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Test of weeds for glyphosate resistance will take 3 months

Sean Ellis

Capital Press

It could take at least several weeks before researchers know for sure whether weeds found growing in two Roundup Ready sugar beet fields in the Treasure Valley area have in fact developed resistance to glyphosate.

It will be about three months before researchers know for sure whether kochia weeds that survived after being sprayed with Roundup have developed resistance to glyphosate, a weed killer that is the active ingredient in the herbicide.

In the meantime, the researcher who alerted western Idaho and eastern Oregon farmers to the possible case of glyphosate-resistant weeds in two Treasure Valley sugar beet fields is asking farmers to be on the lookout for further cases.

Kochia is a major weed problem in this region and researchers want to make sure they nip any potential problems in the bud, said University of Idaho weed scientist Don Morishita.

“We don’t want any of these plants to go to seed,” he said. “That can really spread quite rapidly.”

Morishita posted an alert June 11 after being contacted by growers who observed kochia weeds still growing in sugar beet fields that had been sprayed with Roundup, which is produced by Monsanto Corp.

The Roundup Ready sugar beets were genetically modified by Monsanto to be resistant to glyphosate.

University of Idaho plant breeder and geneticist Jack Brown said there are two ways a weed could develop resistance to a chemical such as glyphosate:

• Genes or characteristics from a glyphosate-resistant crop could be transferred to the weed via cross-pollination.

• A weed could also develop resistance through mutation.

Morishita said UI and Oregon State University researchers will collect the suspect weeds this week and transplant them into pots. They will then collect the seed, grow new plants and treat them with glyphosate to see if they have in fact developed resistance to the chemical.

He said it will take about four weeks to collect mature seed and another four weeks to grow out the harvested seed.

Including the time it takes to spray the new plants and see if they are resistant to glyphosate, “It will probably be about 12 weeks before we can know for sure,” Morishita said.

If glyphosate-resistant kochia weeds were to take root in this region, it would mean more expense for growers who plant Roundup Ready crops such as sugar beets and corn because they would have to use more chemicals to control it.

Kochia is widespread and found in all crops grown in this area, said Greg Dean, an Amalgamated Sugar Co. agronomist who covers most of western Idaho.

“Kochia is one of the bad ones,” he said.

There are other ways to fight glyphosate-resistant kochia, he said, but “it’s a complicated process and there would be additional expenses in continuing to manage it.”

Morishita encouraged growers to report any instances of kochia surviving after being sprayed with Roundup to their local crop consultant or extension educator.

Trent Clark, Monsanto’s public and government affairs director, said there are several possible explanations for the weeds’ survival that don’t involve any genetic changes in the plant and he cautioned against jumping to any conclusions before testing is completed.

Brown agreed.

“There are a number of scenarios that could explain this situation,” he said. “It is premature to say those weeds have developed resistance to glyphosate.”

Former Idaho farmer Doug Jones, executive director of Growers for Biotechnology, said kochia is one of the tougher weeds and “kochia would be high on my suspect lists of weeds that could evolve to be resistant to a herbicide.”

But, he added, “It also could have just been a miss … or a plugged nozzle on a sprayer. Spraying is a science but it’s also an art to get everything covered.”

Don Huber, the former Purdue University professor who has called for a moratorium on glyphosate-resistant crops until more research is done, said some weeds in the South and Midwest have developed resistance to glyphosate.

He said that can probably be attributed to the extensive use of the chemical.



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