Herbicide-resistant kochia invading Texas High Plains

Kochia, a kind of tumbleweed, has long been associated with the Texas High Plains, but its abundance is starting to alarm Texas A&M AgriLife officials as regional producers are experiencing challenges controlling kochia as herbicide resistance is mounting.

 

Muthu Bagavathiannan, Ph.D., Texas A&M AgriLife Research weed scientist in the Texas A&M Department of Soil and Crop Sciences, College Station, said kochia has been a major multiple herbicide-resistant weed problem for some time in parts of the Great Plains – Kansas, Colorado, Montana and surrounding states, and even in Canada.

 

 

Kochia is a summer annual plant, germinating in the spring and maturing in the fall. It is often the first weed species to germinate in the soil each spring, Bagavathiannan said. Thousands of seeds are produced on one plant and spread into the soil when the weed breaks free and begins to tumble.

 

 

The path of resistant kochia can be seen where it rolled across this no-till wheat-fallow field near Dumas. (Texas A&M AgriLife photo by Muthu Bagavathiannan)

 

The tumbling ability is an important dispersal mechanism for this weed, which can rapidly spread herbicide-resistant genes across agricultural landscapes, he said. It is common to see kochia tumbleweeds get caught up in fence lines, and the dropped seed establishes a patch along the field edges and ditch banks.

 

 

These patches are usually not well managed, leading to further spread into adjacent crop fields and pasture lands, Bagavathiannan said.

 

 

Jourdan Bell, Ph.D., Texas A&M AgriLife Extension Service agronomist, Amarillo, said where kochia is sprayed along a fence line, producers often use a non-selective burndown herbicide and overspray  into the highway right of way. This can result in bare soil along the highway right of way and a perfect environment for weeds to proliferate. If the kochia patches are already resistant to glyphosate, it further magnifies the problem.

 

Resistance is a major concern, Bell said, because without effective management of kochia and other weeds, producers can see a big effect on their yields. In her research, she has seen up to an 80-bushel-per-acre difference between a corn plot with well-controlled weeds and an untreated control plot due to the resources being wasted by weeds.

 

 

Kochia tumbleweed caught on fence lines and establishing along the edge of a winter wheat field. These are not usually managed. (Texas A&M AgriLife photo by Muthu Bagavathiannan)

 

Bell said she has received multiple calls from farmers in the area who faced kochia control failures with glyphosate, dicamba, metsulfuron and fluroxypyr and suspect multiple resistance to these herbicides.

 

Kochia is also found increasingly common in cotton and grain sorghum fields and fence lines in the South Plains.

 

“Though effective control has not been an issue so far in the area, we are beginning to monitor its spread and paying close attention to its response to herbicides,” said Peter Dotray, Ph.D., AgriLife Research weed scientist, Lubbock. “The key to effective kochia control is timeliness of preplant applications when weeds are very small.”

 

 

Bagavathiannan said he conducted a survey in the Texas High Plains in 2018 to start documenting the distribution of kochia and determine herbicide resistance status. He said he frequently observed kochia in winter wheat-fallow fields, especially in no-till systems, a pattern consistent with the Great Plains states. He also found corn, grain sorghum and cotton fields with severe infestations of this weed.