MORE: Weed Resistance Means New Control Strategies

Northwest Iowa — A strategy for dealing with weeds that came out about 20 years ago has worked great for several years, but now farmers may have to do something else.
tall waterhemp herbicide resistant
The strategy has more than one name, but is normally called “Roundup Ready.” Roundup is a glyphosate herbicide that when it was released by Monsanto in the 1970’s basically killed all plants including crops. The strategy changed when strains of crops were developed that were resistant to the glyphosate. Since the patent expired on Roundup in 2000, other companies have also made glyphosate.

Iowa State University Extension Crop Field Specialist Joel De Jong says that now the problem is, weeds are developing resistance to the product as well.

De Jong says farmers should consider diversifying their herbicide program.

He says the Roundup Ready and similar products have a history of good performance.

De Jong says the main weed that has become resistant is waterhemp, with some mares tail in this area. He says that sometimes experts suggest switching herbicides and sometimes they suggest adding additional herbicides.

He says some farmers are going back to increased tillage such as cultivating to manually defeat the weeds.

He says they’re also looking at reducing row spacing so there are more crop plants so the weeds can’t grow so easily. He says they’re talking about spraying a pre-emergence herbicide and then coming back later with a post-emergence one in a timely basis.

De Jong tells us how ISU Extension has been helping farmers make weed control decisions.

For more information about weed resistance and what farmers can do about it, contact your local extension office.

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