Herbicide rotation just as important as crop rotation for sunflowers

By Jennifer M. Latzke

Kansas has historically been known as the Sunflower State. But with the recent confirmation of populations of glyphosate-resistant Palmer amaranth in the state, the most recognizable state symbol could someday be a weed. That poses a problem for sunflower growers.

"One of the major needs expressed by growers over the last four or five years is the need for better broadleaf weed control in sunflowers," said Phil Stahlman. "Palmer amaranth is a growing concern in sunflowers and kochia as well." Stahlman is a weed scientist at the Kansas State University Agricultural Research Center in Hays, Kan.

In fact, he said, in addition to the widespread presence of glyphosate-resistant kochia throughout western Kansas, there are limited pockets of glyphosate-resistant Palmer amaranth in parts of central Kansas. And there are even some populations of Palmer amaranth that are resistant to the HPPD class of herbicides, such as Callisto, Impact or Armezon, and Laudis.

Typically, a sunflower grower would ensure that his field was clan before planting, using a glyphosate burndown, but with glyphosate resistance in weeds, he needs to have other options available. And that doesn't mean just a crop rotation, he added.

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