The best strategy for controlling glyphosate resistant kochia is to use a good crop rotation of at least three crops and to rotate herbicide chemistries in each crop, says Paul O. Johnson, South Dakota State University agronomy field specialist. In-season tillage can help, too, but it will only be a partial control. \
"The good news is that kochia seed only survives a few years in the soil, with the majority of it germinating the first year. After five years, most of the seed will be germinated and should be cleaned up – unless, of course, some kochia seed blows in from neighboring fields," he says.
Research on new herbicide resistance technologies includes work with dicamba and 2,4D, but these will not be available for at least a couple more growing seasons. "Keep in mind that in states near South Dakota, dicamba resistant kochia has been present for about 20 years and that 2,4-D is not very effective in controlling kochia," he says.
Kochia has been a weed of concern in South Dakota since the start of early agriculture, Johnson says. Kochia was first introduced in the United States as an ornamental around 1900. In the dry and droughty times it has even been put up for feed for livestock and its nickname is "poor man's alfalfa".
In the eighties, the concern of kochia's resistance to ALS herbicides changed some of the cropping patterns in the James River Valley part of South Dakota. In soybeans, the options to control kochia without the use of ALS herbicides were very limited. The best option that was left was the use of Cobra sprayed at the early stages of kochia growth, and even then control was only about 80 percent. The introduction of Roundup Ready Soybeans in 1996 gave producers a solution to kochia control.
South Dakota led the nation in the adoption of this technology. Furthermore, with the adoption of no-till, the landscape changed from a wheat and soybean rotation to a corn and soybean rotation. With the price and effectiveness of glyphosate, it became the herbicide of choice for both corn and soybeans. This worked well until 2009 when the first glyphosate resistant kochia was found in South Dakota.