It may pay to make an extra effort to control glyphosate resistant kochia in harvested wheat fields – especially if you plan to rotate to Roundup Ready soybeans, says Mike Moechnig, South Dakota State University Extension weed specialist.
Resistant kochia was seen in many fields during the growing season. They will likely continue to grow even after being sprayed with glyphosate after wheat is harvested.
To control resistant kochia in stubble, you may have to apply products that contain fluroxypyr (Starane and several others), bromoxynil (Bronate and serveral others), or dicamba, Moechnig says. 2.4-D is generally not very effective.
Also, drought conditions may reduce herbicide activity, but adding a surfactant may slightly increase weed control, Moechnig says.
If planting cover crops, these herbicides may not be restrictive for planting most species. More information on the effects of tank mix partners on cover crops may be found at www.Mikesweeds.com on the "small grains" page.
Getting kochia under control in wheat stubble is important because kochia seed has very little dormancy. Aggressive management will likely deplete the seed bank and make weed management in soybeans much easier, Moechnig says.