Waterhemp Population in Central Illinois Seed Corn Production Field Resistant to HPPD-Inhibitor Herbicides

Awaterhemp population in a central Illinois seed corn production field has been found resistant to several commercially available HPPD-inhibitor herbicides. Last year, the field contained waterhemp populations that were not controlled by foliar-applied HPPD-inhibitor herbicides.
 
Syngenta greenhouse testing has confirmed resistance in this waterhemp population to several post-emergence applied HPPD-inhibitor herbicides including mesotrione, available as Callisto® herbicide. In addition, Syngenta field studies showed ineffective weed control with post applications of HPPD inhibitors, and ineffective control with post applications of some ALS and triazine herbicides applied alone to the same population.
 
Syngenta field studies showed that pre-emergence applications of HPPD inhibitors Lumax® and Lexar® (containing mesotrione, S-metolachlor and atrazine) provided effective control of this waterhemp population.
 
"This particular field was used for seed corn production, and for seven consecutive years there was over-reliance on certain post-emergence HPPD-inhibitor herbicides to control key weeds,” said Chuck Foresman, manager of weed resistance strategies for Syngenta. “Hybrid seed corn production systems often preclude the use of important broad-spectrum herbicides like glufosinate or glyphosate. The lack of diversity in both herbicide modes of action and crop rotation in this field led to the development of resistant waterhemp.”
 
In Syngenta field tests, the following products applied post-emergence also controlled the population: 1) PPO-inhibiting herbicides, available as Flexstar® and Prefix® herbicides; 2) certain glufosinate and auxin containing herbicides; and 3) glyphosate, available in Touchdown®, Flexstar GT and Halex® GT herbicides. The multiple modes of action in Flexstar GT (fomesafen and glyphosate) and Halex GT (S-metolachlor, mesotrione and glyphosate) work to reduce selection pressure and help delay the onset of weed resistance.
 
"At Syngenta, we are dedicated to sound weed resistance management and took immediate action to understand this non-performance issue,” Foresman said. “We are working with the University of Illinois, local dealers and farmers on proper stewardship.”
 
The HPPD-inhibitor technology is important for farmers as they continue to work to meet the demands of an ever growing population. To preserve this important technology, Syngenta recommends proactive resistance management practices including rotating modes of action and crops, using full herbicide rates, tank mixing herbicides with multiple modes of action, as well as appropriate cultural practices like tillage and cover crops to reduce selection pressure.
 
Syngenta has led the fight against glyphosate resistance, having first recognized the evolution of this challenge in 2001. The company’s extensive stewardship program includes working with university research and extension, developing premixes of key herbicides in corn, soybeans and cotton, and providing best weed management practices to delay the onset of resistance.
 
Syngenta is one of the worlds leading companies with more than 25,000 employees in over 90 countries dedicated to our purpose: Bringing plant potential to life. Through world-class science, global reach and commitment to our customers, we help to increase crop productivity, protect the environment and improve health and quality of life. For more information about us please go to www.syngenta.com.

source: Syngenta news release