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Glyphosate in Mixes with other Postemergence Herbicides (05/12/16)

Glyphosate is a systemic herbicide that performs best when applied in larger spray droplets and at lower water volumes (5-10 gallon per acre) during the heat and humidity of the day to increase herbicide absorption into the plant.

Glyphosate in Mixes with other Postemergence Herbicides

Glyphosate is a systemic herbicide that performs best when applied in larger spray droplets and at lower water volumes (5-10 gallon per acre) during the heat and humidity of the day to increase herbicide absorption into the plant. Apply glyphosate in combination with ammonium sulfate (AMS) at 8.5 lb. /100 gallons water carrier and non-ionic surfactant (NIS), depending on the formulation. AMS enhances glyphosate absorption and translocation and deactivates antagonistic hard water salts. NIS improves retention of spray droplets and improves control of hard-to-wet species.

Glyphosate frequently is applied in mixes with other herbicides to increase spectrum of weed control, provide an additional site of action for control of tough weeds and/or to provide soil residual control. In this case, glyphosate must be applied to maximize efficacy of tank-mix partners. For example, glyphosate applied with contact herbicides must be applied in small spray droplets at greater spray volumes (10 to 20 GPA). Most herbicides applied with glyphosate are oil soluble and are applied with oil adjuvants (crop oil concentrate and methylate seed oil) that antagonize glyphosate. High surfactant methylated seed oil (HSMOC) style adjuvants contain a greater concentration of surfactant than crop oil concentrate (COC) and methylated seed oil (MSO) and enhance oil soluble herbicides without decreasing glyphosate activity. Herbicide mixes maybe applied later in the day, in some situations, to avoid crop injury. AMS should always be applied in mixes containing glyphosate and other herbicides.

 

Rich Zollinger

Extension Weed Specialist

&

Tom Peters

Extension Sugarbeet Agronomist; NDSU & U of MN

 

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