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Cranking Up the Heat

Thursday, April 1, 2010
filed under: Weeds

Though the sunflower grower’s herbicide toolbox is better equipped today than it was a decade ago, there still are — relative to crops like wheat, corn and soybeans —relatively few options for in-season weed management, especially if one is not growing a Clearfield® or ExpressSun® variety.

That situation underscores the importance of good weed control in preceding crops in the rotation — and the importance of spring preplant burndown treatments as well as fall burndown applications on the next year’s sunflower ground.

There are a variety of burndown options available to sunflower growers. Here’s a quick review of several options:

Glyphosate — Roundup® products and their now-numerous generic equivalents — are the obvious choice of many producers. The broadspectrum contact herbicide can be applied to control emerged weeds before or after sunflower planting but prior to crop emergence. Growers should refer to specific product labels for rate and adjuvant recommendations.

Paraquat — This restricted-use contact herbicide is registered for the control of emerged weed seedlings before, during or after planting but before the sunflower crop emerges.

Spartan — This “workhorse” herbicide provides several application options. Along with being used as a pre-emergence treatment by many sunflower growers, the product can be applied preplant incorporated up to 30 days prior to planting. A tank mix of Spartan and glyphosate gives excellent burndown control of most annual small-seeded broadleaf weeds and partial control of other annuals. Spartan also can be fall applied.

Spartan Charge® is designed for the no-till producer. Its formulation includes carfentrazone-ethyl (“Aim”) for faster preplant burndown of smaller-seeded broadleaf weeds like kochia. Spartan Advance® has glyphosate added to its formulation for broadspectrum preplant burndown for both no-till and conventional producers.

Valor® — The Valent product now has a label for use in fall and spring burndown programs to control emerged weeds and provide residual control. There is a minimum interval of 30 (2-oz rate) or 60 (3-oz rate) days between Valor application and the planting of sunflower. So that has translated into a fall application schedule for upcoming sunflower fields. To date, Valor typically has been applied in a tank mix with glyphosate and/or 2,4-D on those fields intended for sunflower the following spring. Tillage should be avoided following application of Valor, as it will reduce the herbicide’s residual weed control.

FirstStep® —Dow AgroSciences recently announced that EPA had approved registration of this new wheat and barley herbicide. “FirstStep combines preplant burndown with SoilActive technology, providing up to three weeks of lasting control of winter annual and early spring-germinating broadleaves,” Dow Agro states. Some of the weed species controlled are wild buckwheat, tansy mustard, wild mustard, chickweed and Roundup Ready canola. The herbicide “offers excellent rotational flexibility to several crops, including sorghum, soybeans and sunflower,” according to the company.

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