Herbicide-Resistant Weeds: Looking Below the Soil Surface

Sarah Kezar

2020-2023 FFAR Fellow

Texas A&M University

  • Next Generation Crops

Farmers have been fighting weeds for millennia. While the number and efficacy of tools to combat weed pressures have vastly improved, weed resistance is a continuing problem for crop productivity and profitability. Even when weeds appear to be destroyed, their seeds linger, hidden in the soil seedbank. A seedbank is the living memory of resistant weed species and the source for future weed infestations. They are the most impactful robber of yields worldwide and particularly destructive for cotton, which is the focus of my research.

In cotton fields, weeds such as Palmer amaranth can establish themselves even after a late-post herbicide application, due to their open canopies. The presence of weed seed “escapes” from herbicide application are unavoidable. These late-season escapes could be low in frequency and may not lead to crop yield loss in the current season but can add substantial amounts of weed seed to the soil seedbank, resulting in future weed problems. Palmer amaranth is a prolific weed seed producer: a single female Palmer amaranth can produce up to a million seeds! In addition to increasing seedbank size, these late-season escapes contaminate cotton lint and affect market quality.

Seedbank management is a key aspect of herbicide-resistant weed management. My research investigates reducing the amount of seeds Palmer amaranth can produce and inherently decreasing future competition with the cotton crop. After all, we need to protect the fabric of our lives, right? If we want to aid the cotton crop to have a fighting chance against this highly competitive weed, we need to minimize seed production and seedbank addition to sustain the utility of existing herbicides.

What if we found ways to stop a female Palmer amaranth from producing a million seeds? We know that the proclivity of a weed is influenced by the environment experienced by the mother plant. My research targets Palmer amaranth females and their seeds by using tricky tactics like sterility hormones, desiccating the cotton early in its growth and even the use of LED lights. This research is expected to lead to the development of integrated strategies that minimize seedbank additions from Palmer amaranth escapes, thus complimenting herbicide-based tactics used in-season and helping improve the longevity of available herbicide tools. The tactics evaluated in my research will also support the implementation of zero-tolerance programs for Palmer amaranth management in US cotton production. A zero-tolerance program helps prevent resistant weeds from going to seed at all by implementing a variety of strategies for maximum integrated weed management. Overall, the outcomes of this project are expected to help suppress long-term population growth of Palmer amaranth, reduce weed control costs and improve the economic and environmental sustainability of cotton production in the United States.

I am excited to work with Cotton Inc. as my FFAR Fellows industry sponsor. Cotton Inc. is at the forefront of supporting scientists and researchers across the supply chain, with efficiency and environmental sustainability in mind, to continually evolve the ways cotton is grown and manufactured. Mentorship by scientists at Cotton Inc. will not only help me better understand the cotton industry, but also give me tools to relay this work and future work, to others. The foundation of this research relationship and the creative liberties I can take in my research to explore seedbank solutions would not be possible without the FFAR Fellowship. I am sincerely grateful for the Fellowship’s focus on cutting-edge scientific research and the development of collaborative skills that agricultural scientists need to discover and implement high-impact solutions.

2020-2023 FFAR Fellow, Sarah Kezar

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