June 19, 2009

Weed scientists from six universities have joined forces to examine grower weed management practices and develop programs to evaluate and improve the sustainability of weed control in Roundup Ready® cropping systems. Called the Benchmark Study, this multi-state research project is now in its fourth year. Funding for the study has been provided by the Monsanto Company.

Benchmark Study Report 1: Long-Term Research Study Initiated to Improve the Sustainability of the Roundup Ready Technology

University weed scientists have been concerned that frequently used herbicide programs could affect the sustainability and effectiveness of weed control in Roundup Ready cropping systems. They reasoned that weed populations may shift to species that are more tolerant to glyphosate. Also, without proper management, the potential to select for weeds resistant to glyphosate could adversely impact the utility and life cycle of the weed management system on the farm.

Benchmark Study Surveys Farmers

The Benchmark Study began in the winter of 2005-2006 with a telephone survey of about 1200 growers from six states. Growers planting Roundup Ready corn, soybean or cotton for a minimum of three years were included in the survey. The survey evaluated

• tillage practices,
• herbicide use patterns,
• grower perceptions of weed pressure, and
• their problematic weeds before and after adopting Roundup Ready cropping systems.

Growers also were questioned about their awareness of and actions taken regarding weed resistance to glyphosate.

Survey results recently were published in a series of peer reviewed scientific papers in the journal Weed Technology. The university collaborators and Monsanto are releasing Summary Reports that highlight valuable information from each of the Benchmark Study scientific papers. We will share these in this and the next four issues of CropWatch.

Field Research Component

The Benchmark Study also includes field research which is currently in its fourth year. Approximately 150 growers in six states were randomly selected from among the survey respondents to participate in on-farm trials. In each trial, the growers' current herbicide program is compared to a herbicide program recommended by university weed scientists.

The researchers expect that the herbicide program recommended by the university would reduce the potential risk of selecting for glyphosate resistance. They have been monitoring weed populations, weed species diversity, weed seedbank, crop yields, and economic returns from both herbicide programs throughout each growing season.

This information is currently being reviewed and evaluated and the weed scientists expect to publish results from the first two years of the field study in late 2009. The results of the Benchmark Study may provide valuable data comparing the sustainability of growers' current weed management programs to more diversified weed management programs, while reducing the risk of selecting for weed resistance to glyphosate.

Robert Wilson
Mark Bernards
UNL Extension Weed Specialists with the Benchmark Study