How to use this tool.

The correct choice of a herbicide is dependent on at least three things: The current crop, the next crop (rotation restrictions), and the weeds you are targeting. Click on 'Herbicide Selection" and use the form to enter this information for your field. A list of herbicides registered in Montana for the conditions you specify will be generated. Current labels can be found by clicking on the herbicide name or find them at Crop Data Management Systems. Be sure to check and follow the label that comes with your purchased product before making an application.

Our intent is not to rank or recommend a particular herbicide, but to reduce the number of choices available to you by filtering out those chemicals that do not fit your crop, crop rotation interval, and weed spectrum.

Start the selection process by choosing the initial conditions of crop, rotation interval to the next crop and at least one weed. Click on "Build the Table" to generate a results table. You can add additional weeds by returning to the selection page (use your browser's 'back' button). This tool will suggest certain combinations or tank mixes, but be sure to check all labels before proceeding. We are not making a herbicide recommendation, but are helping you find the best solution for weed control in your cropping system.

'Post' indicates herbicide will be applied after the targeted weed has emerged. Typically this means the herbicide is absorbed through the plant foliage. Usually the crop is emerged also and is tolerant of the herbicide.

'Pre' indicates the herbicide will be applied prior to weed emergence and may also mean application needs to occur prior to crop emergence or even crop planting. Typically soil applied herbicides have some residual activity. Check the label for the specific timing required for the herbicide application.

Prices

The prices listed are an estimate of cost of product per acre and should be used for relative comparisons between products. These prices are compiled from published information from the University of Nebraska 2016 Weed Guide. We have used prices from North Dakota State University (NDSU) for chemicals not contained in that guide. Prices vary across regions, and are dictated by local economic factors. Use these prices as guidelines in your decisions for weed control.

Herbicide Resistance Management

The following strategies will reduce the risk of selecting for herbicide-resistant weeds:

  1. Rotate crops to keep any one weed species from dominating. Rotations that include row crops, small grains, and perennial forages are most effective.
  2. Include tillage as a weed management tool.
  3. Use cultural practices that increase the crop's ability to compete against weeds. Practices include using narrow rows to increase shading of weeds, fertilizing adequately to enhance vigorous crop growth, and controlling weeds when they are small.
  4. Do not use the same herbicide every year.
  5. Use herbicides with different modes and sites of action in successive years, and where possible, within a year. Mode of action refers to the chemistry or chemical name. Site of action refers to roots, shoots, or foliage. Some chemistries can be used as pre (usually root or shoot active), or as post applied (foliage active).
  6. Use short residual rather than long-residual (persistent) herbicides.
  7. Don't allow suspected herbicide resistant weeds to produce seed. Consider removing them by hand, tillage, or with a burndown herbicide even if some crop loss might occur.

If you suspect you have a weed that has developed herbicide resistance, please contact us or your county agent for further investigation.

Links to Weed Identification Websites and Apps