News Release 

Researchers find waterhemp has evolved resistance to 4 herbicide sites of action

A research study featured in the journal Weed Science provides worrisome new details about the evolution of herbicide resistance in waterhemp

Cambridge University Press

WESTMINSTER, Colorado - September 13, 2019 - A research study featured in the journal Weed Science provides worrisome new details about the evolution of herbicide resistance in waterhemp - an annual weed that represents a significant threat to Midwest corn and soybean crops.

When a waterhemp biotype in eastern Nebraska survived a post-emergent application of the PPO inhibitor fomesafen, a team of university scientists decided to take a close look. They discovered the population was resistant to four distinct herbicide sites of action, including PPO inhibitors, ALS inhibitors, EPSPS inhibitors and PS II inhibitors.

Among their findings:

  • All samples of the resistant waterhemp biotype tested positive for an ?G210 mutation in the PPX2L gene.
  • The population exhibited a four- to six-fold resistance to PPO-inhibiting herbicides, a three-fold resistance to EPSPS inhibitors (glyphosate) and a seven-fold resistance to atrazine (a PS II inhibitor).
  • When the ALS inhibitors chlorimuron and imazethapyr were applied at 32 times the label application rate, they achieved a less than 80 percent reduction in the aboveground biomass of the resistant waterhemp biotype.

"Our study showed there simply are no effective post-emergent herbicide choices for the control of resistant waterhemp in either glyphosate-resistant or conventional crops," said Debalin Sarangi, a postdoctoral researcher at the University of Nebraska-Lincoln. "Growers will need to diversify their approaches to weed management and complement the use of chemicals with cultural and mechanical controls."

###

To learn more, read the article "Protoporphyrinogen Oxidase (PPO) Inhibitor-Resistant Waterhemp (Amaranthus tuberculatus) from Nebraska is Multiple Herbicide-Resistant: Confirmation, Mechanism of Resistance, and Management." It is available online at www.cambridge.org/core/journals/weed-science.

About Weed Science

Weed Science is a journal of the Weed Science Society of America, a nonprofit scientific society focused on weeds and their impact on the environment. The publication presents peer-reviewed original research related to all aspects of weed science, including the biology, ecology, physiology, management and control of weeds. To learn more, visit http://www.wssa.net.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.