Lab Analysis Tests Resistant Weeds

Published online: Jul 14, 2014 Herbicide Sean Ellis, Capital Press
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ONTARIO, Ore. — It could be several weeks instead of a few months before researchers know for sure whether some kochia weeds in the Treasure Valley area in Idaho have developed resistance to the weed killer glyphosate.

Sugar beet growers in Western Idaho and Eastern Oregon were alerted June 11 about the possibility of glyphosate-resistant kochia weeds after some of the weeds were observed growing in two sugarbeet fields that had been sprayed with the herbicide Roundup.

Glyphosate is the active ingredient in Roundup. The fields where the suspect kochia weeds were discovered were planted to Roundup Ready sugarbeets, which are genetically modified by Monsanto Corp. to resist glyphosate.

University of Idaho and Oregon State University weed scientists have transplanted some of the suspect plants into pots and will collect the seed, grow new plants and treat them with glyphosate to see if they have developed resistance to the chemical.

That process will take another two months. However, the researchers have also sent some of the suspect plants to a seed scientist at Montana State University who will do a lab analysis.

This will speed up the process of determining whether the weeds are in fact glyphosate-resistant by about a month, said UI weed scientist Don Morishita.

Regardless of whether the weeds are glyphosate-resistant, OSU is proceeding with a field trial at its Malheur County experiment station that seeks to determine the best treatment methods for controlling kochia in sugarbeet fields.

Glyphosate-resistant kochia weeds have already been found in several Midwestern states and it’s only a matter of time before they appear in this area as well, said OSU weed scientist Joel Felix, the lead researcher.

Felix said resistant kochia weeds could hitchhike here or develop in this area through natural selection.

“One way or another, it will come to us,” he said.

According to Felix and Morishita, weeds don’t mutate to develop resistance to a herbicide like Roundup. Instead, the product allows a very small population of the weeds that are naturally resistant to thrive because it kills off their competition.

“The product is selecting the plants within the population that are prone to resistance and getting rid of competition,” Felix said. “In time, you end up with only the resistant population building (up).”

One of the best ways to avoid selecting naturally resistant kochia weeds is to use different treatment combinations, Felix said, and the first-year trial is looking at treatment combinations in conjunction with Roundup.

Morishita said weed scientists have been emphasizing the importance of using different modes of action in conjunction with glyphosate to help avoid glyphosate-resistant weeds since Roundup Ready sugarbeets were first introduced.

There are a number of approaches growers need to be taking to preclude weeds from developing resistance to Roundup and “that includes using some other chemicals with Roundup,” said David Elison, an Amalgamated Sugar Co. agronomist.


Source: Capital Press