Pigweed emerging as farmers? super pest

Pigweed, with its ability to quickly adapt genetically, has developed Roundup herbicide resistance nearly as quickly as the crops altered by scientists to do so.

Researchers at Kansas State University said pigweed not only has an ability to alter genetics at a fast rate when faced with threats, but it can also cross among several varieties in this region to create new hybrids.

The persistence of pigweed, a soil sapping broad?leaf, is evident in Marion County fields of various crops even though farmers use various techniques to control it.

K-State literature identifies several pigweed varieties in this area that can contribute genetics for change including redroot pigweed, smooth pigweed, Powell amaranth, spiny amaranth tumble pigweed, protrate pigweed, common water hemp, tall water hemp and Palmer amaranth.

So, if you travel to a friend?s farm in a different locale, and notice that his pigweed infestation looks a little different than yours, you?re probably right. A different pigweed hybrid may have developed there according to K-State Extension. But it could contribute genetics to your pigweed problem in the future.

Research at K-State has confirmed that efforts to adapt pigweed as a low value woody and stemmy hay crop are unlikely to succeed because it is toxic to livestock from cattle and horses to goats. It?s a plant focused on preserving itself.

Jeff Mayfield, agronomist with Ag Service Inc. in Hillsboro, said strains of pigweed adapted to certain situations such as high heat and drought can wait as seed in the ground without germinating until those conditions prevail.

Mayfield said if a producer sees ?tremendous pigweed pressure? that he didn?t see in past years, ?it probably isn?t because he brought in unwanted pigweed seed from another location. It?s because the seed has been waiting in the ground for a long time,? he said.

?Pigweed seed can lay in the ground up to 30 years before germinating.?

Just because pigweed has altered itself along with genetically altered soybeans and corn to be resistant to glycophosphates, the generic term for herbicides first marketed as Roundup, doesn?t mean it also can?t develop resistance to other herbicides.

Mayfield said pigweed has developed resistance to 2-4D, a herbicide that was used for nearly a half century.

Part of the solution for dealing with pigweed may come from using different herbicides at different times and in different mixes, Mayfield said.

K-State researchers used a tour last fall at Salina to illustrate treatment for pigweed in wheat stubble after harvest.

At that time, Dallas Peterson, weed control specialist at K-State, said the pigweed problem has reached a point where glyphosates are no longer an effective treatment against them.

In varying trials at Gyp?sum, the K-State researchers found varying mixes of herbicides to deal with pigweed.

It?s recommended that you check with your herbicide provider to find what mixes are working best in your area.

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