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Post Grass Antagonism from Basagran (06/09/16)

Question: I have several dry pea fields that have weed skips. The main weeds are volunteer wheat and 2 to 4 leaf wild buckwheat.

Post Grass Antagonism from Basagran


Question: I have several dry pea fields that have weed skips. The main weeds are volunteer wheat and 2 to 4 leaf wild buckwheat. Peas are at 3 to 4 node. I was planning to use Select Max at 9 fl oz./A and Basagran at 1.5 pints/A. Have you seen this tank mix used? I plan to add NIS at 0.25% v/v.

Answer: Basagran and other postemergence herbicides used in broadleaf crops can antagonize POST grass herbicides when mixed together. This antagonism is addressed in the comments in the top portion of page 27 in the ND Weed Control Guide where it refers to POST grass herbicide. Basagran may antagonize Select but the antagonism can be reduced by following the instructions on page 27:

“Grass control is reduced by tank mixtures or close interval application of POST broadleaf control herbicides. Antagonism generally can be avoided by applying a higher rate of grass herbicide or apply the grass control herbicide 1 or more days before or 7 days after the broadleaf control herbicide.”  Addition of AMS may also help reduce the antagonism from broadleaf herbicides.

Basagran is formulated as a Na salt. When Basagran is mixed with POST grass herbicides the Na from the Basagran can bind with the POST grass herbicides and cause reduced weed control similar to when cationic minerals in hard water antagonize glyphosate and most other postemergence herbicides.

With reference to wild buckwheat control, not many soybean, dry bean, or pea herbicides control wild buckwheat. The greatest activity occurs when Basagran is applied in split applications separated by 10 to 14 days, applied to small wild buckwheat that is not vining, applied in high spray volume (>15 gpa), and applied with an MSO adjuvant. See paragraph E3 on page 81 in the weed guide for data on split applications of Basagran and use of an MSO adjuvant.

Rich Zollinger

Extension Weed Specialist

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