Iowa Farmers Are Concerned About Herbicide-Resistant Weeds

New ISU survey shows farmers in Iowa are changing their weed management practices to deal with this issue.

Published on: Dec 11, 2013

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," says 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 sociologist.

They developed the herbicide resistance questions for the 2013 poll in partnership with the ISU Department of Agronomy. Associate chair of the department, Mike Owen, who is an agronomy professor and an ISU Extension weed specialist, says 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.

WORRIED ABOUT WEEDS: Iowa farmers are increasingly concerned about herbicide-resistant weeds and are changing their weed management practices to deal with the problem, according to the 2013 Iowa Farm and Rural Life Poll. "Typically growers dont realize they have an herbicide resistance problem until 30% of the weeds are of the resistant phenotype," says ISUs Mike Owen. Of the farmers responding to the poll 35% reported they had weeds they believed to be resistant to at least one herbicide group.
WORRIED ABOUT WEEDS: Iowa farmers are increasingly concerned about herbicide-resistant weeds and are changing their weed management practices to deal with the problem, according to the 2013 Iowa Farm and Rural Life Poll. "Typically growers don't realize they have an herbicide resistance problem until 30% of the weeds are of the resistant phenotype," says ISU's Mike Owen. Of the farmers responding to the poll 35% reported they had weeds they believed to be resistant to at least one herbicide group.

"Typically growers don't realize they have an herbicide resistance problem until 30% of the weeds are of the resistant phenotype," says Owen. He discussed the poll last week during his presentation to farmers, crop consultants and others at ISU's annual Integrated Crop Management Conference in Ames.

Glyphosate resistance was most commonly cited, with 32% of Iowa farmers saying they have glyphosate resistant weeds

Arbuckle says 35% 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% of farmers reporting glyphosate-resistant weeds. Another 14% of farmers reported they had weeds they believed to be resistant to ALS inhibitor herbicides. Only 5% or fewer reported weeds resistant to triazine, HPPD inhibitor or PPO inhibitor herbicides.~~~PAGE_BREAK_HERE~~~

Also, 52% of respondents indicated 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% indicated that they hired custom applicators to do at least some of their spraying.

Ninety percent of respondents reported they used postemergence herbicides in 2012, and 64% applied them to more than 75% of their land. Eighty-five percent reported using soil-applied herbicides, with half of farmers applying them to more than 75% of their cropland. Eighty-one percent indicated they used formal scouting methods to determine the need for postemergence spraying on at least some of their land.

How effective are your management practices for managing herbicide-resistant weeds?

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% used multiple herbicide application timings. Seventy-four percent of farmers also had managed weeds using tillage, 71% had used multiple modes of herbicide action in a season and 60% 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 notes. "More than 80% of farmers rated crop rotation and multiple herbicide application timings as effective or very effective. At least 70% rated tillage or multiple modes of herbicide action used in a season or in each application as effective or very effective management strategies."

Growers still need to realize there are a lot of tactics they can use to manage herbicide resistant weeds

The 2013 Iowa Farm and Rural Life Poll "gives us a snapshot 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 says.~~~PAGE_BREAK_HERE~~~

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.

About the Iowa Farm and Rural Life Poll: Arbuckle says 1,209 farmers participated in the 2013 Farm Poll and on average they were 65 years old. Because the Farm Poll is a panel survey, in which the same farmers participate in multiple years, participants are somewhat older on average than the general farmer population. Fifty-two percent earned more than half of their income from farming, while an additional 17% earned between 26% and 50% of their household income from the farm operation.

In addition to herbicide resistant weeds, the 2013 Iowa Farm and Rural Life Poll asked for farmers' opinions on climate change, rented land, Bt-resistant corn rootworm, and soil health and compaction.

The 2013 Iowa Farm and Rural Life Poll summary report (PM 3061) and previous Iowa Farm and Rural Life Poll summary and topical reports are available to download from the ISU Extension and Outreach Online Store and Extension Sociology.

Conducted every year since its establishment in 1982, the Iowa Farm & Rural Life Poll is the longest-running survey of its kind in the nation. ISU Extension, the Iowa Ag & Home Economics Experiment Station, the Iowa Department of Agriculture & Land Stewardship, and the Iowa Ag Statistics Service are all partners in the Farm Poll effort.