HERBICIDES

 

When planning a weed control program, products should be chosen from different mode of action groups to control the same weed either in successive applications or in mixtures.

A general guideline for the rotation of chemical groups should consider:

  1. Avoid continued use of the same herbicide or herbicides having the same mode of action in the same field, unless it is integrated with other weed control practices.

  2. Limit the number of applications of a single herbicide or herbicides having the same mode of action in a single growing season.

  3. Where possible, use multi-mode of action herbicides, which apply a different mode of action on the same target weeds.

  4. Use non-selective herbicides to control early flushes of weeds (prior to crop emergence) and/or weed escapes.

From experience, we can conclude that rotation of herbicides alone is not enough to prevent the development of resistance. To retain these valuable tools, the chemical rotation explained must be employed in association with at least some of the other weed control measures outlined.

 Herbicide Mixtures

 

Mixtures can be a useful tool in managing or preventing the establishment of resistant weeds.

For chemical mixtures to be effective, they should:

  1. Include active ingredients which both give high levels of control of the target weed; and,

  2. include active ingredients from different mode of action groupings.

The grower should also:

  1. Know which weeds infest his field or non-crop area, and, where possible, tailor his weed control program according to weed densities and/or economic thresholds;

  2. Follow label use instructions carefully; this especially includes recommended use rates and application timing for the weeds to be controlled;

  3. Routinely monitor results of herbicide applications, being aware of any trends or changes in the weed populations present;

  4. Maintain detailed field records so that cropping and herbicide history is known.