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Soybean growers: Your guide to fight weed resistance

March 18, 2016

For many growers, pest resistance is a nightmare come true. Whether it’s insects, diseases or weeds, pressures on soybeans seem to be getting stronger each year despite evolving management practices. However, these threats are not indiscriminate. Failure to address any one of these threats when building your seasonal management plan will directly cause a breakdown in profitability in your soybean fields.

Whether resistance has already developed in your fields or you fear that it will soon, we’ve laid out a point-by-point guide to help you address one of the most challenging types of pest resistance: herbicide resistance.

Start clean with tillage or an effective burndown and a pre-emergence residual herbicide application

  • Too many growers rely solely on post-emergence herbicides. Hitting weeds before they emerge and beginning a season with clean fields is paramount to keeping weeds at bay.

Use a two-pass pre- and post-emergence system

  • Two-pass systems ensure that you are addressing any and all weed presence. When applying herbicides, make certain that you are using the full recommended rate. Applying less than the recommended rate may contribute to resistance.

Employ multiple effective modes of action with overlapping efficacy

  • Herbicides with multiple effective modes of action are more difficult for weeds to resist. If you only use a single chemistry, you are unintentionally selecting for resistant weeds. By using mixtures with residuals, you can delay resistance issues.

Use a diversified management program

  • Beyond selecting the right herbicides, fighting weeds with other management approaches contributes to a well-rounded, full-farm approach. One management tactic instead of a combination of tactics is less likely to be effective on weeds, per the University of Minnesota Extension. Cover crops, mechanical weed control and crop rotation are great tools to ensure you are attacking weeds from all angles. It’s important not to overlook these traditional agronomic tactics.

Reduce the weed seed bank

  • Remember not to allow weeds to grow uncontrolled in the off-season. Eliminating seed production will halt the development of a weed seed bank on your farm. Even after harvest, weeds may continue producing seed until the first frost, affecting future seasons.

Keep an eye on the objective

  • Weed management and yield protection, not just weed control, is the objective. A clean field one day does not mean that you have defeated the enemy. Managing the weed seed bank and fighting resistance for future seasons will ultimately lead to the highest return on investment and yields.

To fight weeds in your fields this season, Syngenta offers BroadAxe® XC and Boundary® herbicides for early-season weed protection. Both of these pre-emergence herbicides provide two leading active ingredients with multiple modes of action and work well in a two-pass program. For comprehensive post-emergence control, Syngenta recommends Flexstar® GT 3.5 herbicide. With two different modes of action, this herbicide enables you to fight weeds that are likely to develop resistance to glyphosate and/or ALS-inhibitors in glyphosate-tolerant soybeans.

When it comes to weed resistance on your farm, it’s important to respect the strength of the enemy. Applying less than the recommended herbicide rate or not employing a thorough management plan against weeds may contribute to their resistance. Follow this guide to ensure that your fields don’t become the next safe haven for resistant weeds.

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