Perspectives on herbicide resistance

Encyclopedia Article

Farmers and industry personnel attending a series of meetings in December completed a survey regarding their weed management practices and views regarding herbicide resistance. An earlier article described attendee opinions concerning the current distribution of herbicide resistant weeds in Iowa. This article describes their weed management practices and opinions on how herbicide resistant weeds might impact farming operations in the future. The participants in the survey may not be representative of all Iowa farmers and ag industry personnel.

The information regarding current herbicide use patterns was not surprising. Seventy percent of farmers reported using the same herbicide program on all of their corn acres, while 80% reported using the same program on all soybean acres. Glyphosate was applied postemergence to corn by 90% of the farmers, whereas 98% of farmers used glyphosate postemergence on their soybean. Nearly 50% of the farmers said they used preemergence herbicides on all of their fields.

Approximately 40% of the farmers attending the meetings reported using mechanical weed control on some of their corn and soybean acres. This is much higher than we would have expected, and probably somewhat skewed by the fact that the meeting in North Central Iowa had the most farmers in attendance. This region of the state is where mechanical weed control has remained the most popular. The dry weather during the 2012 growing season probably contributed to an increase in mechanical weed control due to reduced effectiveness of herbicides.

Of particular interest are the opinions of the participants on how herbicide resistant weeds may impact their operations in the near future (Table 1). Less than 5% of the farmers and industry participants stated that herbicide resistance would not be a problem for their operations. Nearly 45% of farmers believe they will be able to manage herbicide resistant weeds using currently available tools, whereas 37% believe they will need new technology to stay ahead of the problem. People in industry viewed herbicide resistance as a greater threat than farmers, with twice as many reporting that herbicide resistant weeds will force major changes in production practices.

Table 1. Projected impact of herbicide resistant weeds in the next five years.

  Farmers Industry
Resistance will not be a problem 3% 2%
Manage using currently available tools 43% 34%
Will need new herbicides/traits to manage 37% 30%
Will force major changes in production practices 17% 34%



  • Meaghan Bryan summarized the survey data.
  • Funding for this meeting series was provided by the United Soybean Board.

Prepared by Bob Hartzler

Iowa State Weed Science Online