Follow These 3 Steps to Simplify Your Herbicide Selection Process

Tracy Pell

Nov 26, 2018

Every field needs the right crop plan to maximize efficiency and profitability, and there are many parts and pieces that make up a complete and successful crop plan. The weed control portion of your crop plan should include several simple and straightforward steps to finalize an acceptable weed control strategy.

1. Positively ID weed species within each field.

Focus on the weeds that created problems for you this year, and determine the crop to be grown next year. Many herbicides can be used with several different crops, but there are some herbicides that are crop specific.

2. Crop safety matters.

Understanding variety characteristics and their herbicide interactions will help you to determine the best herbicide choice. Don’t skip over crop safety in the herbicide selection process.

3. What were last year’s weed populations?

You should estimate the seed bank to be produced next year. For example just one Palmer Amaranth plant can produce 500,000 seeds. If you were to get 99.9 percent control, there would still be 500 Palmer Amaranth plants per acre remaining.

4. Are they annual, biennial, or perennial weeds?

Which weeds were a factor in your final yields last year? Knowing the weed’s life cycle helps you in the timing of control to be applied and in herbicide selection.

5. Are your weeds resistant to certain modes of action?

For example, if the weed you are trying to control is resistant to acetolactate synthase (ALS) inhibiting herbicides, use another mode of action to get acceptable control. It’s possible that ALS herbicides may still be the best choice to give you good control of the other weed species found in the same field, so you might think about whether tank mixing herbicides could work for you to get more weed control. Be sure to check the compatibility of the herbicides to be tank mixed.

6. Timing your application for the best control of each weed species.

Winter annual weeds should be treated in the fall unless tillage to remove them is planned for early spring. Oftentimes, less expensive growth regulators can be applied for broadleaf control in the fall with reduced risk of off target damage. Keep in mind that application timing can also affect the price of the herbicide program, depending on when you plan to buy your chosen chem.

7. What herbicide rates did you use this year?

Did you receive a level of weed control that you were satisfied with this year? If your herbicide plan includes more of the same herbicides you used this year, purchasing them now at lower prices could save dollars and eliminate the possibility of searching for them next spring.

8. Overlap residual herbicides for troublesome weeds with extended germination.

Consider making an application of overlapping residual herbicides for those troublesome weeds that have extended germination periods. This can be a reliable way to achieve good control on difficult, prolific weed species — the goal is to keep the field weed-free until crop canopy.

9. Consider alternative products and methods upfront.

Some alternative products may help to control your weeds more efficiently. Combining mode of action herbicides can also help to improve your weed control results — this is simply good weed management. Ask yourself if tillage could be implemented to improve weed control.

10. Getting “control” versus “suppression.”

Always read the herbicide label to be sure it says “control” of the weed. Select a herbicide that states it can help to control the specific weeds you have present. When the label claims “suppression” of the weed you must expect some weed escapes that may be difficult to deal with. Selecting the least expensive herbicide may not be the most cost effective in the long run.

11. Full rates help to reduce weed escapes.

By applying reduced rates of herbicide, you may be contributing to building up weed resistance to that herbicide. You should expect reduced weed control if you apply a reduced rate of herbicide. This can cause you to need an additional weed treatment application (which would increase your herbicide cost) and give you less effective weed control than you’re looking for.

12. Consider any chemical carry over issues.

Consider any chemical carry over issues that might be possible from past herbicides you have applied, as well as from the herbicides you’ve selected for next year. Be sure you know the Pre Harvest Interval (PHI) for each of the products you’ve chosen, and make certain that these products fit into your future cropping plan.

13. Always apply based on the label use for each product.

Always read and follow the label use directions before using any ag chemical. The bottom line is that the label is the law.

By following these steps, and with the help of your agronomic team, your herbicide plan can help you to achieve maximum weed control, even from the most difficult weeds.

Tracy Pell

Nov 26, 2018