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Glyphosate Resistance Management

Glyphosate Resistance Management

Glyphosate Resistance Management

A Good Year to Emphasize Glyphosate Resistance Management Given the Supply Chain Challenges with Glyphosate. 

If you’ve grown used to glyphosate as your front line weed control for alfalfa establishment, this is a good time to consider making a change.

Many experts are suggesting that 2022 weed control strategies should emphasize glyphosate resistance management given the supply chain challenges with glyphosate.  It’s a good time to strongly consider herbicide rotation and application of alternative herbicide MOAs.  It can be tempting to stretch a limited supply of glyphosate by reducing application rates.  However, using a cut-rate of glyphosate just accelerates resistant weed development by selecting for partially resistant individuals among the weed population in your fields.

Before planting alfalfa it’s important to get established weeds under control through tillage or a burndown herbicide application for no-till or minimum-till seedings.  Paraquat is generally recommended as the best glyphosate substitute for early burndown before crop emergence.  Paraquat is a broad spectrum contact herbicide and should be applied with enough water for good coverage, generally 15 gallons per acre or more.  While Paraquat can burn down pre-existing weeds at planting, like glyphosate, paraquat provides no residual weed control.

It’s important to control weeds that emerge soon after planting.  Weeds that grow unchecked right along with young alfalfa seedlings, are going to compete the most with alfalfa during the establishment phase.  Therefore an additional herbicide for pre-emerge or early post-emergence weed control should be a strong consideration.

Glyphosate Resistance Management

Good weed control during the first six weeks of growth is a critical period for obtaining good alfalfa stand establishment. Recently emerged alfalfa seedlings are approaching the unifoliate leaf stage, and the first trifoliate leaf will follow soon.

The University of Nebraska conducted a study to evaluate weed control, alfalfa yield, and net return outcomes comparing glyphosate versus other commonly used herbicide progams for alfalfa establishment.  Among the conclusions were ”First-harvest forage where no herbicide was applied was estimated to contain 62% weeds, where glyphosate was applied at the unifoliate growth stage approximately 39% weeds, and where imazamox {Raptor® herbicide} was applied approximately 21% weeds.”  Furthermore when taking into account the Roundup® Ready seed tech fees, “removing the majority of the weeds with a conventional weed control program or a glyphosate-based program can both be equally economical to the alfalfa producer.”

Researchers concluded that Imazamox {Raptor} application provided the same net returns as a single application of glyphosate when considering the full cost including Roundup® Ready seed tech fees.  Net return declined when a second application of glyphosate was required to control later emerging weeds as a result of the lack of residual control from glyphosate. The single application of Imazamox {Raptor} provided residual weed control and better net returns when it came to late-emerging weeds.  Pursuit® herbicide is another herbicide labeled for early post-emergence application.  Pursuit also provides residual weed control and is in the same herbicide MOA class as Raptor.

Click here to see the full report….. Evaluation of Glyphosate-Tolerant and Conventional Alfalfa Weed Control Systems during the First Year of Establishment

Click here for more planting and establishment tips in alfalfa….Be Patient and Prudent when Planting Alfalfa

Click here to review herbicide options for alfalfa (make sure to read and follow applicable herbicide labels)….Rotate Herbicides in Alfalfa to Avoid Weed Resistance