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We are all familiar with the Twelve Days of Christmas. Well, we should all be just as familiar with the twelve best management practices (BMPs) for managing weed resistance.

The ‘Take Action’ website listed these 12 BMPs that are useful to remember. Below is a link to the ‘Take Action’ website and a PDF of the BMPs. The additional commentary on 12 BMPs was added by Eric Ifft, Customer Business Advisor with Bayer CropScience, and is reprinted here with permission.

12 Best Management Practices for Managing Weed Resistance

1. Understand the Biology of the Weeds. This is the very start of managing this issue. Do you know the strengths and weaknesses of the weed species you are dealing with? Weeds can vary on such things as:

• Germination timing: Do they all germinate at once or over time? Do they germinate early, or later in the season?
• Germination depth: Do they germinate from deep or shallow?
• How fast do they grow?
• How long do the seeds live in the soil?
• Are there any resistance issues to any chemistries?

2. Use a diversified approach toward weed management. Focus on preventing weed seed production, thereby reducing the number of weed seeds in the soil bank.

• One waterhemp can make hundreds of thousands of seeds. Therefore, leaving just one weed that goes to seed in a field can change the waterhemp pressure in one year.

3. Plant into weed-free fields and then keep fields as weed free as possible.

• Waterhemp can grow 1 – 2 inches a day and we should control them before they are 4 inches. Stop weeds when they’re small – under 4 inches -- or you’ll never catch up.”

4. Plant weed-free crop seed.

• I don’t think we have anything to worry about with seed corn or soybean seed, but watch out if you plant pollinator plots. I found Palmer amaranth in 3 pollinator plots this year!

5. Scout fields routinely.

• If you know you have a high waterhemp population, it would not be a bad idea to scout weekly. Remember, if they germinate the day after you scout they could be
  6 – 8” tall a week later.

6. Use multiple herbicide modes of action that are effective against the most troublesome weed or those prone to herbicide resistance.

• All studies show you are 83% less likely to develop resistance to a herbicide mode of action if you have two or more effective MOA’s in the tank.

7. Apply the labelled herbicide rate as recommended for weed sizes.

• Full rates and the correct adjuvant package are crucial for effective weed control.
• Did you know that for every 2 inches, the number of growing points on a waterhemp doubles? Therefore, we must spray full rates.

8. Emphasize cultural practices that suppress weeds by using crop competitiveness.

• I see a trend toward narrower rows and higher populations in corn. That would help provide shade quicker.

9. Use mechanical and biological management approaches where appropriate.

• Tillage is becoming more and more important.

10. Prevent field-to-field and within field movement of weed seed.

• Will we start having to clean equipment? Something to think about if you know you have resistant weeds on one farm.

11. Manage weed seed at harvest and after harvest to prevent a buildup of the weed seedbank.

• With waterhemp management it is all about managing weed seed. This means you should not let even ONE waterhemp go to seed in your field. Are you willing to walk out in a field and remove that one waterhemp?

12. Prevent an influx of weeds into the field by managing field borders.

• My theory here is that herbicide-resistant waterhemp is blowing out of combine heads as we drive around at harvest. That is why they always start in the end rows.

Agronomist Daniel Davidson, Ph.D. posts blogs on agronomy-related topics. Feel free to contact him at djdavidson@agwrite.com or ring him at 402-649-5919.