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Timing of Herbicide Applications is Critical for Effective Weed Control in Sugarbeet

by Dr. Jeff Stachler, U of MN Extension and NDSU Agronomist - Sugarbeet/Weed Science

Sugarbeets have emerged or are beginning to emerge. That means it is time to begin postemergence herbicide applications to sugarbeet. Timing of the first postemergence herbicide application is the MOST critical weed management tactic, regardless of the type of sugarbeet planted.

Conventional sugarbeets

For conventional sugarbeets, herbicides should be applied for the first time when weeds are in the cotyledon stage of growth and no larger than 1 true-leaf. A mixture of Betamix plus Nortron or Progress plus Stinger plus UpBeet plus Select plus methylated seed oil at 1.5 %v/v usually provides the most effective weed control. Consult the Sugarbeet Production Guide and/or the Weed Control Guide for specific herbicide rates regarding the micro and mid-rate programs and additional information, especially about mixing herbicides.

Apply the highest rate of Betamix or Progress based upon the stage of the sugarbeet at the time of the application. All sequential herbicide applications should be applied every 5 to 7 days or according to the growing degree day model to cotyledon weeds and increase herbicide rates in each sequential application based upon the sugarbeet stage. Do not be afraid to hire an aerial applicator if weather does not permit ground application. Timing of sequential postemergence applications to sugarbeet is nearly as important as the initial application.

The hot water used for preslurring UpBeet and the spray solution should be adjusted to a pH of 8 to 9 to maximize the solubility and subsequent activity of UpBeet. The highest legal amount of Nortron must be applied per application if kochia is present to improve control. If ACCase-resistant wild oat is known to occur or is suspected, apply the highest rate of Select for a single application when tank-mixing with the broadleaf herbicides or apply Select alone at a high single use rate one day prior to the broadleaf herbicides.

Roundup Ready sugarbeet

For Roundup Ready sugarbeet, apply glyphosate at 1.125 lb ae/A plus non-ionic surfactant at 0.25 to 1%v/v (depending upon the formulation) plus AMS at least at 8.5 lb/100 gallon of spray mixture to 1" weeds, before four-leaf sugarbeet, or when the spring cover crop has 3 leaves. Applying the maximum rate of glyphosate in a single application to Roundup Ready sugarbeet and including nonionic surfactant is necessary if temperatures remain cool, lambsquarters are present in the field, and/or difficult to control weeds are present. If ragweed, wild buckwheat, volunteer soybean, and/or dandelion are present include Stinger at 2 to 4 fl oz/A with the glyphosate and repeat the mixture in the second application. Wild buckwheat and dandelion require the higher use rate. If glyphosate-resistant waterhemp is present include Betamix at 1 pt/A plus Nortron at 4 fl oz/A plus MSO that is friendly to glyphosate at 1.5 to 2 qt/A with the glyphosate to improve control. Repeat this mixture as necessary. Subsequent glyphosate applications should be made every 14 to 21 days to weeds less than 2" in height. Consult the NDSU Weed Science website and look under sugarbeet weed control for information about glyphosate formulations labeled for Roundup Ready sugarbeet in 2011.

Links to sugarbeet weed control recommendations:
Sugarbeet Weed Control
North Dakota Weed Control Guide - 2011
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