Wednesday, May 30, 2012

Weed Whac-A-Mole

The problem is called a money wasting nuisance. But as margins between world crop yield and continuing population growth have thinned, the margin is shrinking to the size of the nuisance. Should the nuisance grow just a little bit- goodbye margin.

We have tackled this subject before. It is the Roundup Ready seeds produced by Monsanto that are the issue in question. As Roundup (Glyphosate) use has gone from 4 million pounds in the year 2000 to 65 million pounds in 2011, Roundup resistant crops have multiplied.

The answer, according to Monsanto is to use a second type of weed killer along with the Roundup. They concede that the continued use of Gylcophate will lead to resistant weeds, it is unlikely that weeds will be able to develop resistance to two herbicides simultaneously.

While true in so far as it goes, this hope has proven to be optimistic.

Amy Coombs, The Scientist 20 May 2012 (Hat tip: NC)
The chance that a single mutation will confer herbicide resistance is 1 in 100,000, making the likelihood of a double resistant mutant less than 1 in a trillion. Early industry-sponsored research suggested resistance to glyphosate was particularly unlikely because large mutations in the herbicide’s target, the EPSPS enzyme, would render it dysfunctional, killing the plant before it could reproduce.
“The claims made were naïve, and resistant weeds have indeed developed,” says David Mortensen, a weed scientist at Pennsylvania State University. “When a chemical is applied to such a wide area—to nearly all soybean and cotton, and a big percentage of corn—the selection pressure is too intense.” …
[C]ombining chemicals doesn’t always work out as planned, says Patrick Tranel, a weed scientist at the University of Illinois. While doubling up on chemicals makes it unlikely that anything will survive, he says, it also “potentially increases the chance of selecting for a general mechanism that confers resistance to both herbicides.
…Weeds in nine different countries have independently developed resistance to multiple modes of action. Some stubborn survivors can now survive most of the chemicals used by farmers, and the infestations are spreading.
Despite the seemingly small odds of a plant evolving resistance to multiple herbicides, the dramatic increase in glyphosate-resistant weeds, which now infest more than 17 million acres nationwide, has made this possibility exponentially more likely. “We don’t need a single plant to undergo two unlikely adaptations—we just need one event to happen in a biotype that already has glyphosate resistance,” says Mortensen.

The hope is to come out with seeds that will be resistant to two herbicides, Monsanto introducing Glyphosate and Dicamba resistant seeds, and Dow Gyphosate and Herbicide 2,4-D.

It is hoped that the simultaneous application of herbicides will get around the problem of resistant weeds. This of course will mean a greater variety of chemicals will be sprayed on our food crops. It also begs the question: If there are already so many weeds out there that are resistant to Gyphosate, are they trying to close the stable doors after the horses have already escaped.


Anne said...

Yep. Crazy isn't it? 1 in 100,000 is not much when you consider that that many "weed" plants live along the edges of a few dozen feet of crop land.

Farmers have already been making their own chemical mixes by combining brands in the hopes to mitigate how many passes it takes to treat the fields.

russell1200 said...

The way plants naturally hyberdize that number shrinks even further.

I was reading a book about trees, and their speciazation and the author was saying that because of the way plants hyberdize it can be almost impossible to really say where a species begins or ends.

I have at least one each of 10,000 weed species in my little garden.