Herbicide Resistance

Field trial comparing timing of soybean weed management
Figure 1. (left) Soybean without preemergence herbicide at V6 stage and (right) soybean with preemergence herbicide at V6 stage.

Preemergence Herbicides Delayed the Critical Time for Weed Removal in Soybean May 16, 2018

Researchers tested two herbicide strategies in soybean to see how preemergence herbicides would delay the critical time of weed removal, likely reducing the number of herbicide applications needed in a season.

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The Rise of Multiple-Resistance in Nebraska’s Weeds and Effects Of Dicamba Micro-Rates on Sensitive Crops April 16, 2018

Weed resistance to herbicides is a global problem, which usually results from the repeated use of herbicides with the same mode of action. Simply said: “Weeds just got used to that mode of action and cannot be killed with that mode of action anymore.” Similar phenomenon is observed in medicine with disease resistance to antibiotics.

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Herbicide-Resistant Kochia, Palmer, and Waterhemp in the Panhandle: Distribution and Management April 9, 2018

Several field trials were undertaken in 2017 to look at options for controlling herbicide-resistant kochia, Palmer amaranth, and waterhemp in dry bean, corn, and sugarbeet. In addition over 80 kochia, Palmer amaranth, and waterhemp plants were collected for testing of herbicide resistance. Of these 50% of kochia and 13% of Palmer amaranth plants tested were resistant to field rates of glyphosate. While options are limited in the Panhandle, pairing crop rotations with herbicide programs using PRE and layby treatments provided effective control of key weed species.

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field pennycress post herbicide app
Figure 1. Survival of field pennycress due to application of burndown herbicide when the temperature was below 40°F for an extended time. (Photos by Amit Jhala)

Low Temperature and Frost May Affect Efficacy of Burndown Herbicides November 9, 2017

In many areas fall herbicide applications were delayed due to the late harvest. Applications can still be effective, depending on weeds present, temperature, rate of herbicide and additives used. The article offers recommendations for these late-fall applications and their importance, particularly for control of herbicide-resistant marestail.

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Palmer amaranth in corn
Figure 1. Glyphosate-resistant Palmer amaranth infesting corn field in south central Nebraska. (Photos by Amit Jhala)

Grower Q&A: Is this Herbicide-Resistant Palmer Amaranth? June 23, 2017

This week growers facing challenges with Palmer amaranth questioned whether it was due to the product, the environment and lack of rain, or a resistant weed. Several factors could be at play, notes a UNL weed scientist, who recommends starting with preemergence herbicides with residual activity to get the best control.

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Glyphosate-resistant marestail

Postemergence (Rescue) Herbicide Options for Control of Glyphosate-Resistant Marestail in Corn and Soybean May 24, 2017

Several factors have contributed to delayed applications and marestail escapes this spring. Includes recommendations for timely postemergence control in corn and soybean.

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Amit Jhala (left) and Debalin Sarangi
Amit Jhala (left) and Debalin Sarangi (right) along with other scientists detected pollen-mediated gene flow from glyphosate-resistant common waterhemp in Nebraska.

New Research Quantifies the Dispersal of Glyphosate Resistance Trait Through Pollen-Mediated Gene Flow May 18, 2017

The pollen-mediated gene flow was detected 38% to 54% at 0.1 meter distance and 5% to 9% at 50 meters, the highest distance tested in this study.

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marestail

Status of Herbicide-Resistant Weeds in Nebraska March 20, 2017

Nine weed species in Nebraska have now evolved resistance to at least one group of herbicides. Six weed species — common ragweed, common waterhemp, marestail, kochia, giant ragweed, and Palmer amaranth — have confirmed resistance to glyphosate. Rotate herbicide sites of action and weed control practice to avoid contributing to this trend.

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