herbicide with the remaining rate. Halex® GT corn herbicide (groups 9, 15 & 27) can also be applied post-emergence and brings an additional mode of action to the table.

Soybean growers can follow their pre-emergence herbicide applications with Prefix® (groups 14, 15) residual herbicide and/or Flexstar® GT 3.5  (groups 9, 14) herbicide for a robust two-pass herbicide program.

For more weed management tips, take the Resistance Fighter® Weed IQ Quiz.

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