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Misuse of glyphosate short-sighted risk

An article or so ago I stated that I would get off the glyphosate resistance and Palmer pigweed topics to give you a break. I changed my mind.

The winter period is when growers are planning for next year. If I can just in some small way influence some growers to increase their efforts on resistance management, it will be worthwhile.

I hope it is obvious I have a passion for trying to help preserve our Roundup Ready crop technology. If we continue down the path we are headed, a lot of folks are going to look back in a few years and ask, “why were we so short-sighted?”

For me as a private consultant in a regional popular press article to say I feel glyphosate resistance is a threat to global food production may not get the attention of many people. I am going to attempt to ratchet that up a notch.

A paper by Todd Gaines and other researchers in Australia has just been published online in the U.S. Journal PNAS. The title is “Gene amplification confers glyphosate resistance in Amaranthus palmeri.”

In our terms Amaranthus palmeri is Palmer pigweed and this paper documents yet another evolved mechanism of pigweed resistance to glyphosate. The online address for the article is

In a recent email, Stephen B. Powles from the University of Western Australia (I consider him the world’s foremost authority on herbicide resistance) sent out a personal commentary entitled “Gene Amplification Delivers Resistant Weed Evolution.” That commentary will also be published in the PNAS online journal.

I wish to pass along some of the points from Powles’ commentary. In plants, glyphosate is toxic because it inhibits a specific enzyme pathway (EPSPS). To date, resistant weeds either exhibit a mutation at the enzyme level or a trait that restricts glyphosate movement to that enzyme.

With gene amplification, the weeds evolve to massively overproduce the EPSPS enzyme due to continued selection pressure from overuse of glyphosate. In Powles’ terms, the overproduction of the enzyme acts like a molecular sponge to soak up the herbicide and continue to function normally in the plant.

With that I have told you far more than I know and I am sure you wish to read. The point is the glyphosate resistance snowball continues to pick up speed. Since Arkansas is ground zero for Palmer pigweed, we are right in the middle of it.

In his commentary, Powles said glyphosate resistance evolution is a threat to world food production. He called glyphosate “a one in 100 year discovery that is as important for reliable global food production as penicillin is for battling disease.”

In some personal correspondence he said that “twenty years from now this will be in the textbooks as a classical case of a great technology being driven to redundancy by over-use.”

I share his passion as a weed science professional to keep trying to get the word out. I keep asking, “Why are we doing this?”

The science in the articles and commentary cited above is beyond my understanding. What I do understand is the train wreck can only be stopped at the grower level. All of the complicated science boils down to whether or not individual farmers are willing to invest in the diversity necessary to reverse the trend.

In some fields it is too late. However, the majority of the situations can either be prevented or salvaged if we just wake up.

The comment I hear constantly now is, “I was considering making some changes in my program, but with this cheap glyphosate I can not afford to.” I would submit that you can’t afford not to.

Without a serious increase in crop diversity, herbicide diversity and technology diversity on the part of every farmer, before long it won’t matter if they give you the glyphosate!


TAGS: Management
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