Fall Management of Glyphosate Resistant Weed Species

Managing glyphosate-resistant weed species has made farmers think outside of the box when it comes to controlling the weed seed bank in their fields. Utilizing multiple IPM (Integrated Pest Management) strategies such as chemical, biological, and in some cases even mechanical control is needed to help control a certain weed species. It is a challenge to control weed species that are glyphosate-resistant, and growers must utilize different methods to help lessen the threat of yield loss of their commercial crop to these weeds.

Chemical Control

One specific example of a glyphosate-resistant weed for the Midwest is marestail. A single plant may produce up to 200,000 seeds, about 80% of which can germinate immediately after falling from a mature plant.¹ Another reason marestail is such a challenging weed is that it completes its lifecycle toward late summer and into early fall, meaning that it competes with corn and soybean plants the entire growing season for water and nutrient resources. A fall herbicide application of Sharpen^® Herbicide or Gramoxone^® SL 3.0 herbicide tank mixed with a growth regulator herbicide helps provide broad spectrum control of winter annuals and some perennial weed species. Residual chemistries such as Autumn™ Super 51 WDG Herbicide or metribuzin products may also help suppress glyphosate-resistant populations for next season’s commercial crop.

A fall application is unlikely to take the place of a spring burndown application, given that species like marestail are adapted to cool temperatures and will likely have some emergence prior to planting. Always read and check label requirements prior to making an herbicide application.

Biological Control

Utilizing cover crops is another great way to help diminish a weed species population in a field. The cover crop acts as a competitor to the weed species, while also helping to hold the topsoil in place from erosion. Early planting of cover crops is critical for control of weed species and can even be done while the commercial crop is still growing in the field.

These are only two control methods for helping to manage glyphosate-resistant weed species in the fall. As growers adapt to using different control methods, the more effective our weed management programs will be in the future.

Channel Agronomist
Tyler Vreugdenhil

Sources:

Jhala, A. 2018. Management of glyphosate-resistant marestail in fall. CROPWATCH. University of Nebraska-Lincoln. https://cropwatch.unl.edu/2018/management-glyphosate-resistant-marestail-fall

What is integrated pest management (IPM)? UC IPM. University of California Agriculture & Natural Resources. University of California. https://www2.ipm.ucanr.edu/What-is-IPM/#:~:text=IPM%20is%20an%20ecosystem%2Dbased,and%20use%20of%20resistant%20varieties.

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