If broadleaf weeds become resistant to herbicide, soybeans yield will be affected

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What Can Be Done to Minimize Herbicide Resistance?

Bob Herzfeld, Product Manager
Bob Herzfeld, Product Manager

A recent CropLife article discusses the alarming increase in herbicide-resistant weeds in agriculture. The process of how weeds become resistant to herbicides is not always obvious, but it does come down to the fact that the weeds encountered active ingredients and did not get killed by it. 

In an earlier blog post, we discussed ways to optimize pre-emergence applications. One of the things to remember is to make sure that the herbicide is applied correctly at any time. That includes the usage of adjuvants for proper deposition, spreading, penetration, and water conditioning. If the pesticide does not make it to the target plant in the right amount, the weed can survive, and future populations can form genetic resistance against the chemical.

The CPDA (Council of Producer and Distributors of Agrotechnology) presented insights during the webinar ‘Adjuvants Support Responsible Agronomy In Good Years & Bad And Input Trends And Implications For 2021’ into how adjuvants support responsible agronomy. During that presentation, they highlighted how adjuvant selection contributes to the performance of pesticides based on empirical data.

Adjuvant selection has a vast influence on crop protection products’ performance. The table above shows the decrease in performance in various situations. Selecting the wrong type of adjuvant reduces pesticide performance and can even lead to an increased risk of crop injury.

This performance information is based on empirical data collected by Joe Gednalske and his team. Joe Gednalske is the former Director of R&D for WinField United’s Innovation Center and currently consults for the CPDA. They have conducted hundreds of field research tests over twenty years. They were able to summarize the “Value of Adjuvants” over the years of testing. Their conclusions were backed up by Rick Zollinger, NDSU Extension Service and Weed Specialist, saying, “WinField United research mirrors what I have observed in NDSU field trials.” Also, university researchers in Canada have agreed with WinField’s conclusions. The results shows that making mistakes in adjuvant selection can be substantial.

Image on the left: no herbicide applied. Center image: herbicide applied without adjuvant. Image on the right: herbicide applied with the recommended adjuvant.
Image on the left: no herbicide applied. Center image: herbicide applied without adjuvant. Image on the right: herbicide applied with the recommended adjuvant.

Adjuvants can help with the proper deposition, spreading, and penetration of the pesticide in the target. Also, adequate water conditioning can help prevent herbicide resistance as hard water ions, or the wrong pH can render the pesticide less effective.

Why is deposition important in preventing herbicide resistance?

To optimize herbicide effectiveness, it is crucial to maximize on-target deposition. A pesticide that does not make it to the intended location or rolls right off will not be able to penetrate the leaf of the weed and do its job.

Why is the spreading of pesticides essential?

When a pesticide is sprayed on a plant, ensuring that the spray spreads out evenly helps the active ingredient cover a large leaf area. This enables efficient and fast penetration of the active into the leaf, enabling herbicides to enter the plant system quickly.

Why is good penetration of the pesticide necessary?

If the pesticide cannot make it through the cuticle of a plant, it will not reach the critical pathways in the plant. That means the pesticide will not be able to affect the plant growth negatively. Different plants have different cuticles (hard, waxy, or hairy), and environmental circumstances affect herbicide absorption. Adjuvants come with a broad range of properties that work best under unique conditions, ensuring the proper pesticide efficacy.

Adjuvants are an essential part of any weed management program and can make or break its success.

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