Iowa farmers are increasingly concerned about herbicide-resistant weeds and are changing their weed management practices to deal with the issue, according to the 2013 Iowa Farm and Rural Life Poll.
“In this year’s poll, we directed herbicide resistance questions to farmers who planted corn, soybeans or other row crops in 2012,” said J. Gordon Arbuckle Jr., a sociologist with Iowa State University Extension and Outreach. Arbuckle co-directs the annual poll with Paul Lasley, also an ISU Extension and Outreach sociologist.
The sociologists developed herbicide resistance questions for the 2013 poll in partnership with the ISU Department of Agronomy. Associate Chair Micheal Owen, university professor and extension weed specialist, said they wanted to gather in-depth information about the state of herbicide resistance in Iowa. They hoped to reveal farmers’ impressions of herbicide resistance and gain insight into the weed management practices farmers might be using.
“Typically growers don’t realize they have an herbicide resistance problem until 30 percent of the weeds are of the resistant phenotype,” Owen said.
Arbuckle said 35 percent of farmers responding to the poll reported they had weeds they believed to be resistant to at least one herbicide group. Glyphosate resistance was most commonly cited, with 32 percent of farmers reporting glyphosate-resistant weeds. Fourteen percent of farmers reported they had weeds they believed to be resistant to ALS inhibitor herbicides. Only 5 percent or fewer reported weeds resistant to triazine, HPPD inhibitor or PPO inhibitor herbicides.
Fifty-two percent of respondents indicated that they had changed their weed management program in the past five years to address herbicide-resistant weeds. Less than half reported that they developed their own herbicide programs, and 65 percent indicated that they hired custom applicators to do at least some of their spraying.
Ninety percent of respondents reported that they used postemergence herbicides in 2012, and 64 percent applied them to more than 75 percent of their land. Eighty-five percent reported using soil-applied herbicides, with half of farmers applying them to more than 75 percent of their cropland. Eighty-one percent indicated that they used formal scouting methods to determine the need for postemergence spraying on at least some of their land.
The researchers also asked farmers whether they used particular management practices and how effective those practices were for managing herbicide-resistant weeds.
Ninety-three percent used crop rotation and 80 percent used multiple herbicide application timings. Seventy-four percent of farmers also had managed weeds using tillage, 71 percent had used multiple modes of herbicide action in a season and 60 percent had used multiple modes of herbicide action in each application.
“These most commonly used strategies for managing herbicide-resistant weeds were also rated as the most effective,” Arbuckle said. “More than 80 percent of farmers rated crop rotation and multiple herbicide application timings as effective or very effective. At least 70 percent rated tillage or multiple modes of herbicide action used in a season or in each application as effective or very effective management strategies.”
The 2013 Iowa Farm and Rural Life Poll “provides us with a snap shot of how agriculture in Iowa is understanding and addressing issues regarding herbicide resistance. Researchers still have a lot of work to do before growers are fully aware of the serious issues. Growers can learn there are a lot of tactics they can use,” Owen said.
The weed specialist noted that more analyses of the farm poll data would be useful. How did growers with 1,000 acres or more respond compared with growers on smaller farms? Did they use different tactics? Getting answers to those types of questions could be helpful in developing ISU Extension and Outreach education programs.
Source : iastate.edu