10 Strategies for Managing Resistant Weeds in Cotton

Marestail weed in cotton
A proliferation of marestail, a weed that is resistant to multiple classes of chemistries.

Cotton growers who take an integrated approach to weed control – before resistant weeds become an issue – can avoid the headaches and ensure long-term success in protecting crop yields.

Over-reliance on a single weed-control method causes resistant weeds to develop, jeopardizing herbicide-tolerant systems and future planting. Growers then face additional expenses, such as unplanned herbicide applications, additional cultivation and manual removal. In some extreme cases, total crop loss is the ultimate cost.

Many aggressive and yield-robbing weeds such as Palmer amaranth, waterhemp, marestail, lambquarters and common and giant ragweed are resistant to multiple classes of chemistries. But integrated weed management techniques – adopting a tankmix of multiple, effective herbicide sites of action, as well as cultural practices such as crop rotation and mechanical weed control – are effective in reducing problems with herbicide-resistant weed biotypes.

It is best to use multiple practices to manage or delay resistance, as no single strategy will be completely effective on its own.

Weed Resistance Best Management Practices

Resistant weed biotypes exist in every field. The only way to avoid selecting for them and increasing the spread of resistant populations is through a program of best management practices (BMPs), which set a standard of zero tolerance to keep weeds from going to seed.

Though new in-season traits are available to control weeds, no new sites of action are available to ensure the durability of existing herbicides. It is imperative to use BMPs that will sustain existing chemistries to help protect crop yields. These include:

  • Crop rotation
  • Rotation of herbicide-tolerant traits
  • Use of multiple, effective herbicide sites of action
  • Knowledge of fields and the weeds affecting them
  • Starting with clean fields
  • Staying clean by using residual herbicides whenever possible
  • Applying herbicides correctly
  • Controlling weed escapes
  • Adopting a zero tolerance approach to seeds in the soil bank
  • Cleaning equipment

Bayer Solutions

Bayer has a broad portfolio to combat tough-to-control and resistant weeds. A well-thought-out herbicide program, using multiple sites of action, should be implemented to sustainably manage weeds. Before applying any herbicide, please read the entire label for the best possible results and to confirm that the product is effective on the weeds you wish to control. Not every product is suitable for every situation, and use of the correct application technique will ensure the best results.

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